Patent Application
20160060739
The present disclosure is directed to Ni-based Cr- and P-bearing metallic glasses containing small alloying additions of Nb and B, and optionally Si, capable of forming bulk glassy rods with diameters as large as 10 mm or more. The inventive bulk metallic glasses also exhibit very high strength and high toughness, and are capable of undergoing extensive macroscopic plastic bending under load without fracturing catastrophically. The inventive bulk glasses also exhibit exceptional corrosion resistance.
Amorphous Ni-based Cr- and P-bearing alloys have long been recognized as having enormous commercial potential because of their high corrosion resistance. (Guillinger, U.S. Pat. No. 4,892,628, 1990, the disclosure of which is incorporated herein by reference.) However, the viability of these materials has been limited because conventional Ni-based Cr- and P-bearing systems are typically only capable of forming foil-shaped amorphous articles, having thicknesses on the order of several micrometers (typically below 100 micrometers).
The thickness limitation in conventional Ni-based Cr- and P-bearing alloys is attributed to compositions that require rapid solidification (cooling rates typically on the order of hundreds of thousands of degrees per second) to form an amorphous phase. For example, Japanese Patent JP63-79931 (the disclosure of which is incorporated herein by reference) is broadly directed to Ni—Cr—Nb—P—B—Si corrosion-resistant amorphous alloys. However, the reference only discloses the formation of foils processed by rapid solidification, and does not describe how one would arrive at specific compositions requiring low cooling rates to form glass such that they are capable of forming bulk centimeter-thick glasses, nor does it propose that the formation of such bulk glasses is even possible. Likewise, United States Patent Application US2009/0110955A1 (the disclosure of which is incorporated herein by reference) is also directed broadly to amorphous Ni—Cr—Nb—P—B—Si alloys, but teaches the formation of these alloys into brazing foils processed by rapid solidification. Finally, Japanese Patent JP2001-049407A (the disclosure of which is incorporated herein by reference) does describe the formation of Ni—Cr—Nb—P—B bulk amorphous articles, but falsely advises the addition of Mo to achieve bulk-glass formation. Only two exemplary alloys capable of forming bulk amorphous articles are presented in this prior art, both containing Mo, and the bulk amorphous articles formed by the exemplary alloys are rods with diameters of at most 1 mm. Another two exemplary Ni—Cr—Nb—P—B alloys capable of forming glassy rods 1-mm in diameter are also presented in an article by Hashimoto and coworkers (H. Habazaki, H. Ukai, K. izumiya, K. Hashimoto, Materials Science and Engineering A318, 77-86 (2001), the disclosure of which is incorporated herein by reference).
The engineering applicability of these two-dimensional foil-shaped articles is very limited; applications are typically limited to coating and brazing. The engineering applicability of 1-mm rods is also restricted to very thin engineering components having sub-millimeter thickness. For broad engineering applicability, “bulk” three-dimensional articles with dimensions on the order of several millimeters are typically sought. Specifically, slab-shaped articles 1 mm in thickness, or equivalently (from a cooling rate consideration) rod-shaped articles 3 mm in diameter, are generally regarded as the lower limits in size for broad engineering applicability. Another requirement for broad engineering applicability is the ability of millimeter-thick articles to undergo macroscopic plastic bending under load without fracturing catastrophically. This requires that the bulk metallic glasses have relatively high fracture toughness. Accordingly, a need exists for Ni-rich Cr- and P-bearing alloys capable of forming bulk glasses.
The current disclosure is directed generally to the ternary base system Ni80.5−xCrxP19.5, where x ranges between 3 and 15. In certain aspects, Cr and P are replaced by small but well-defined amounts of certain alloying elements.
In one embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(69−w−x−y−z)Cr8.5+wNb3+xP16.5+yB3+z
where w, x, y, and z can be positive or negative, and where,
0.0494w2+1.78x2+4y2+z2<1
and wherein the largest rod diameter that can be formed with an amorphous phase is at least 5 mm.
In another such embodiment, the invention is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(69−w−x−y−z)Cr8.5+wNb3+xP16.5+yB3+z
where w, x, y, and z can be positive or negative, and where,
0.033w2+0.44x2+2y2+0.32z2<1.
and wherein the largest rod diameter that can be formed with an amorphous phase is at least 3 mm.
In a preferred embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(68.6−w−x−y−z)Cr8.7+wNb3.0+xP16.5+yB3.2+z
Here, an refined alloy composition is obtained when the variables w, x, y, and z are all identically 0. The values of w, x, y, and z (expressed in atomic percentages) can be positive or negative and represent the allowed deviation from the refined composition given by:
Ni68.6Cr8.7Nb3.0P16.5B3.2
and where these deviations (w, x, y, and z) satisfy the condition,
0.21|w|+0.84|x|+0.96|y|+1.18|z|<1.89
with |w|, |x|, etc. being the absolute value of the composition deviations, and wherein the largest rod diameter that can be formed with an amorphous phase is at least 3 mm.
In still yet another such embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(68.6−w−x−y−z)Cr8.7+wNb3.0+xP16.5+yB3.2+z
where w, x, y, and z can be positive or negative, and where,
0.21|w|+0.84|x|+0.96|y|+1.18|z|<1.05
and wherein the largest rod diameter that can be formed with an amorphous phase is at least 5 mm.
In still yet another such embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(68.6−w−x−y−z)Cr8.7+wNb3.0+xP16.5+yB3.2+z
where w, x, y, and z can be positive or negative, and where,
0.21|w|+0.84|x|+0.96|y|+1.18|z|<0.43
and wherein the largest rod diameter that can be formed with an amorphous phase is at least 8 mm. In another embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(100−a−b−c−d)CraNbbPcBd
where,
a is greater than 3 and less than 15,
b is greater than 1.5 and less than 4.5,
c is greater than 14.5 and less than 18.5, and
d is greater than 1 and less than 5;
and wherein the largest rod diameter that can be formed with an amorphous phase is at least 3 mm.
In another such embodiment, a is greater than 7 and less than 10, and the largest rod diameter that can be formed with an amorphous phase is at least 8 mm.
In another such embodiment, a is greater than 7 and less than 10, and the largest rod diameter that can be formed with an amorphous phase is at least 8 mm.
In still another such embodiment, a is between 3 and 7, and the stress intensity at crack initiation KQ, when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, is at least 60 MPa m1/2.
In yet another such embodiment, a is between 3 and 7, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm is at least 60 MPa m1/2, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In still yet another such embodiment, a is between 3 and 7, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In still yet another such embodiment, b is between 2.5 and 4.
In still yet another such embodiment, d is greater than 2 and less than 4, and the maximum rod diameter that can be formed with an amorphous phase is at least 5 mm.
In still yet another such embodiment, c+d is between 19 and 20.
In another preferred embodiment, the disclosure is directed to a metallic glass including an alloy represented by the following formula (subscripts denote atomic percent):
Ni(100−a−b−c−d)CraNbbPcBd
where,
a is greater than 2.5 and less than 15,
b is greater than 1.5 and less than 4.5,
c is greater than 14.5 and less than 18.5, and
d is greater than 1.5 and less than 4.5; and
wherein the largest rod diameter that can be formed with an amorphous phase is at least 4 mm.
In another such embodiment, a is greater than 6 and less than 10.5, b is greater than 2.6 and less than 3.2, c is greater than 16 and less than 17, d is greater than 2.7 and less than 3.7, and the largest rod diameter that can be formed with an amorphous phase is at least 8 mm.
In still another such embodiment, a is between 3 and 7, and the stress intensity at crack initiation KQ, when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, is at least 60 MPa m1/2.
In still another such embodiment, b is between 1.5 and 3, and the stress intensity at crack initiation KQ, when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, is at least 60 MPa m1/2.
In yet another such embodiment, a is between 3 and 7, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In yet another such embodiment, b is between 1.5 and 3, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In still yet another such embodiment, a is between 3 and 7, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In still yet another such embodiment, b is between 1.5 and 3, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In still yet another such embodiment, b is between 2.5 and 3.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 5 mm.
In still yet another such embodiment, d is greater than 2 and less than 4, and the maximum rod diameter that can be formed with an amorphous phase is at least 5 mm.
In still yet another such embodiment, c+d is between 18.5 and 20.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 5 mm.
In one embodiment, the disclosure is directed to an alloy represented by the following formula (subscripts denote atomic percent):
Ni(100−a−b−c−d−e)CraNbbPcBdSie
a is between 5 and 12,
b is between 1.5 and 4.5,
c is between 12.5 and 17.5,
d is between 1 and 5, and
e is up to 2;
In one such embodiment, a is greater than 7 and less than 10, and the stress intensity at crack initiation when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm is at least 60 MPa m1/2.
In another such embodiment, a is greater than 7 and less than 10, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In still another such embodiment, a is greater than 7 and less than 10, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In yet another such embodiment, b is between 2.5 and 4.
In still yet another such embodiment, d is between 2 and 4.
In still yet another such embodiment, e is up to 1.
In still yet another such embodiment, c+d+e is between 19 and 20.
In another preferred embodiment, the disclosure is directed to an alloy represented by the following formula (subscripts denote atomic percent):
Ni(100−a−b−c−d−e)CraNbbPcBdSie
where,
a is between 4 and 14,
b is between 1.8 and 4.3,
c is between 13.5 and 17.5,
d is between 2.3 and 3.9, and
e is up to 2; and
wherein the largest rod diameter that can be formed with an amorphous phase is at least 3 mm.
In one such embodiment, a is greater than 7 and less than 10, and the stress intensity at crack initiation when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm is at least 60 MPa m1/2.
In one such embodiment, b is greater than 1.5 and less than 3, and the stress intensity at crack initiation when measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm is at least 60 MPa m1/2.
In another such embodiment, a is greater than 7 and less than 10, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In another such embodiment, b is greater than 1.5 and less than 3, and the plastic zone radius rp, defined as (1/π)(KQ/σy)2, where KQ is the stress intensity at crack initiation measured on a 3 mm diameter rod containing a notch with length between 1 and 2 mm and root radius between 0.1 and 0.15 mm, and where σy is the compressive yield strength obtained using the 0.2% proof stress criterion, is greater than 0.2 mm.
In still another such embodiment, a is greater than 7 and less than 10, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In still another such embodiment, b is greater than 1.5 and less than 3, and a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In yet another such embodiment, b is between 2.5 and 3.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 4 mm
In still yet another such embodiment, d is between 2.9 and 3.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 4 mm.
In still yet another such embodiment, e is up to 1.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 4 mm.
In still yet another such embodiment, c+d+e is between 18.5 and 20.5, and the maximum rod diameter that can be formed with an amorphous phase is at least 4 mm.
In still yet another such embodiment, up to 1.5 atomic % of Nb is substituted by Ta, V, or combinations thereof.
In still yet another such embodiment, up to 2 atomic % of Cr is substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, Ti, Zr, Hf, or combinations thereof.
In still yet another such embodiment, up to 2 atomic % of Ni is substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, Ti, Zr, Hf, or combinations thereof.
In still yet another such embodiment, a rod having a diameter of at least 0.5 mm can undergo macroscopic plastic bending under load without fracturing catastrophically.
In still yet another such embodiment, the compressive yield strength, σy, obtained using the 0.2% proof stress criterion is greater than 2000 MPa.
In still yet another such embodiment, the temperature of the molten alloy is raised to 1100° C. or higher prior to quenching below the glass transition to form a glass.
In still yet another such embodiment, the Poisson's ratio is at least 0.35.
In still yet another such embodiment, the corrosion rate in 6M HCl is not more than 0.01 mm/year.
In one embodiment, the invention is directed to an alloy selected from the group consisting of: Ni69Cr8.5Nb3P17B2.5, Ni69Cr8.5Nb3P16.75B2.75, Ni69Cr8.5Nb3P16.5B3, Ni69Cr8.5Nb3P16B3.5, Ni69Cr8.5Nb3P15.75B3.75, Ni69Cr8Nb3.5P16.5B3, Ni69Cr7.5Nb4P16.5B3, Ni72.5Cr5Nb3P16.5B3, Ni71.5Cr6Nb3P16.5B3, Ni70.5Cr7Nb3P16.5B3, Ni69.5Cr8Nb3P16.5B3, Ni68.5Cr9Nb3P16.5B3, Ni68Cr9.5Nb3P16.5B3, Ni67.5Cr10Nb3P16.5B3, Ni66.5Cr11Nb3P16.5B3, Ni65.5Cr12Nb3P16.5B3, Ni68.5Cr9Nb3P16B3Si0.5, Ni68.5Cr9Nb3P15.5B3Si1, Ni69Cr8.5Nb3P16B3Si0.5, Ni69Cr8.5Nb3P15.5B3Si1, Ni69Cr8.5Nb2.5Ta0.5P15.5B3Si1, and Ni69.5Cr8.5Nb2.5Ta0.5P15.5B3Si1.
In another embodiment, the invention is directed to an alloy selected from the group consisting of: Ni72.5Cr5Nb3P16.5B3, Ni71.5Cr6Nb3P16.5B3, Ni70.5Cr7Nb3P16.5B3, Ni69.5Cr8Nb3P16.5B3, Ni68.5Cr9Nb3P16.5B3, Ni68Cr9.5Nb3P16.5B3, Ni67.5Cr10Nb3P16.5B3, Ni66.5Cr11Nb3P16.5B3, Ni65.5Cr12Nb3P16.5B3, Ni68.5Cr9Nb3P16B3Si0.5, Ni68.5Cr9Nb3P15.5B3Si1, Ni69Cr8.5Nb3P16B3Si0.5, and Ni69Cr8.5Nb3P15.5B3Si1.
In a preferred embodiment, the disclosure is directed to an alloy selected from the group consisting of: Ni69Cr8.5Nb3P17B2.5, Ni69Cr8.5Nb3P16.75B2.75, Ni69Cr8.5Nb3P16.5B3, Ni69Cr8.5Nb3P16B3.5, Ni69Cr8.5Nb3P15.75B3.75, Ni69Cr9Nb2.5P16.5B3, Ni69Cr8.75Nb2.75P16.5B3, Ni69Cr8.25Nb3.25P16.5B3, Ni69Cr8Nb3.5P16.5B3, Ni69Cr7.5Nb4P16.5B3, Ni72.5Cr5Nb3P16.5B3, Ni71.5Cr6Nb3P16.5B3, Ni70.5Cr7Nb3P16.5B3, Ni69.5Cr8Nb3P16.5B3, Ni68.5Cr9Nb3P16.5B3, Ni68Cr9.5Nb3P16.5B3, Ni67.5Cr10Nb3P16.5B3, Ni66.5Cr11Nb3P16.5B3, Ni65.5Cr12Nb3P16.5B3, Ni68.5Cr9Nb3P16B3Si0.5, Ni68.5Cr9Nb3P15.5B3Si1, Ni69Cr8.5Nb3P16B3Si0.5, Ni69.45Cr8.81Nb3.04P15.66B3.04, Ni69.03Cr8.75Nb3.02P16.08B3.12, Ni68.17Cr8.65Nb2.98P16.92B3.28, Ni67.75Cr8.59Nb2.96P17.34B3.36, Ni69Cr8.5Nb3P15.5B3Si1, Ni69Cr8.5Nb2.5Ta0.5P15.5B3Si1, and Ni69.5Cr8.5Nb2.5Ta0.5P15.5B3Si1.
In another such embodiment, the disclosure is directed to one of the following alloys: Ni68.6Cr8.7Nb3P16.5B3.2 or Ni68.6Cr8.7Nb3P16B3.2Si0.5.
Various examples of the present disclosure will be discussed with reference to the appended figures and data results, wherein:
Amorphous Ni-rich alloys bearing Cr and P were recognized as highly corrosion resistant materials more than twenty years ago (Guillinger, U.S. Pat. No. 4,892,628, 1990, cited above). However, conventional ternary Ni—Cr—P alloys were able to form an amorphous phase only in very thin sections (<100 μm) by processes involving either atom by atom deposition, like for example electro-deposition, or rapid quenching at extremely high cooling rates, like for example melt spinning or splat quenching. In the present disclosure, a Ni-rich Cr- and P-bearing alloy system having a well-defined compositional range has been identified that requires very low cooling rates to form glass thereby allowing for bulk-glass formation to thicknesses greater than 10 mm. In particular, it has been discovered that by minutely controlling the relative concentrations of Ni, Cr and P, and by incorporating minority additions of Nb and B as substitutions for Cr and P respectively, the amorphous phase of these alloys can be formed in sections thicker than 3 mm, and as thick as 1 cm or more. What is more, the mechanical and chemical properties of these alloys, including toughness, elasticity, corrosion resistance, etc. now become accessible and measurable, and therefore an engineering database for these alloys can be generated.
Accordingly, in some embodiments the metallic glass of the present disclosure comprises the following:
In various embodiments, the metallic glass is capable of forming an amorphous phase in sections at least 3 mm thick, and up to 10 mm or greater. In various alternative embodiments, the atomic percent of B in the alloys of the present disclosure is between about 2 and 4. In further embodiments, the combined fraction of P and B is between about 19 and 20 atomic percent. The atomic percent of Cr can be between 5 and 10 and of Nb between 2.5 and 4.
In some preferred embodiments, the metallic glass of the instant disclosure comprises the following:
As described above, the alloys of the instant disclosure are directed to five component or more Ni-based metallic glass forming alloys comprising some combination of at least Ni, Cr, Nb, P, and B. The 5-component system can be conveniently described by the formula:
Ni1-w-x-y-zCrwNbxPyBz
where the variables w, x, y, z are the concentrations of the respective elements in atomic percent. In conventional practice, alloys of this family are thought to have relatively poor glass-forming ability with a critical casting thickness of 1 mm or less. (See, e.g., JP 63-79931, JP-2001-049407A and US Pat. Pub. 2009/0110955A1, cited above.) However, it has now been discovered that by precisely refining the compositional variables within a fairly narrow range, an alloy of exceptional glass forming ability may be obtained. Such exceptional glass forming ability was neither taught nor anticipated in any of the prior art.
In particular, the present disclosure demonstrates that simultaneous substitutions of about 2 to 4 atomic percent P with B (Table 1 below, and
More importantly, it has been discovered that outside of the inventive ranges, the ability to produce the amorphous phase in bulk dimensions drastically diminishes. Moreover, the glass forming ability is shown to peak when Cr atomic concentration is between 8.5 and 9%, when the Nb atomic concentration is about 3%, when the P atomic concentration is about 16.5%, and when the B atomic concentration is between 3 and 3.5%, whereby fully amorphous bulk rods 10 mm in diameter or more are produced. calorimetry scans to determine the effects of increasing B at the expense of P, Nb at the expense of Cr, and Cr at the expense of Ni on the glass transition, crystallization, solidus, and liquidus temperatures were also performed (
In one embodiment, the inventive Ni-alloy composition can be described by a 4-dimensional composition space in which bulk amorphous alloy compositions with maximum rod diameter of 5 mm or larger will be included. In such an embodiment, a description of the alloy (based on the glass-forming ability vs. composition plots provided herein) would be an ellipsoid in a 4-dimensional composition space as described hereafter.
To form bulk amorphous alloys with maximum rod diameter of at least 5 mm, the alloys composition would satisfy the following formula (subscripts denote atomic percent):
Ni(69-w-x-y-z)Cr8.5+wNb3+xP16.5+yB3+z
where w, x, y, and z are the deviation from an “ideal composition”, are in atomic percent and can be positive or negative. In such an embodiment, for alloys capable of producing amorphous rods with diameter of at least 5 mm, the equation of the 4-dimensional ellipsoid would be given as follows:
(w/4.5)2+(x/0.75)2+(y/0.5)2+(z/1)2<1
or
0.0494w2+1.78x2+4y2+z2<1
If, for example, only w is considered (let x=y=z=0), the condition for 5 mm maximum rod diameter given by the “glass-forming ability vs. Cr content” plot of −4.5<w<4.5 is reached. In turn, if only x is considered (let w=y=z=0), the condition for 5 mm maximum rod diameter given by the “glass-forming ability vs. Nb content” plot of −0.75<x<0.75 is reached, etc. Accordingly, in this embodiment of the composition, the formula provides a preferred “5 mm” maximum rod diameter region since it treats the deviations as having a cumulative effect on degrading glass-forming ability.
In turn, the region that contains bulk amorphous alloys with maximum rod diameter of at least 3 mm can be obtained by adjusting the “size” of the ellipsoid. It is possible to obtain a formula for an alloy that can form amorphous rods at least 3 mm in diameter. This is given by an ellipsoid of the following formula (subscripts denote atomic percent):
Ni(69-w-x-y-z)Cr8.5+wNb3+xP16.5+yB3+z
where w, x, y, and z are the deviation from an “ideal composition”, are in atomic percent and can be positive or negative. In such an embodiment, for alloys capable of producing amorphous rods with diameter of at least 3 mm, the equation of the 4-dimensional ellipsoid would be given as follows:
0.033w2+0.44x2+2y2+0.32z2<1
In effect, the two formulae above provide a direct description of preferred embodiments of the inventive composition adjusted for the critical casting diameter desired.
In another embodiment, the present disclosure is also directed to Ni-based systems that further contain minority additions of Si. Specifically, substitution of up to 2 atomic percent P with Si in the inventive alloys is found to retain significant glass forming ability. As such, the Ni-based inventive alloys in this embodiment contain Cr in the range of 5 to 12 atomic percent, Nb in the range of 1.5 to 4.5 atomic percent, P in the range of 12.5 to 17.5 atomic percent, and B in the range of 1 to 5 atomic percent, and are capable of forming an amorphous phase in sections at least 3 mm thick, and up to 10 mm or greater. Preferably, the atomic percent of B in the alloys of the present disclosure is between about 2 and 4, and the combined fraction of P, B, and Si is between about 19 and 20 atomic percent. Also, the atomic percent of Cr is preferably between 7 and 10 and of Nb between 2.5 and 4.
Exemplary embodiments demonstrate that substitutions of up to about 2 atomic percent P with Si in the Ni68.5Cr9Nb3P16.5B3 system does not drastically degrade bulk metallic glass formation.
Accordingly, in some embodiments, the inventive Ni-alloy composition can be described by a 4-dimensional composition space in which bulk amorphous alloy compositions with maximum rod diameter of 3 mm or larger will be included. In such an embodiment, a description of the alloy (based on the glass-forming ability vs. composition plots provided herein) would be 4-dimensional “diamond shaped” region within a 4-dimensional composition space represented by the composition vector c=(w, x, y, z). As will be described below in detail, the refinement of the composition variables, based on an analysis of our experimental data on glass forming ability, yields a single precise alloy composition with maximum glass forming ability in the 5-component Ni—Cr—Nb—P—B system. This alloy can be formed into fully amorphous cylindrical rods of diameter of 11.5±0.5 mm (almost ½ inch) when melted at 1150° C. or higher in quartz tubes with 0.5 mm thick wall and subsequently quenched in a water bath. This precise refined composition is given by:
Ni1-w-x-y-zCrwNbxPyBz
where the variables (w, x, y, z) are the concentrations of the respective elements in atomic percent, and where the refined composition variables are w0=8.7 (at. % Cr), x0=3.0 (at. % Nb), y0=16.5 (at. % P), z0=3.2 (at. % B), and the balance of the alloy being 68.6 at. % Ni.
In the refinement of this alloy, the composition space along 4 independent experimental directions defined by 4 alloy “series” can be sampled as follows:
Ni77.5−uCruNb3.0P16.5B3.0 (Series 1)
Ni69Cr11.5−uNbuP16.5B3.0 (Series 2)
Ni69Cr8.5Nb3P19.5−uBu (Series 3)
(Ni0.8541Cr0.1085Nb0.0374)100-u(P0.8376B0.1624)u (Series 4)
These alloy series represent one-dimensional lines in the 4-dimensional composition space. The lines are oriented in 4 independent directions. Therefore any alloy composition in the vicinity of the refined composition can be formed by combining alloys belonging to the 4 alloy series. By demonstrating a sharp peak in glass forming ability in each separate alloy series, it can be inferred that there exists a single unique peak in the four-dimensional space, associated with one unique alloy composition which refines glass forming ability for the 5-component system.
The critical rod diameter data from
Following Iterative Refinement of each variable as described above, it is possible to identify the refined alloy composition and derive a general formula for any alloy in the neighborhood of the refined alloy composition. In accordance, it can be determined that refined alloy to be:
Ni68.6Cr8.7Nb3.0P16.5B3.2
In turn, the 4 experimental alloy series can be defined by the composition “shift” vectors around the refined composition:
Δu1=u×[1,0,0,0] (Cr replaces Ni)
Δu2=u×[−1,1,0,0] (Nb replaces Cr)
Δu3=u×[0,0,−1,1] (B replaces P)
Δu4=u×[−0.1085,−0.0374,0.8376,0.1624] (metalloids replace metals)
where u is the composition displacement in at. % along the specified alloy series.
Using the “standard’ composition variables (w, x, y, z) in the standard alloy formula Ni1-w-x-y-zCrwNbxPyBz, the four composition shift vectors (associated with displacements w, x, y, and z, are given by:
Δw=w×[1,0,0,0],
Δx=x×[0,1,0,0],
Δy=y×[0,0,1,0], and
Δz=z×[0,0,0,1].
These can be expressed in terms of the Δu's as:
Δw=Δu1,
Δx=0.7071Δu1+0.7071Δu2,
Δy=0.1423Δu1+0.0365Δu2−0.1586Δu3+0.9764Δu4, and
Δz=0.1110Δu1+0.0285Δu2+0.6379Δu3+0.7616Δu4.
Collecting these “fitting parameters”, the fit of the critical rod diameter data for the 4 alloy series gives two exponential “decay” parameters for each of the displacements Δu1, Δu2, Δu3, and Δu4 where the λi,± parameters are in “inverse decay” lengths (decay lengths in at. %) for positive (+ sign) and negative (− sign) deviations of composition from the refined values of each Δui. Glass-forming ability (GFA) is described along each series (i=1, 2, 3, and 4) by the formula:
GFA=D
—0+D—iexp[−λ_(±,i)Δu—i] (EQ. 1)
where the λ+,i and λ−,i parameters are determined from the fits presented in the charts for the series 1-4 shown in
Using these parameters and fits it is now possible to write a general formula for GFA in (w, x, y, z) coordinates. From the fitting it was found that using D0=1.5 mm for all of the u coordinates provided and excellent fit to the data. The values of the λ parameters in Table 5 were obtained with this value of Do. It was also found that the preferred value of Di=9.9 mm provided an excellent description of all of the data. This is the appropriate value of Di for all u coordinates (and therefore w, x, y, z coordinates) since all series must yield the same peak value of GFA. To an excellent approximation, GFA in the “standard coordinates” is:
GPA=D
0
+D
iexp[−λ±,w(w−w0)−λ±,x(x−x0)−λ±,y(y−y0)−λ±,z(z−z0)] (EQ.2)
where the λ± (for each coordinate) is chosen according to the sign of the displacements Δw=w−w0, Δx=x−x0, etc., and w0, x0, etc. refer to the refined composition variables. The values of the λ's are given in Table 5. The value of the “background GFA” is taken to be D0=1.5 mm while Di=9.9 mm is the best overall value which fits all data. This formula can be shown to provide an excellent description of the GFA of all experimental alloys studied in the Ni—Cr—Nb—P—B quinary glass system. The formula accurately predicts the GFA of any quinary alloy in the neighborhood with an accuracy of ±1 mm (maximum diameter for obtaining a fully amorphous rod). It should be noted that:
where D=9.9 mm. In other words, the reduction ln [(GFA−D0)/D] associated with composition errors are additive.
As such, according to the GFA equation and the additivity of logarithmic errors, it is possible to construct 4-dimensional composition maps for achieving a desired GFA. To illustrate this, simple 2-dimensional maps (projections from the 4-dimensional map) based on variations in two of the four independent variables (assuming the remaining variables are fixed at the refined values) are provided in
Accordingly, to form bulk amorphous alloys with maximum rod diameter of at least 8 mm or at least 5 mm, the deviations from refined alloy compositions must satisfy the following formula (subscripts denote atomic percent):
Ni(68.6−w−x−y−z)Cr8.7+wNb3.0+xP16.5+yB3.2+z
where w, x, y, and z are now taken to be the deviation from an “ideal composition”, are in atomic percent, and can be positive or negative, as shown in Table 6, below.
In such embodiments, for example, alloys capable of producing amorphous rods with diameter of at least 8 mm, the equation of the 4-dimensional “diamonds” would be given as follows:
0.21|w|+0.84|x|+0.96|y|+1.18|z|<0.43
with |w|, |x|, etc. being the absolute value of the composition deviations as above. If, for example, only w is considered (letting x=y=z=0), the condition for 8 mm critical rod diameter given by the “critical rod diameter vs. Cr content” plot (
In turn, the region that contains bulk amorphous alloys with maximum rod diameter of at least 5 mm can be obtained by adjusting the “size” of the 4-dimensional diamond. Using the data from
Ni(68.6−w−x−y−z)Cr8.7+wNb3+xP16.5+yB3.2+z
where w, x, y, and z are the deviation from an “ideal composition”, are in atomic percent and can be positive or negative. In such an embodiment, for alloys capable of producing amorphous rods with diameter of at least 5 mm, the equation of the 4-dimensional “diamond” would be given as follows:
0.21|w|+0.84|x|+0.96|y|+1.18|z|<1.05
Likewise, the region that contains bulk amorphous alloys with maximum rod diameter of at least 3 mm can be obtained by adjusting the “size” of the 4-dimensional diamond. Based on using the data from
Ni(68.6−w−x−y−z)Cr8.7+wNb3+xP16.5+yB3.2+z
where w, x, y, and z are the deviation from an “ideal composition”, are in atomic percent and can be positive or negative. In such an embodiment, for alloys capable of producing amorphous rods with diameter of at least 3 mm, the equation of the 4-dimensional “diamond” would be given as follows:
0.21|w|+0.84|x|+0.96|y|+1.18|z|<1.89
In effect, the two formulae above provide a direct and precise description of certain embodiments of the composition adjusted for the critical casting diameter desired. Such a description of the glass forming ability of multi-component alloys has heretofore never been proposed or discussed in any prior art. Accordingly, such a precise and quantitative description of the “inventive” composition region for formation for bulk metallic formation has never before been possible.
For the purpose of comparison,
The mechanical properties of the inventive alloys were investigated across the entire compositional range disclosed in this disclosure. The mechanical properties of interest are the yield strength, σy, which is the measure of the material's ability to resist non-elastic yielding, and the notch toughness, KQ, which is the measure of the material's ability to resist fracture in the presence of blunt notch. Specifically, the yield strength is the stress at which the material yields plastically, and notch toughness is a measure of the work required to propagate a crack originating from a blunt notch. Another property of interest is the bending ductility of the material, εp, which is the plastic strain attained by bending around a fixed bent radius. The bending ductility is a measure of the material's ability to resist fracture in bending in the absence of a notch or a pre-crack. To a large extent, these three properties determine the material mechanical performance under stress. A high σy ensures that the material will be strong and hard; a high KQ ensures that the material will be tough in the presence of relatively large defects, and a high εp ensures that the material will be ductile in the absence of large defects. The plastic zone radius, rp, defined as (1/π)(KQ/σy)2, is a measure of the critical flaw size at which catastrophic fracture is promoted. Essentially, the plastic zone radius determines the sensitivity of the material to flaws; a high rp designates a low sensitivity of the material to flaws.
The compressive strength, notch toughness, and bending ductility of inventive alloys Ni77.5−xCrxNb3P16.5B3, where x is between 4 and 13, were investigated. The compressive strength is found to increase monotonically with increasing Cr content (Table 7 and
The higher notch toughness and larger plastic zone radius of the alloys with low Cr atomic fractions is reflected in their fracture surface morphology. As shown in
The compressive strength, notch toughness, and bending ductility of inventive alloys Ni69Cr8.5Nb3P19.5−xBx, where x is between 2 and 4.5, were investigated. The compressive strength is found to increase fairly monotonically with increasing B content (Table 8 and
The compressive strength, notch toughness, and bending ductility of inventive alloys Ni69Cr11.5−xNbxP16.5B3, where x is between 2 and 4, were investigated. The compressive strength is found to increase fairly monotonically with increasing Nb content (Table 9 and
The compressive strength, notch toughness, and bending ductility of inventive alloys (Ni0.8541Cr0.1085Nb0.0374)100-x(P0.8376B0.1624)x, where x is between 18.7 and 20.7, were investigated. The compressive strength is found to decrease slightly for the intermediate x of 19.7% (Table 10 and
The density, shear, bulk, and Young's moduli, and Poisson's ratio of inventive alloys Ni77.5−xCrxNb3P16.5B3, where x is between 5 and 13, were measured (Table 11). The Poisson's ratio is plotted against the Cr content (
The density, shear, bulk, and Young's moduli, and Poisson's ratio of inventive alloys Ni69Cr8.5Nb3P19.5−xBx, where x is between 2 and 4.5, were measured (Table 12). The Poisson's ratio is plotted against the B content (
The density, shear, bulk, and Young's moduli, and Poisson's ratio of inventive alloys Ni69Cr11.5−xNbxP16.5B3, where x is between 2 and 4, were measured (Table 13). The Poisson's ratio is plotted against the Nb content (
The density, shear, bulk, and Young's moduli, and Poisson's ratio of inventive alloys (Ni0.8541Cr0.1085Nb0.0374)100-x(P0.8376B0.1624)x, where x is between 18.7 and 20.7, were measured (Table 14). The Poisson's ratio is plotted against the metalloid content (
In other embodiments, the present disclosure is also directed to Ni—Cr—Nb—P—B systems that further contain minority additions of Si. Specifically, substitution of up to 2 atomic percent P with Si in the inventive alloys is found to retain significant glass forming ability. As such, the Ni-based inventive alloys in this embodiment contain Cr in the range of 4 to 14 atomic percent, Nb in the range of 1.8 to 4.3 atomic percent, P in the range of 13.5 to 17.5 atomic percent, and B in the range of 2.3 to 3.9 atomic percent, and are capable of forming an amorphous phase in sections at least 3 mm thick, and up to 10 mm or greater. Preferably, the atomic percent of B in the alloys of the present disclosure is between about 2 and 4, and the combined fraction of P, B, and Si is between about 19 and 20 atomic percent. Also, the atomic percent of Cr is preferably between 7 and 10 and of Nb between 2.5 and 4.
Exemplary embodiments demonstrate that substitutions of up to about 2 atomic percent P with Si in the Ni68.5Cr9Nb3P16.5B3 system does not drastically degrade bulk metallic glass formation (Table 15 below, and
In a slightly modified composition, minority addition of Si was found to actually improve metallic glass formation (Table 16 below).
Specifically, it was discovered that the glass-forming ability is to a large extent retained or, in some cases, slightly improved by substituting up to about 1 percent of P with Si. calorimetry scans to determine the effects of Si concentration on the glass transition, crystallization, solidus, and liquidus temperatures were performed (
Minority addition of Si as a replacement for P is also found to have surprisingly dramatic effects on the mechanical properties. The compressive strength, notch toughness, and bending ductility of inventive alloys Ni68.5Cr9Nb3P16.5−xB3Six, where x is between 0 and 1.5, were investigated. The compressive strength of the Si bearing alloys is shown to increase with increasing Si content (Table 17 and
The compressive strength and notch toughness were also investigated for inventive alloys Ni77.5−xCrxNb3P16B3Si0.5, where x is between 7 and 10 (
The density, shear, bulk, and Young's moduli, and Poisson's ratio of inventive alloys Ni68.5Cr9Nb3P16.5−xB3Six, where x is between 0 and 1.5, were measured (Table 19). The Poisson's ratio is plotted against the Si content (
Although the above results provide detailed studies of the effect of Si on the GFA of the inventive alloys, in yet another embodiment up to 1.5 atomic percent of Nb in the inventive alloys can be substituted by Ta, V, or combinations thereof, while retaining bulk glass formation in rods of at least 3 mm in diameter. Exemplary embodiments of alloys containing additions of Si and Ta are presented in Table 20 below, and are shown to be able to form amorphous rods up to 6 mm in diameter. Also, up to 2 atomic percent of the Cr or up to 2 atomic percent of the Ni in the inventive alloys can be optionally substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, or combinations thereof.
The effect of Mo addition on the glass forming ability was examined for the compositions listed in Table 21, below.
Finally, despite the above, it will be understood that standard impurities related to the manufacturing limitations of some materials can be tolerated in concentrations of up to 1 wt. % without impacting the properties of the inventive alloys.
The corrosion resistances of exemplary amorphous alloys Ni69Cr8.5Nb3P16.5B3 and Ni68.6Cr8.7Nb3P16B3.2Si0.5 were evaluated by immersion tests in 6M HCl, and were compared against highly corrosion-resistant stainless steels. The plot of the corrosion depth vs. time for the three alloys is presented in
A preferred method for producing the inventive alloys involves inductive melting of the appropriate amounts of elemental constituents in a quartz tube under inert atmosphere. The purity levels of the constituent elements were as follows: Ni 99.995%, Cr 99.996%, Nb 99.95%, Ta 99.95%, Si 99.9999%, P 99.9999%, and B 99.5%. A preferred method for producing glassy rods from the alloy ingots involves re-melting the ingots in quartz tubes of 0.5-mm thick walls in a furnace at 1100° C. or higher, and preferably between 1150 and 1250° C., under high purity argon and rapidly quenching in a room-temperature water bath. In general, amorphous articles from the alloy of the present disclosure can be produced by (1) re-melting the alloy ingots in quartz tubes of 0.5-mm thick walls, holding the melt at a temperature of about 1100° C. or higher, and preferably between 1150 and 1250° C., under inert atmosphere, and rapidly quenching in a liquid bath; (2) re-melting the alloy ingots, holding the melt at a temperature of about 1100° C. or higher, and preferably between 1150 and 1250° C., under inert atmosphere, and injecting or pouring the molten alloy into a metal mold, preferably made of copper, brass, or steel. Optionally, prior to producing an amorphous article, the alloyed ingots can be fluxed with dehydrated boron oxide or any other reducing agent by re-melting the ingots in a quartz tube under inert atmosphere, bringing the alloy melt in contact with the molten reducing agent and allowing the two melts to interact for about 1000 s at a temperature of about 1100° C. or higher, and subsequently water quenching.
The glass-forming ability of each inventive alloy was assessed by determining the maximum rod diameter in which the amorphous phase can be formed when processed by the preferred method described above. X-ray diffraction with Cu-Kα radiation was performed to verify the amorphous structure of the inventive alloys. Images of fully amorphous rods made from exemplary amorphous alloys of the present disclosure with diameters ranging from 3 to 10 mm are provided in
Exemplary alloy Ni68.6Cr8.7Nb3P16B3.2Si0.5 was found to exhibit particularly high glass-forming ability. It was not only able to form 10 mm amorphous rods when quenched in a quartz tube with 0.5 mm thick wall, but can also form 10 mm amorphous rods when quenched in a quartz tube with 1 mm thick wall. This suggests that the critical rod diameter assessed by quenching in quartz tubes with 0.5 mm thick walls should be between 11 and 12 mm. An X-ray diffractogram with Cu-Kα radiation verifying the amorphous structure of a 10-mm rod of exemplary amorphous alloy Ni68.6Cr8.7Nb3P16B3.2Si0.5 produced by quenching in a quartz tube with 1 mm thick wall is shown in
Differential scanning calorimetry at a scan rate of 20° C./min was performed to determine the glass-transition, crystallization, solidus, and liquidus temperatures of exemplary amorphous alloys.
The shear and longitudinal wave speeds of exemplary amorphous alloys were measured ultrasonically on a cylindrical specimen 3 mm in diameter and about 3 mm in length using a pulse-echo overlap set-up with 25 MHz piezoelectric transducers. Densities were measured by the Archimedes method, as given in the American Society for Testing and Materials standard C693-93.
Compression testing of exemplary amorphous alloys was performed on cylindrical specimens 3 mm in diameter and 6 mm in length by applying a monotonically increasing load at constant cross-head speed of 0.001 mm/s using a screw-driven testing frame. The strain was measured using a linear variable differential transformer. The compressive yield strength was estimated using the 0.2% proof stress criterion.
The notch toughness of exemplary amorphous alloys was performed on 3-mm diameter rods. The rods were notched using a wire saw with a root radius of between 0.10 and 0.13 μm to a depth of approximately half the rod diameter. The notched specimens were placed on a 3-point bending fixture with span distance of 12.7 mm and carefully aligned with the notched side facing downward. The critical fracture load was measured by applying a monotonically increasing load at constant cross-head speed of 0.001 mm/s using a screw-driven testing frame. At least three tests were performed, and the variance between tests is included in the notch toughness plots. The stress intensity factor for the geometrical configuration employed here was evaluated using the analysis by Murakimi (Y. Murakami, Stress Intensity Factors Handbook, Vol. 2, Oxford: Pergamon Press, p. 666 (1987)). The fracture surface morphology of the inventive alloys is investigated using scanning electron microscopy.
The ability of rods made of exemplary amorphous alloys to bend plastically around a fixed bent radius was evaluated. Rods of various diameters were bent plastically around 6.3 mm bend diameter. The rod diameter at which a permanent 30° bent angle could be achieved was deemed as the “critical bending diameter”, dcr. The “bending ductility” εp, representing the plastic strain attainable in bending, was estimated by dividing dcr by 6.3 mm.
The hardness of exemplary amorphous alloy Ni68.6Cr8.7Nb3P16B3.2Si0.5 was measured using a Vickers microhardness tester. Six tests were performed where micro-indentions were inserted on the flat and polished cross section of a 3-mm rod using a load of 500 g and a duel time of 10 s. A micrograph showing a micro-indentation is presented in
The corrosion resistance of exemplary amorphous alloys was evaluated by immersion tests in hydrochloric acid (HCl), and was compared against highly corrosion-resistant stainless steels. A rod of inventive alloys Ni69Cr8.5Nb3P16.5B3 with initial diameter of 2.91 mm and length of 18.90 mm, a rod of inventive alloys Ni68.6Cr8.7Nb3P16B3.2Si0.5 with initial diameter of 2.90 mm and length of 20.34 mm, a rod of stainless steel 304 (dual-certified Type 304/304L stainless steel, ASTM A276 and ASTM A479, ‘cold rolled’ or ‘mill finish’ (unpolished)) with initial diameter of 3.15 mm and length of 16.11 mm, and a rod of stainless steel 316 (Super-Corrosion-Resistant Stainless Steel (Type 316), ASTM A276 and ASTM A479, ‘cold rolled’ or ‘mill finish’ (unpolished)) with initial diameter of 3.15 mm and length of 17.03 mm were immersed in a bath of 6M HCl at room temperature. The stainless steel rods were immersed for about 475 hours, the inventive alloy Ni69Cr8.5Nb3P16.5B3 rod was immersed for 2200 hours and Ni68.6Cr8.7Nb3P16B3.2Si0.5 for 373 hours. The corrosion depth at various stages during the immersion was estimated by measuring the mass change with an accuracy of ±0.01 mg. Corrosion rates were estimated assuming linear kinetics.
A database listing thermophysical and mechanical properties for exemplary amorphous alloy Ni68.6Cr8.7Nb3P16B3.2Si0.5 (Example 42) has been generated. The differential calorimetry scan for this alloy is presented in
Those skilled in the art will appreciate that the foregoing examples and descriptions of various preferred embodiments of the present disclosure are merely illustrative of the disclosure as a whole, and that variations in the steps and various components of the present disclosure may be made within the spirit and scope of the disclosure. For example, it will be clear to one skilled in the art that including minor additions or impurities to the compositions of the current disclosure would not impact the properties of those compositions, nor render them unsuitable for their intended purpose. Accordingly, the present disclosure is not limited to the specific embodiments described herein but, rather, is defined by the scope of the appended claims.
The present application is a continuation of U.S. patent application Ser. No. 13/592,095, filed Aug. 22, 2012, now U.S. Pat. No. 9,085,814, which claims priority to U.S. Provisional Application No. 61/526,153, filed Aug. 22, 2011, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61526153 | Aug 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13592095 | Aug 2012 | US |
| Child | 14797878 | US |
