Glassy Alloy Rods Research Articles

Formation and mechanical properties of Cu–Hf–Al bulk glassy alloys with a large supercooled liquid region of over 90 K

New Cu-based bulk glassy alloys with large supercooled liquid regions and high mechanical strength were formed in Cu–Hf–Al ternary systems. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at.% Hf at 2.5% Al, 37.5–50% Hf at 5% Al, and 45% Hf at 7.5% Al. The largest supercooled liquid region ΔTx(= Tx – Tg) was 91 K for Cu50Hf45Al5 alloy, and the highest reduced glass-transition temperature was 0.63 for Cu50Hf42.5Al7.5 and Cu52.5Hf40Al7.5 alloys. The alloys with large ΔTx values above 50 K were formed into bulk glassy rods with diameters up to 3 mm by copper mold casting, and the glassy alloy rods exhibited high compressive fracture strength of 2260 to 2370 MPa and Young's modulus of 121 to 128 GPa combined with elastic elongation of 1.9% to 2.0% and plastic elongation of 0.2% to 0.6%. No bulk glassy alloys were formed in the Cu–Hf binary system by copper mold casting, and, hence, the addition of 2.5% to 7.5% Al to Cu–Hf alloys was very effective for increasing glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of a unique glassy structure in special multicomponent alloys with the three component rules.

Mechanical properties of Fe-based bulk glassy alloys in Fe–B–Si–Nb and Fe–Ga–P–C–B–Si systems

Mechanical properties of cast Fe-based bulk glassy alloy rods with compositions of (Fe0.75B0.15Si0.1)96Nb4 and Fe77Ga3P9.5C4B4Si2.5 were examined by compression and Vickers hardness tests. The Young's modulus (E), yield strength (σy), fracture strength (σf), elastic strain (εe), fracture strain (εf), and Vickers hardness (Hv) were 175 GPa, 3165 MPa, 3250 MPa, 1.8%, 2.2%, and 1060, respectively, for the former alloy and 182 GPa, 2980 MPa, 3160 MPa, 1.9%, 2.2%, and 870, respectively, for the latter alloy. The εf /E and Hv/3E were 0.019–0.017 and 0.020–0.016, respectively, for the alloys, in agreement with the previous data for a number of bulk glassy alloys. The agreement suggests that these Fe-based bulk glassy alloys have an elastic–plastic deformation mode. The syntheses of high-strength Fe-based bulk glassy alloys with distinct compressive plastic strain and elastic–plastic deformation mode are encouraging for future development of Fe-based bulk glassy alloys as structural and soft magnetic materials.

Fabrication, Thermal Stability and Mechanical Properties of Porous Bulk Glassy Pd-Cu-Ni-P Alloys

Porous Pd42:5Cu30Ni7:5P20 glassy alloy rods with diameters of 7 and 10 mm and a length of about 20 mm were produced by water quenching the mixture of Pd42:5Cu30Ni7:5P20 liquid and solid salt phases at a volume fraction ratio of 7 to 9, followed by leaching treatment into water to eliminate the salt phase. The pores had a polyhedral shape with sizes of 125 to 250 mm. The densities were 3.3 and 4.2 Mg/m 3 and their pore fractions were evaluated as 65 and 55% for the 7 mm and 10 mm rods, respectively. The thickness of the cell walls was in the range of 50 to 250 mm. No crystalline phase was observed in the outer surface region as well as in the cell wall region. The glass transition temperature and crystallization temperature of the porous alloy rods were 578 and 679 K, respectively, in agreement with those of the pore-free alloy. Final rupture was not recognized for the porous alloys subjected to the uniaxial compressive test. The porous alloy exhibited lower Young’s modulus, lower yield strength, much higher absorption energy, being significantly different from those for the pore-free glassy alloy rod. The unique mechanical characteristics combined with high absorption energy ability indicate the possibility of future uses as a new type of structural and functional materials.

Formation, Thermal Stability, Mechanical Properties and Corrosion Resistance of Cu-Zr-Ti-Ni-Nb Bulk Glassy Alloys

Bulk glassy alloys exhibiting high strength and good corrosion resistance were formed in (Cu0:6Zr0:3Ti0:1)100� xyNiyNbx systems. The bulk glassy alloy rods with a diameter of 3 mm are formed in a wide composition range of 0 to 6 at%Ni and 0 to 6 at%Nb by copper mold casting. As the Nb content increases, the glass transition temperature (Tg) increases while the crystallization temperature (Tx) decreases, resulting in a decrease inTx ð¼ TxTgÞ from 60 K at 0 at%Nb to 36 K at 5 at%Nb. The high fracture strength (� c,f) exceeding 2000 MPa is obtained for the Cu-Zr-Ti-Ni-Nb alloys containing more than 3 at%Nb and their high strength alloys also exhibit distinct plastic elongation of 0.2 to 0.8%. The corrosion resistance of the Cu-Zr-Ti bulk glassy alloy is also significantly improved by the simultaneous addition of Ni and Nb and no loss in sample weight in 1 N HCl and 3%NaCl solutions is detected for the Cu-Zr-Ti-Ni-Nb alloys containing 5 at%Ni and 6 at%Nb or 2 at%Nb, respectively. The usefulness of the simultaneous addition of Ni and Nb on thec,f and corrosion loss in conjunction with high glass-forming ability seems to affect significant influence on the future development of bulk glassy alloys with special functional characteristics. prepared by arc melting the mixtures of pure metals in an argon atmosphere. The alloy compositions represent nominal atomic percentages. Cylindrical alloy rods with different diameters of 2 to 5 mm and a length of 70 mm were produced by a copper mold casting method. Alloy ribbons with a cross section of 0:03 � 1:2 mm 2 were produced by a melt spinning method. The glassy structure was examined by X-ray diffraction and transmission electron microscopy (TEM). Thermal stability associated with glass transition temperature and crystallization temperature was examined by differential scanning calorimetry (DSC) at a heating rate of 0.67 K/s. The melting and liquidus temperatures (Tm and Tl) were measured by differential thermal analysis (DTA) at a heating rate of 0.067 K/s. Mechanical properties were measured with an Instron testing machine. The gauge dimension was 2 mm in diameter and 4 mm in length and the strain rate was 5:0 � 10 � 4 s � 1 . Fracture surface was examined by scanning

Glass Transition Behavior and Mechanical Properties of Ni-Si-B-Based Glassy Alloys

The effect of transition metals Nb and Ta on the glass-forming ability of Ni75Si8B17 was examined. New Ni-Si-B-M (M = Nb, Ta) glassy alloys with high Ni contents above 70 at% were found to exhibit a glass transition before crystallization. The glass transition temperature (Tg) increases continuously with increasing Nb or Ta content. The supercooled liquid region (� Txð¼ TxTgÞ) and reduced glass transition temperature (Tg=Tl) are 30 K and 0.59, for (Ni0:75Si0:08B0:17)96Nb4 and 35 K and 0.61, for (Ni0:75Si0:08B0:17)96Ta4, respectively. These two glassy alloys exhibit high fracture strength and good bend ductility. The maximum fracture strength of the Ni-Si-B-Nb and Ni-Si-B-Ta alloys is 2510 and 2730 MPa, respectively. All the samples can be folded through an angle of 180 degrees without fracture. The use of the glassy-type (Ni0:75Si0:08B0:17)96Ta4 alloy enabled us to form a glassy alloy rod with a diameter of 0.5 mm by the copper mold casting method. The combination of the new alloy composition, high glass-forming ability and good mechanical properties of the Ni-based glassy alloys indicates that the new bulk glassy alloy may be used as a new type of engineering material.

Bulk Glassy Alloys with Low Liquidus Temperature in Pt-Cu-P System

Bulk glassy alloys with low values of liquidus temperature (T 1 ) and glass transition temperature (Tg) as well as high T g /T 1 were formed at Pt 60 Cu 20 P 20 . Glassy alloys in Pt 80-x Cu x P 20 system were formed over the whole composition range up to 35 at%Cu examined in the present study. The T g increases significantly with increasing Cu content, shows a maximum value of 522 K at 20%Cu and then decreases slightly with further increase in Cu content. On the other hand, the crystallization temperature (T x ) increases monotonously with increasing Cu content up to 25 at%Cu and then becomes saturated, leading to a monotonous increase in ΔT x (=T x -T g ) from 25 K at 0%Cu to 83 K at 35 at%Cu. All the ternary glassy alloys crystallize through a single-stage exothermic reaction, accompanied by the precipitation of mixed Pt 5 P 2 , Cu 3 P and unknown phases. The 20%Cu-containing alloy has the lowest T 1 of 854 K as well as the smallest temperature interval of 21 K between T 1 and melting temperature (T m ) and hence the highest T g /T 1 of 0.61 is obtained for the 20%Cu alloy. The high T g /T 1 as well as the low T 1 has enabled us to form bulk glassy alloy rods with diameters up to at least 12 mm by water quenching. The synthesis of the Pt-Cu-P glassy alloys with the low values of T g and T 1 and the large ΔT x is important for future development as precision materials for nano-technology which can be deformed through viscous flow.

Formation, Thermal Stability and Mechanical Properties in Zr-Al-Co Bulk Glassy Alloys

A Zr–Al–Co ternary alloy was investigated in order to clarify the glass-forming ability, thermal stability and mechanical properties. The Zr55Al20Co25 alloy was found to be fabricated in bulk glassy alloy rods with diameters up to at least 2.5 mm. The glassy alloy rod of 2.5 mm in diameter exhibits a large supercooled liquid region of 79 K, followed by a nearly single exothermic peak due to the precipitation of ZrCo+ZrAlCo+Zr6Al2Co phases. The glassy alloy rod exhibits Young’s modulus of 114 GPa, high compressive fracture strength of 1900 MPa and total fracture elongation of 1.7%. The finding of forming the bulk glassy alloy at the new ternary composition of Zr55Al20Co25 by the copper mold casting method is encouraging for future search of a new glassy alloy composition.

Thermal Stability and Soft Magnetic Properties of (Fe, Co)-(Nd, Dy)-B Glassy Alloys with High Boron Concentrations

Fe-based glassy alloys with high boron concentrations in (Fe, Co)–(Nd, Dy)–B system were found to exhibit a large supercooled liquid region (∆Tx) and good soft magnetic properties. The Fe62Co9.5Nd3Dy0.5B25 glassy alloy with ∆Tx of 56 K exhibits high saturation magnetization ( Is) of 1.41 T, low coercive force ( Hc) of 2.6 A/m and large permeability (µe) at 1 kHz of 12000. The Fe62Co9.5Nd3Dy0.5B25 glassy alloy rods were produced in the diameter range up to 0.75 mm by copper mold casting. The substitution of 2 at% elements TM (TM = Nb, Ta, Mo and W) for Fe and Co, remarkably increases the ∆Tx and Tg/Tl, leading to an increase in the glass-formation ability (GFA) for Fe60.3Co9.2Nd3Dy0.5B25TM2. The ∆Tx and Tg/Tl increase from 56 to 87 K and 0.56 to 0.57, respectively, and the glassy alloy rods were produced in the diameter range up to 1.2 mm. The saturation magnetization Is decreases slightly, while the coercive force Hc remains almost unchanged by the addition of 2 at% TM elements.

Bulk Glass Formation of Ti-Zr-Hf-Cu-M (M=Fe, Co, Ni) Alloys

The glass-forming ability of Ti–Zr–Hf–Cu–M (M=Fe, Co, Ni) alloys was examined by melt-spinning and copper mold casting methods. New Ti20Zr20Hf20Cu20Ni20 bulk glassy rod of 1.5 mm in diameter was formed by copper mold casting. The Tx and Tg of the glassy rod were 711 K and 658 K and Tg/Tm was 0.57. The bulk glassy alloy can be characterized by equal concentration of constituent elements without distinct host component. It is confirmed that more multicomponent glassy systems have a better glass-forming ability as compared with simpler alloy systems. The glassy alloy rod also exhibits good mechanical properties which are similar to those for ordinary glassy alloys. The finding of this alloy system may provide a new synthesis method of bulk glassy alloys.

Formation, Thermal Stability and Mechanical Properties of Cu-Zr-Al Bulk Glassy Alloys

New Cu-based bulk glassy alloys with large supercooled liquid region and high mechanical strength were found to be formed in Cu-Zr-Al ternary system. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at%Zr at 2.5 at%Al, 37.5%Zr to 47.5%Zr at 5%Al and 42.5%Zr at 7.5%Al. The largest ΔT x was 74 K for Cu 55 Zr 40 Al 5 and Cu 50 Zr 42.5 Al 7.5 alloys and the highest T g /T l was 0.62 for the former alloy. The alloys with large ΔT x values above 70 K were formed into a bulk glassy rod form with diameters up to 3 mm by copper mold casting and the glassy alloy rods exhibit high compressive strength of 1885 to 2210 MPa and Young's modulus of 102 to 115 GPa combined with elastic elongation of 1.60 to 1.95% and plastic elongation of 0 to 0.4%. The addition of 2.5 to 7.5°%Al to Cu-Zr alloys was very effective for the increase in glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of the unique glassy structure in special multi-component alloys with the three empirical component rules.

Fabrication of Bulk Glassy Hf<SUB>50</SUB>Cu<SUB>30</SUB>Ni<SUB>10</SUB>Al<SUB>10</SUB> Alloy by Copper Mold Casting

The glass-forming ability of the Hf50Cu30Ni10Al10 alloy was examined by melt-spinning and copper mold casting methods. A new Hf50Cu30Ni10Al10 bulk glassy rod of 3 mm in diameter was formed by copper mold casting. The crystallization temperature (Tx), glass transition temperature (Tg) and Tg⁄Tl of the glassy alloy rod were 780 K, 860 K and 0.61, respectively. The Hf50Cu30Ni10Al10 bulk glassy alloy exhibits density of 11.0×103 kg/m3, Vickers hardness of 590, Young’s modulus of 118 GPa and compressive fracture strength of 2420 MPa. The synthesis of the Hf-based bulk glassy alloy with high Tg⁄Tl, high fracture strength and high density is encouraging for future application of bulk glassy alloys.

New Glassy Zr-Al-Fe and Zr-Al-Co Alloys with a Large Supercooled Liquid Region

New Zr-Al-Co and Zr-Al-Fe ternary glassy alloys were found to exhibit a large supercooled liquid region above 50 K before crystal- lization. The largest value of the supercooled liquid region was 64 K for Zr 55Al20Co25 and 50 K for Zr70Al15Fe15. The highest value of the reduced glass transition temperature (Tg/Tl) was 0.61 for Zr55Al20Co25 and 0.60 for Zr70Al15Fe15. The use of the Zr55Al20Co25 alloy with the highest Tg/Tl has enabled us to form bulk glassy alloy rods with diameters up to 3 mm by copper mold casting. The Young's modulus, yield strength, compressive fracture strength, elastic elongation and fracture elongation of the Zr 55Al20Co25 glassy rod are 92 GPa, 2050 MPa, 2200 MPa, 2.1% and 0.9%, respectively. The distinct plastic elongation indicates that the Zr-based bulk glassy alloy has rather a good ductile nature. The synthesis of the high-strength bulk glassy alloy in the new ternary system is expected to gain a new application field as a new type of bulk glassy alloy. For the last decade, much attention has been paid to bulk glassy alloys because of the importance of scientific and engi- neering aspects. The motivation for the present global atten- tion to bulk glassy alloys has been attributed to the discoveries of new series of glassy alloys with a large supercooled liquid region before crystallization in Mg-Ln(lanthanide metal)- (Ni, Cu), 1) Ln-Al-(Ni, Cu) 2) and Zr-Al-(Ni, Cu) 3) systems. The high thermal stability of the supercooled liquid against crystallization has enabled us to form bulk glassy alloys by various casting processes. It has subsequently been reported that bulk glassy alloys are also formed in a number of alloy systems, i.e., other Zr-based systems of Zr-Ti-Be-(Ni, Cu) 4) and Zr-(Ti, Nb, Pd)-Al-(Ni, Cu), 5) and Ti-, 6) Hf-, 7) Fe-, 8) Pd-Cu-, 9) Co-, 10) Ni- 11) and Cu- 12) based systems. The low- est critical cooling rate for glass formation is 0.03 K/s for the Pd-Cu-Ni-P system. The maximum sample diameter is ap- proximately 80 mm for the Pd-based system 13) and 30 mm for the Zr-based system. 14) The Zr- and Pd-based bulk glassy al- loys have been used as practical materials of sporting goods and electrodes. 15-17) In the development history of the Zr- based bulk glassy alloys, their alloy components had been limited to two groups of Zr-Al-(Ni, Cu) including Ti, Nb, Ta or Pd and Zr-Ti-Be-(Ni, Cu). It is important to search for new Zr-based glassy alloys with the high thermal stability of supercooled liquid and to extend bulk glassy alloy systems. Very recently, we have found that a large supercooled liquid region above 50 K before crystallization is obtained for new glassy alloys in Zr-Al-Fe and Zr-Al-Co systems. The find- ing of the simple ternary glassy alloys is important because the extension of the ternary base system to more multicom- ponent systems is expected to form bulk glassy alloys with a larger supercooled liquid region and higher glass-forming ability. This paper presents the composition ranges in which glassy alloys with a larger supercooled liquid region before crystallization are formed in Zr-Al-Fe and Zr-Al-Co ternary systems. Further, thermal and mechanical properties of their glassy alloys are investigated. 2. Experimental Procedure

Formation and Soft Magnetic Properties of Co-Fe-Si-B-Nb Bulk Glassy Alloys

Soft ferromagnetic bulk glassy alloys in Co-Fe-Si-B base system were formed in the diameter range up to 1 mm at the composition of (Co 0.705 Fe 0.045 Si 0.1 B 0.15 ) 96 Nb 4 by copper mold casting. Since no bulk glass formation has been obtained in the Co-Fe-Si-B system, the addition of 4%Nb is very effective for the increase in the glass-forming ability. The effectiveness was interpreted by satisfaction of the three component rules for formation of bulk glassy alloys. The bulk glassy alloys exhibit the glass transition before crystallization. The glass transition temperature (T g ), the supercooled liquid region defined by the difference between Tg and crystallization temperature (T x ), ΔT x (= T x - T g ) and the reduced glass transition temperature (T g /T i ) are 823K, 37 K and 0.61, respectively. The bulk glassy alloys also exhibit soft magnetic properties with saturation magnetization (I s ) of about 0.60T and low coercive force (H c ) below 3A/m. The synthesis of the Co-based bulk glassy alloy rods with glass transition and good soft magnetic properties is important for future development as a new type of soft magnetic bulk material.

Formation and Soft Magnetic Properties of Fe-B-Si-Zr Bulk Glassy Alloys with High Saturation Magnetization above 1.5 T

A new Fe-based bulk glassy alloy with good soft magnetic properties and high saturation magnetization (I s ) above 1.5 T was formed at the composition of (Fe 0.75 B 0.15 Si 0.1 ) 99 Zr 1 . The addition of I at%Zr to Fe 75 B 15 Si 10 caused the appearance of glass transition (T g ) at 815 K, followed by a supercooled liquid region (ΔT x (= T x - T g )) of 52 K, in addition to a decrease of Curie temperature (T c ) from 714 to 688 K and an increase of crystallization temperature (T x ) from 845 to 868 K. The reduced glass transition temperature (T g /T l ) was measured as 0.59. The increase in the supercooled liquid region enabled us to form bulk glassy alloy rods in the diameter range up to 0.75 mm by the copper mold casting method. The T c , T g , ΔT x and crystallization peak behavior for the bulk glassy alloy rods are nearly the same as those for the corresponding ribbon sample. The bulk glassy alloy rods exhibit high I s of 1.53 T and low coercive force (H c ) of 2.8 A/m which are comparable to commercial Fe-based amorphous alloy ribbons. The good combination of the new Fe-based alloy composition, high glass-forming ability and good soft magnetic properties indicates that the new bulk glassy alloy may be used as a new type of soft magnetic material.

Soft Magnetic Bulk Glassy Fe-B-Si-Nb Alloys with High Saturation Magnetization above 1.5 T

New Fe-based bulk glassy alloys were synthesized in the (Fe 0.75 B 0.15 Si 0.10 ) 100-x Nb x system by copper mould casting. The maximum diameter of the bulk glassy alloy rod was 0.5 mm at I at%Nb, 1.0 mm at 2 at%Nb and 1.5 mm at 4 at%Nb. No glass transition is observed at 0 at % Nb, but the addition of Nb causes the appearance of glass transition before crystallization. The glass transition temperature (Tg) and crystallization temperature (T x ) of the bulk glassy rods were 815 K and 858 K, respectively, for the 1 at%Nb alloy, and 835 K and 885 K, respectively, for the 4 at%Nb alloy. The reduced glass transition temperature (T g /T l ) defined by the ratio of Tg to the liquidus temperature (T l ) was measured as 0.56 at I at%Nb, 0.57 at 2 at%Nb and 0.61 at 4 at%Nb. There is a tendency for T g , ΔT x (= T x - T g ) and T g /T l to increase with increasing Nb content. The effect of Nb addition can be interpreted in the framework of the three component rules for the formation of bulk glassy alloys and the stabilization of supercooled liquid. The Fe-B-Si alloy satisfies the three component rules by the addition of Nb. The bulk glassy alloy rods exhibited good soft magnetic properties, i.e., high saturation magnetization (I s ) of 1.47 to 1.51 T, low coercive force (H c ) of 2.9 to 3.7 A/m and Curie temperature of 593 to 684 K. The high I s and low H c , as well as the formation of bulk glassy alloys in the simple alloy system are promising as a new type of soft magnetic bulk alloy.

Bulk Glassy Fe-Ga-P-C-B Alloys with High Saturation Magnetization and Good Soft Magnetic Properties Synthesized by Fluxing Treatment and Copper Mold Casting

The effect of fluxing treatment on the glass-forming ability for the Fe75Ga5P12C4B4 glassy alloy was investigated. The fluxing treatment was found to be effective for the elimination of heterogeneous nucleation sites. The glass transition temperature (Tg), crystallization temperature (Tx), supercooled liquid region (ΔTx) and reduced glass transition temperature (Tg⁄Tm) are all increased by fluxing treatment. The Tg, Tx, ΔTx and Tg⁄Tm values for Fe75Ga5P12C4B4 glassy alloy are 731 K, 768 K, 37 K and 0.610 respectively before fluxing treatment, increase to 749 K, 805 K, 56 K and 0.625 respectively after fluxing treatment. Bulk glassy Fe75Ga5P12C4B4 alloy rods with high saturated magnetization (Is) of 1.27 T and good soft magnetic properties of 1.6 A/m for coercive force (Hc) were prepared with diameters range up to 2.5 mm by the copper mold casting method of fluxed alloy melt. The glass synthesis consists of preparing the alloy ingot by induction melting, thermal cycling and purifying the melt in B2O3 flux inside a silica tube and then casting the purified alloy into a copper mold. The size of 2.5 mm in diameter of the rod is not an upper limit.

High-Strength Cu-Based Bulk Glassy Alloys in Cu-Zr-Ti-Be System

New Cu-based bulk glassy alloys with high glass-forming ability and good mechanical properties were formed in Cu-Zr-Ti-Be system. The glass transition temperature (T g ), supercooled liquid region defined by the difference between crystallization temperature (T x ) and Tg, ΔT x (=T x -T g ) and reduced glass transition temperature (T g /T l ) are 728 K, 50 K and 0.64, respectively, for the (Cu 0.6 Zr 0.3 Ti 0.1 ) 92.5 Be 7.5 and 720 K, 42 K and 0.64, respectively, for the Cu 54 Zr 27 Ti 9 Be 10 alloy. The use of the 7.5%Be and 10%Be alloys has enabled us to form glassy alloy rods with diameters up to 5 mm. The bulk glassy 10%Be alloy exhibits high tensile fracture strength of 2450 MPa and Vickers hardness of 710, in combination with Young's modulus of 146 GPa, compressive fracture strength of 2500MPa and compressive elongation of 3.5%. The tensile strength level is the highest among all bulk metallic glasses and hence the new Cu-based bulk glassy alloys have significant importance in basic science and engineering aspects.