Ni-based Bulk Research Articles

Deformation behavior of Ni-based bulk metallic glass synthesized by spark plasma sintering

Abstract We report the deformation behavior of the Ni-based bulk metallic glass (BMG) by spark plasma sintering of amorphous powders, which have been prepared by a gas atomization. By spark plasma sintering of amorphous powders in the supercooled liquid region, a fully Ni-based BMG was successfully synthesized. Full densification was achieved by the viscous flow of the amorphous powders in the supercooled liquid region during consolidation process. The strength of about 2.4 GPa was obtained in the consolidated BMG, which is comparable to that of the as-cast BMG (2.6 GPa). The consolidated Ni-based BMG shows similar super-plastic behavior to the as-cast BMG, indicating that possibility of deformation in the supercooled liquid region.

EXPERIMENTAL OBSERVATIONS OF THE FAILURE MECHANISMS IN A BULK METALLIC GLASS COMPOSITE

AbstractThe deformation and damage evolution behavior of a Ni-based bulk metallic glass composite reinforced with elongated brass phase is studied under cylindrical indentation. The estimated fracture toughness values based on the energy dissipation and the in-situ observation during the loading reveal the details of the damage evolution and toughening mechanisms in this composite system. The results indicate that the enhanced toughness of the BMG composite is plausibly an outcome of crack bridging mechanisms by the ductile brass phase, rather than a diffused array of nucleated shear bands in the hard BMG and arrest by the ductile reinforcing phase.

Formation of a Ni-Based Glassy Alloy in Centimeter Scale

The effect of B addition on the glass formation in the Ni 60 Pd 20 P 20 alloy has been investigated. The composition containing 3 at % of B was found to show a drastically improved glass-forming ability. A glassy Ni 60 Pd 20 P 1 7 B 3 alloy rod was prepared with a diameter of 12 mm by a water quenching technique. It is so far the first time to prepare a Ni-based bulk glassy alloy with a diameter over 1 cm. The glassy Ni 60 Pd 20 P 17 B 3 alloy also exhibits good mechanical properties, such as high strength of 2060 MPa and a large plastic strain of 0.08 under a compressive load.

A topological approach to design Ni-based bulk metallic glasses with high corrosion resistance

The structural model for metallic glasses and the topological instability criterion for multicomponent alloy systems have been combined to formulate a design protocol for bulk metallic glasses (BMGs). New Ni-Nb-Zr bulk metallic glasses with high corrosion resistance have been discovered. The experimental results in literature also support the use of this approach as a practically efficient method to select bulk metallic glass-forming compositions.

Formation and Thermal Stability of Ni-Based Bulk Metallic Glasses in Ni-Zr-Nb-Al System

An Al element was selected as an alloying metal to improve the glass-forming ability (GFA) of Ni-Zr-Nb alloys. The thermal stability and glass-forming ability of Ni-Zr-Nb-Al alloys were investigated. It was found that the partial substitution of Nb by Al led to significant shift of the onset crystallization temperature T x and the liquidus temperature T l , while the glass transition temperature Tg was less composition sensitive. The supercooled liquid region, AT, (= T x - T g ), the reduced glass transition temperature (T g /T l ) and y = T x /(T g + T l ) increased with increasing Al content up to 5 at%. The best GFA was found at Ni 60 Zr 20 Nb 15 Al 5 with a critical diameter of 3 mm. The characteristic parameters are: ΔT x = 54 K, T g /T l = 0.615 and y = 0.405. The maximum values of ΔT x and Tg/T, were 72 K and 0.617, respectively, at Ni 60 Zr 25 Nb 10 Al 5 . The compression tests showed that the Ni 60 Zr 20 Nb 15 Al 5 BMG possessed high fracture strength of 2900 MPa, Young's modul of 152 GPa, and plastic elongation of 2.5% at room temperature.

Consolidation behavior of Cu- and Ni-based bulk metallic glass composites

The Cu- and Ni-based bulk metallic glass matrix composites were fabricated by spark plasma sintering of a mixture of gas-atomized metallic glass powders and ductile brass powders. The brass powders added for the enhancement of plasticity are well distributed in the matrix after consolidation. The matrix of the composite materials remains as a fully amorphous phase after consolidation process. With increasing the brass content, the level of plasticity strain increased, although the level of strength decreased. The successful consolidation of metallic glass matrix composite with high density was attributed to viscous flow in the supercooled liquid state during spark plasma sintering.

Fabrication of Binary Ni‐Nb Bulk Metallic Glass with High Strength and Compressive Plasticity

Off‐eutectic Ni61.5Nb38.5 alloy, exhibiting the highest glass‐forming ability in the binary Ni‐Nb system, can be cast into the 1.5mm‐diameter fully amorphous rods by using copper mold injection casting method. Room temperature uniaxial compression tests yield for the high fracture strength and compressive plastic strain values of about 3.4GPa and 2%, respectively. The successful fabrication of the bulk metallic glassy samples in the binary Ni‐Nb alloy is of great interest to prepare large dimension Ni‐based bulk metallic glasses as structural materials.

A study of glass-formation, formation of the supercooled liquid and devitrification behavior of Ni-based bulk glass-forming alloys

Glass-formation and devitrification of the glassy phase in the Ni–Nb–Zr–Ti and Ni–Nb–Zr–Ti–NM (NM, noble metals) system alloys exhibiting the supercooled liquid on heating were investigated. The crystallized structure and kinetics of devitrification of Ni–Nb–Zr–Ti–Pd glassy alloy are studied in detail. The formation of the glassy single phase has been proven using high-resolution transmission electron microscopy (TEM). The addition of Zr and Pd increases the supercooled liquid region of the Ni 60Nb 25Ti 15 (numbers indicate at.%) alloy from 44 K to about 50 K. The cP2 TiNi phase was found to form during the first exothermic phase transformation in all studied alloys. The addition of Zr to Ni–Nb–Ti alloy prevents formation of oP8 Ni 3Nb phase observed in the Ni 60Nb 25Ti 15 alloy and initiates formation of the primary Ni 10Zr 7 phase while the additions of both NM and Zr effectively refine cP2 TiNi particles size. Definite fractions of rhombohedral R and hR14 Ni 4Ti 3 phases were also observed in NM-bearing alloys. Significantly lower growth rates of the devitrification products in the NM-bearing alloys compared to the Ni–Nb–Ti one may be the reason for the improvement of glass-forming ability (GFA).

Stability of Ni-based bulk metallic glasses

Several ternary (NixNbySnz) refractory alloy glasses (RAGs) were studied at elevated temperatures in order to assess the stability of the amorphous state, i.e. devitrification, and to identify subsequent phase transformations in these materials. differential scanning calorimetry (DSC) experiments indicated a complex phase transformation sequence with several distinct crystallization and melting events being recorded above the glass transition temperature, Tg. Below Tg the RAG samples were studied with an in situ environmental X-ray furnace facility, which allowed step-wise isothermal ramping experiments commencing at a temperature below the reduced temperature of T/Tg≈0.80. Distinct crystalline phases were observed when T/Tg≈0.84 for ternary RAG alloys, while similar experiments on Zr-based Vit 106 glass alloys did not reveal any apparent phase separation until T/Tg≈0.96. The phase separation kinetics followed an Arrhenius type of relationship with Ni3Sn, and Nb2O5 being the principle crystalline precipitates.

Influence of thermal conductivity on the glass-forming ability of Ni-based and Cu-based alloys

In the present letter we compare the thermal conductivities of Cu- and Ni-based alloys in relation with their cooling rates and glass-forming abilities. The cooling rates obtained for Cu- and Ni-based bulk glass-forming alloys are found to scale with the thermal conductivities of the base elements. Relatively low thermal conductivity of Ni-based alloy compared to the Cu-based one explains its lower glass-forming ability. The results also indicate that the thermal conductivity of the molten alloy should be also used as an indicator of the glass-forming ability among the other factors.

Ni-based bulk glassy alloys with superhigh strength of 3800MPa in Ni–Fe–B–Si–Nb system

The effects of replacement of Ni by Fe on the glass-forming ability (GFA) and mechanical properties of Ni–B–Si–Nb glassy alloys were examined. The substitution of Fe for Ni caused increases of GFA and mechanical properties. Ni-based bulk glassy alloys (BGAs) with diameters up to 3mm were formed in a [(Ni1−xFex)0.75B0.2Si0.05]96Nb4 alloy system. The BGAs exhibit a superhigh fracture strength of 3680–3840MPa and Young’s modulus of 172–186GPa, which are the highest values for Ni-based BGAs. The improvement of GFA and fracture strength is interpreted to result from the enhanced atomic bonding nature among the constituent elements by adding Fe.

Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System

We review our recent results of the formation, fundamental properties, workability and applications of late transition metal base bulk glassy alloys which have been developed after the first synthesis of Fe-based bulk glassy alloys by the copper mold casting method in 1995. The late metal transition base bulk glassy alloys were obtained in Fe–(Al,Ga)–(P,C,B,Si), Fe–(Cr,Mo)–(C,B), Fe–(Zr,Hf,Nb,Ta)–B, Fe–Ln–B(Ln=lanthanide metal), Fe–B–Si–Nb and Fe–Nd–Al for Fe-based alloys, Co–(Ta,Mo)–B and Co–B–Si–Nb for Co-based alloys, Ni–Nb–(Ti,Zr)–(Co,Ni) for Ni-based alloys, and Cu–Ti–(Zr,Hf), Cu–Al–(Zr,Hf), Cu–Ti–(Zr,Hf)–(Ni,Co) and Cu–Al–(Zr,Hf)–(Ag,Pd) for Cu-based alloys. These bulk glassy alloys exhibit useful engineering properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based bulk glassy alloys have good soft magnetic properties which cannot be obtained for conventional amorphous and crystalline type magnetic alloys. The Fe- and Ni-based bulk glassy alloys have already been used in some application fields. These late transition metal base bulk glassy alloys are promising as new metallic engineering materials.

Synthesis and Thermal Stability of New Ni-Based Bulk Glassy Alloy with Excellent Mechanical Properties

The thermal stability, glass-forming ability (GFA) and mechanical properties of the Ni-Ta-Ti and Ni-Ta-Ti-Zr glassy alloys have been investigated. As the Ti content increases, the supercooled liquid region ΔT x (= T x - T g ) and reduced glass transition temperature (T g /T l ) of Ni 60 Ta 40-x Ti x glassy alloys increase, showing maximum values of 63 K at 20%Ti and 0.59 at 25 at%Ti, respectively, and then gradually decrease. The addition of Zr to Ni-Ta-Ti alloys is effective for the increase in ΔT x and T g /T l . The maximum ΔT x and T g /T l values of 73 K and 0.60, respectively, are obtained for Ni 60 Ta 15 Ti 20 Zr 5 alloy. The Ni-Ta-Ti-Zr glassy alloys were formed in the rod form with diameters of over 1.0mm by copper mold casting. The Ni-Ta-Ti-Zr bulk glassy alloys exhibit excellent mechanical properties, i.e., the compressive fracture strength (σ c,f ) of 3180-3220 MPa and the compressive plastic elongation (e c,p ) of 0.2-0.4%.

Synthesis of Ni-Based Bulk Metallic Glasses Composites by Spark Plasma Sintering

Synthesis of Ni-Based Bulk Metallic Glasses Composites by Spark Plasma Sintering

Ni-based bulk glassy alloys with large supercooled liquid region exceeding 90 K

The formations of glassy and supercooled liquid phases in Ni–Nb–Zr–Ti, Ni–Nb–Zr–Ti–Pt and Ni–Nb–Zr–Ti–Pt–Cu alloys were studied by using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. It is found that the additions of Pt and Cu increase the supercooled liquid region of Ni–Nb–Zr–Ti alloy from 42 to 89 and 91 K, respectively. The increase in the supercooled liquid region is achieved mostly because T x rises more intensively than T g with Pt content. Quite low liquidus temperature of about 1300 K and high T g value of about 850 K obtained for the studied alloys lead to a high T g/ T l ratio which reaches 0.65 and favors the glass-forming ability. Nucleation and growth of Ni 4Ti 3 and Ni 10(Zr,Ti) 7 ss phases takes place from the supercooled liquid in Ni 60Nb 10Zr 15Ti 15 and Ni 52.5Nb 10Zr 15Ti 15Pt 7.5 alloys.

Formation of Refractory Ni-Based Bulk Metallic Glass in the Ni-Nb-Sn and Ni-Nb-Sn-X (X= Fe, B, Cu, Ta) Alloy Systems

Formation of Refractory Ni-Based Bulk Metallic Glass in the Ni-Nb-Sn and Ni-Nb-Sn-X (X= Fe, B, Cu, Ta) Alloy Systems

A development of Ni-based alloys with enhanced plasticity

Enhancement of plasticity in Ni-based injection cast bulk metallic glasses (BMGs) and metallic glass matrix composites (MGMCs) has been investigated. The injection-cast Ni 59Zr 16Ti 13Si 3Sn 2Nb 7 BMG showed a significantly improved plastic region to failure of 6.5%, as compared to that of the injection-cast Ni 59Zr 20Ti 16Si 2Sn 3 BMG of 2%. The Ni 59Zr 20Ti 16Si 2Sn 3 MGMC containing brass-fibers shows macroscopic plasticity after yielding, and the level of plastic strain increased to around 2% with increasing brass content up to 40 vol.%, while monolithic warm-extruded Ni 59Zr 20Ti 16Si 2Sn 3 BMG show no plastic deformation region. Present study shows that the plasticity of BMG can be improved by selecting proper BMG alloy composition or by introducing ductile reinforcing phase in the BMG matrix.

Nanocrystallization kinetics of Ni-based bulk amorphous alloy

The bulk amorphous alloy Ni 45Ti 23Zr 15Si 5Pd 12 has been prepared by copper mold casting. The crystallization kinetics of the alloy has been investigated using differential scanning calorimetry by means of continuous heating and isothermal annealing, and the products of crystallization have been analyzed by transmission electron microscopy and X-ray diffraction. The isothermal activation energy obtained from Arrhenius equation increases in the process of crystallization transformation. The details of nucleation and growth during the isothermal crystallization are expatiated in terms of local Avrami exponent and local activation energy. Meanwhile, the origins of nanocrystal formation during the annealing process have also been discussed.

Formation and properties of new Ni-based amorphous alloys with critical casting thickness up to 5 mm

New Ni-based bulk metallic glasses were synthesized in Ni x Cu a − x Ti y Zr b − y Al 10 ( a∼ b∼45 at.%) system, based on a ternary alloy, Ni 45Ti 20Zr 35. The additions of Al and Cu greatly increase the glass-forming ability (GFA). The best GFA is located around Ni 40Cu 5Ti 16.5Zr 28.5Al 10, from which fully amorphous samples of up to 5 mm thickness were successfully fabricated by an injection mold casting method. These alloys exhibit high glass-transition temperatures T g∼760 to 780 K, and relatively wide undercooled-liquid regions Δ T (defined by the difference between T g and the first crystallization temperature T x1 upon heating) ∼40–50 K. Mechanical tests on these alloys show quite high Vicker's Hardness ∼ 780 to 862 kg/mm 2, Young's modulus ∼ 111 to 134 GPa, shear modulus ∼ 40 to 50 GPa and high fracture strength ∼ 2.3 to 2.4 GPa. The effect of small Si-addition and a discrepancy between GFA and Δ T are also reported. The exceptional GFA and the all-metallic compositions give these new alloys excellent promise for both scientific and engineering applications.

A development of Ni-based alloys with enhanced plasticity

Enhancement of plasticity in Ni-based injection cast bulk metallic glasses (BMGs) and metallic glass matrix composites (MGMCs) has been investigated. The injection-cast Ni59Zr16Ti13Si3Sn2Nb7 BMG showed a significantly improved plastic region to failure of 6.5%, as compared to that of the injection-cast Ni59Zr20Ti16Si2Sn3 BMG of 2%. The Ni59Zr20Ti16Si2Sn3 MGMC containing brass-fibers shows macroscopic plasticity after yielding, and the level of plastic strain increased to around 2% with increasing brass content up to 40 vol.%, while monolithic warm-extruded Ni59Zr20Ti16Si2Sn3 BMG show no plastic deformation region. Present study shows that the plasticity of BMG can be improved by selecting proper BMG alloy composition or by introducing ductile reinforcing phase in the BMG matrix.