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Ti40Ni40Cu20 amorphous matrix composite plate specimens were fabricated by the levitation suspend melting-water cooled Cu mold process. The specimens were pre-compressed at different degrees with a universal testing machine and then annealed at 150 °C for 30 min. The effects of pre-deformation annealing processes on the microstructure and mechanical properties of Ti40Ni40Cu20 alloy system were studied by a metallographic microscope, X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show the martensitic phase transformation that of the austenite phase under external force occurs. The phase transition induced by the deformation coupled with the annealing release of residual thermal stress plays a role in enhancing both strength and toughness of the amorphous matrix composite. Both martensite phases and austenite phases are increased with the increase with the degrees of pre-deformation increasing, and martensite phases are increased faster. Thus, the yield strength of the composite increases, while the ductility declines. Therefore the controllable yield strength in the pre-compression stage for shaping can be realized.

Tapered Cu 50 Zr 42 Al 8 alloy with good glass-forming ability was fabricated by copper mould suction casting. Cubic AlCu 2 Zr and B2-ZrCu, thermal-induced martensitic B19'-ZrCu phases form on the glass matrix along the radial direction structure. Size effects on micro-mechanical properties and a unique crack healing behavior were studied. Micro-hardness of monolithic bulk metallic glass (BMG) displays “smaller is softer” trend, that is, the softer surface and the harder center. Whereas the lager size composites possess a softer center and a harder surface, due to the integrative action of the secondary phases. Amorphous matrix is toughened by TRIP (transition induced plasticity) effect of shape-memory phase as well as weakened and embrittled by AlCu 2 Zr crystal. After annealing, self-healing of Vickers indentation crack occurs as the thermoelastic transformation of shape-memory crystals. As loading, stress-induced martensites transform from B2 to B19', along with volume expansion. Annealed upon the reverse transformation temperature, B19' to B2 transform accompanied by a volume shrinkage, and a restoring force from the structure stress is set up to drive the crack closure.

Novel ultra-strong medium entropy bulk metallic glasses composites (BMGCs) Fe65.4&minus, xCexMn14.3Si9.4Cr10C0.9 and Ti40&minus, xCexNi40Cu20 (x = 0, 1.0), through the martensite transformation induced plasticity (TRIP effect) to enhance both the ductility and work-hardening capability, were fabricated using magnetic levitation melting and copper mold suction via high frequency induction heating. Furthermore, the Ce microalloying effects on microstructure and mechanical behaviors were studied. The Fe-based BMGCs consisted of face-centered cubic (fcc) &gamma, Fe and body-centered cubic (bcc) &alpha, Fe phase, as well as Ti-based BMGCs containing supercooled B2-Ti (Ni, Cu) and a thermally induced martensite phase B19&rsquo, Ti (Ni, Cu). As loading, the TRIP BMGCs exhibited work-hardening behavior, a high fracture strength, and large plasticity, which was attributed to the stress-induced transformation of &epsilon, Fe martensite and B19&rsquo, Ti (Ni, Cu) martensite. Ce addition further improved the strengthening and toughening effects of TRIP BMGCs. Adding elemental Ce enhanced the mixing entropy &Delta, Smix and atomic size difference &delta, while reducing the mixing enthalpy &Delta, Hmix, thus improving the glass forming ability and delaying the phase transition process, and hence prolonging the work-hardening period before fracturing. The fracture strength &sigma, f and plastic stress &epsilon, p of Ti39CeNi40Cu20 and Fe64.4CeMn14.3Si9.4Cr10C0.9 alloys were up to 2635 MPa and 13.8%, and 2905 MPa and 30.1%, respectively.

Cu46Zr44Al5Nb5 amorphous alloys were fabricated by suspend melting under an argon atmosphere using water-cooled Cu mould suction casting. Glass forming ability and mechanical properties of the alloys were studied. The analyses of DSC curves, X-ray diffraction (XRD) patterns and electron diffraction taken from the rods of Cu46Zr44Al5Nb5 with different diameters (3, 4, 6 mm) indicate that the critical diameter can be up to 6 mm at least. And the best glass former exhibits an undercooled liquid region ΔT of 52 K, and reduced glass transition temperature Trg of 0.60. The critical cooling rate (Rc) calculated from TTT (Time-Temperature-Transformation) curves of Cu46Zr44Al5Nb5 forming glassy alloy is 3.985 K/s. The intensity of broad peaks from X-ray diffraction patterns, the crystallization enthalpy and the fracture strength of the amorphous rods with different diameters, exhibit obvious difference, which is related to the variation of the cooling rate of solidification for the rods with different size.

In order to research the plasticity of the Cu-based bulk amorphous and the influence of rare earth element on the mechanical properties of the amorphous, the Cu50-xZr42Al8Gdx (x=0, 2, 4) alloy rods with 3.0 mm in diameter were prepared by the suspend melting-copper mold suction casting. The structure and glass forming ability of the alloys were analyzed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Subsequently, through the compression performance testing and the fracture morphology observation, the effect of rare earth element Gd on the mechanical performance and the fracture behavior of the samples were investigated. The results show that the structure of the rods is composed of amorphous phase. The samples possess larger thermal stability and good glass formation ability. With the increase of Gd content, the brittleness of the samples is enhanced gradually. Fracture mode presents brittle fracture.

Zr 53.9 Cu 29.4 Ni 4.9 Al 9.8 Fe 2 alloy sample with the diameter of 3 mm was prepared by Cu mold suction casting at different temperatures. The effect of casting temperature on mechanical properties and microstructure of the as-cast alloy was investigated. It is found that there is a critical casting temperature for the fully amorphous structure, below which the crystallization phase might be precipitated. Experiment results show that the compressive strength increases and the compressive plasticity slightly decreases when the casting temperature increases to certain extent. However, the compressive strength and the compressive plasticity simultaneously increase when the casting voltage increases to 9 kV, and the compressive plasticity is 2.62%. Mechanical properties of BMG can be tailored to certain extent by controlling the casting temperature, which is correlated with free volume and residual stresses.

The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied. The results show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current within the frequency range of pulse current. Imposed pulse current could induce the solidification system to oscillate. The frequency range and the relevant energy distribution of pulse current exert an influence on the amount of atoms involved for forming critical nucleus, the surface states of clusters in melt, the oscillating state of melt on the surface of clusters, the active energy of atom diffusion, the frequnce response of the resonance of bulk melt and the absorbability of the solidification system to the external work. Rectangle wave pulse current involves rich harmonic waves; the amplitudes of high order of harmonic waves are higher and reduce slowly, so it has a better effect on inoculation and modification.