Dynamic Mechanical Responses And Deformation Mechanisms Of In-situ Metallic Glass Matrix Composites

Bulk metallic glasses(BMGs)are advanced structure materials with a wide range of applications due to their high strength,large elastic limit,superior corrosion,and wear resistance.However,almost all the BMGs exhibit catastrophic brittle failure at ambient temperature due to the prompt propagation of highly localized shear bands upon loading.The actual engineering applications of BMGs are hindered by their room temperature brittleness and strain softening nature,such as armor materials,while crystalline alloys present superior plasticity under loading.Therefore,these shortcomings are addressed with the development of in-situ metallic glass matrix composites(MGMCs),two-phase alloys consisting of glass matrix and crystalline dendrites.MGMCs retain the high strength and enhanced ductility corresponding to BMGs and crystalline alloys,respectively,which contributed to considerable plasticity and strain hardening upon quasi-static and dynamic loadings.In this paper,experiment verification,microscopic mechanism analysis,constitutive model and finite element model are combined to reveal the inherent relationship between microstructure evolution and mechanical properties.An in-situ Ti-based metallic glass matrix composite,Ti43Zr32Ni6Ta5Be14,presents ideal elastic-plastic and plastic flow upon dynamic compression.The ideal elastic-plastic is mainly attributed to the dynamic equilibrium between the dislocation mechanism within the crystalline dendrites,structural softening mechanisms within the glass matrix,and thermal softening within MGMC.The plasticity of the composite is semi-quantitatively analyzed by the matching relation of shear band toughness between the glass matrix and crystalline dendrites.Furthermore,strain-rate effect of the microstructure evolution on yield strength is characterized by employing the dislocation-based Zerilli and Armstrong(ZA)model,the cooperative shear model(CSM)associated with the adiabatic temperature rise in the shear transformation zone(STZ),together with the modified CSM model related to viscosity,respectively.A novel transformation-induced plasticity-reinforced metallic glass matrix composite,Ti40Ni38Ce2Cu20,with face-centered cubic B2 phase and monoclinic B19’ phase as well as amorphous phase,exhibits extensive strain hardening and high compression yield and fracture strength upon dynamic loading.Martensitic transformation(MT)with supersonic characteristic takes place in the form of shearing,which can significantly improve the dynamic strain hardening ability of MGMC,while the dislocation accumulation is difficult to occur at high strain rate.TRIP effect makes a significant improvement in the dynamic mechanical properties of MGMC,which provides a new strategy for the application as a novel structural material in high-speed and high-energy fields.The concept of twinning induced plasticity(TWIP)is futher introduced into the crystalline phase via microalloying,which makes MGMC retain the TRIP effect and gain TWIP effect,to optimize the mechanical properties of TRIP-reinforced MGMC upon dynamic loading.The MT and twins can easier take place by properly increasing the content of Ni,which can reduce the stacking fault energy,while the addition of Ce element can significanty improve the glass forming ability of MGMC.Therefore,a novel in-situ metallic glass matrix composite reinforced by TRIP and TWIP effects with a nominal composition of Ti40Ni39Ce1Cu20(at.%)is fabricated via regulating composition and exhibits extensive strain hardening and considerable plasticity under quasi-static and dynamic compression.In addition,based on the microstructure evolution of metastable crystalline and amorphous phase before and after compression,finite element analysis is employed to reveal the microstructure origin for plastic deformation homogenization of MGMC upon dynamic loading.