Effects Of Temperature And Strain Rate On High Temperature Mechanical Properties Of Al Based Amorphous Alloys

Al based amorphous alloys have excellent properties,such as high strength,good toughness,excellent corrosion resistance and so on.They are widely used in engineering structures.In recent years,researchers at home and abroad have paid much attention to them.It was previously reported that the amorphous alloys had no macroscopic plastic deformation and belonged to shear deformation at room temperature.Macroscopic plastic deformation occurs in the supercooled liquid region,which is attributed to the glass transition behavior of amorphous alloys.It is reported that there is an obvious strain hardening phenomenon in the high temperature deformation of Al based amorphous alloys.However,the studies on the mechanical properties of this kind of materials are not systematically summarized and explained.This dissertation takes Al₈₇Gd₆Ni₇ amorphous alloy as the research object,and samples are prepared by melt quenching method.The high temperature mechanical properties were studied by adjusting the temperature and strain rate,and the morphology and microstructure of the material were analyzed.Set the initial strain rates were 6.67?10^-5s^-1,1.33?10^-4s^-1,3.33?10^-4s^-11 and 6.67?10^-4s^-11 and the temperature in the range of 160?to 260?,and then tensile tests were carried out to test the stress strain and fracture behavior.The conclusions are as follows.Under the condition of uniaxial tensile load,the tensile process is characterized by elastic stage,viscous flow,strain hardening and fracture.When the temperature is below the temperature of 187?,no strain hardening occurs.When the temperature exceeds 187?,both softening and strain hardening appear.When the strain rate is constant,with the increase of temperature,the yield strength and linear elastic strain decrease,while the elongation increases gradually.When the temperature is constant,with the increase of strain rate,the yield strength increases,while the elongation decreases.In other words,the plastic deformation capacity gradually decreases.Under the condition of high temperature,the strain hardening of amorphous alloy is due to the dynamic crystallization.The tensile fracture morphology is mainly a vein like pattern,and spreads along the shear plane.The amorphous alloy belongs to ductile shear fracture.In addition,the droplet shape can be observed,which shows that the local temperature in the region is more than the glass transition temperature T_g.Above the crystallization temperature,the width of veins increases with the increase of temperature.In other words,the density of veins decreases and the plasticity of the material increases.The width of veins gradually decreases with the increase of strain rate,that is,the density of vein veins increases,and the plasticity of materials decreases.