Effect Of Microstructures On Mechanical Properties And Adiabatic Shear Behavior In Ti-6Al-4V Alloy

Titanium alloy has great potential in the field of armor protection for its excellent properties. This paper formulated the different heat treatment systems, obtained with different fine structure characteristics of the organization. The various microstructures of TC4 titanium alloy underwent static tensile tests and dynamic impact tests, were studied by optical microscope and scanning electron microscope, and revealed the effects of volume fraction of transformed β matrix and width of αs plates on dynamic mechanical properties and adiabatic shear sensitivity of TC4 titanium alloy. The main research conclusions were as follows:Bimodal microstructures of TC4 alloy with different volume fraction of transformed β matrix and different width of αs plates were obtained via heat treatment involving different solution temperature and cooling rate. And the volume fraction of transformed β matrix increased with increasing solution temperature, while the width of αs plates increased with decreasing cooling rate.In the quasi static tests, the strength and hardness of the bimodal microstructures of TC4 alloy increased with the increasing volume fraction of transformed β matrix, and reached its maximum value when the volume fraction of transformed β matrix was 80.7%, then decreased when the volume fraction of transformed β matrix continued to increase. The strength and hardness also decreased with the increasing width of αs plates. Meanwhile, the strain increased with increasing width of αs plates.In the dynamic compression tests, the dynamic compressive strength of the bimodal microstructures of TC4 alloy increased with the increasing volume fraction of transformed β matrix, and reached its maximum value when the volume fraction of transformed β matrix was 80.7%, then decreased when the volume fraction of transformed β matrix continued to increase. The dynamic compressive strength also decreased with the increasing width of αs plates. Meanwhile, the strain decreased with increasing volume fraction of transformed β matrix, while increased with increasing width of αs plates.In the forced shear tests, the adiabatic shear sensitivity decreased with increasing volume fraction of transformed β matrix, and reached its minimum value when the volume fraction of transformed β matrix was 80.7%, then increased when the volume fraction of transformed β matrix continued to increase, it also decreased with increasing width of αs plates.In the dynamic compression tests of precise control of strain, the critical strain and the energy which were needed in producing adiabatic shear bands in the bimodal microstructures of TC4 titanium alloy with, increased with the increasing volume fraction of transformed β matrix, and reached its maximum value when the volume fraction of transformed β matrix was 80.7%, then increased when the volume fraction of transformed β matrix continued to increase. The bimodal microstructure of titanium alloy with the volume fraction of transformed β matrix which was 80.7%, has the lowest adiabatic shear sensitivity; the critical strain and the energy which were needed in producing adiabatic shear bands in the bimodal microstructures of TC4 titanium alloy, increased with the increasing width of αs plates.