Study of strain rate sensitivity exponent and strain hardening exponent of typical titanium alloys

Abstract

In this study, the flow stress-strain curves of three typical titanium alloys, cast TA15 titanium alloy (near α-type), cast Ti40 titanium alloy (full β-type) and cast TC21 titanium alloy (α + β-type), were obtained based on hot compression tests, based on which the deformation activation energy, softening fraction, strain rate sensitivity exponents and strain hardening exponents of the three typical titanium alloys were calculated under different process parameters and analyzed The variation law of each parameter was analyzed. The effect of nascent grain size on the strain rate sensitivity exponent and strain hardening exponent was analyzed by counting the dynamic recrystallization grain size of the alloy. The results show that the deformation activation energy of Ti40 titanium alloy is much higher than that of TA15 and TC21 titanium alloys during thermal deformation, mainly because the alloying element content of Ti40 titanium alloy is much higher than that of the other two. The maximum value of strain rate sensitivity exponents m is obtained at the minimum strain rate for all three titanium alloys, and the deformation temperature also has a great influence on the value of m. Combined with the microstructure of the material under different deformation conditions, it is found that the effect of strain and strain rate on the strain hardening exponents n is very significant. Moreover, grain refinement during deformation can effectively increase the strain rate sensitivity exponent and reduce the strain hardening exponent.