Dynamic tension tests were employed to investigate the effect of strain rate on mechanical behaviors of Ti10V2Fe3Al and 30CrMnSiNi2A. The strain rate ranges from 10 -4 to 10 3 s -1 . Experimental results showed that the yield strength ( σ s), ultimate strength( σ u) and elongation( δ 5) increase, but strain hardening exponent( n ) decreases with the rise of strain rate( ) by refractive lines. The reasons that σ s and σ u increase with increasing are concerned with thermal activation. The high strain rate induced increasing plasticity is associated with adiabatic heating of specimen, impact twinning and suppression of strain induced phase transformation. Strain hardening exponent n can be considered a constant under quasi static loading, but decreases rapidly till an ideal plastic state( n =0) after strain rate surpassing a critical value(10 2 s -1 ). The mechanism of n decreasing with the increase of is related to the increase of σ s and suppression of strain induced phase transformation.
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