(Fe1-xVx)3Al合金(x≤1/3)の高温変形挙動に及ぼす規則-不規則変態の影響

Abstract

The mechanical properties of (Fe1-xVx)3Al alloys including the Heusler-type Fe2VAl (x=1/3) have been investigated using high-temperature compression tests with attention to an increase in the D03(L21)-B2 transition temperature Tc by the V substitution. The yield stress peak substantially shifts to higher temperatures with increasing Tc and can be found at around 1270 K for Fe2VAl. The strain rate sensitivity exponent m is near zero in the temperature range where the plateau with a rather low yield stress appears, but rises sharply around the peak temperature, reaching m=0.40 at 1300-1400 K for Fe2VAl. Thus superplastic behavior is always expected to occur in the (Fe1-xVx)3Al system when deformed at temperatures above that of the yield stress peak under a strain rate range of 10-4-10-3 s-1. In spite of large-grained Fe2VAl, the grain size becomes much finer after deformation up to a strain of 120%: from about 400 μm to 30 μm. Dynamic recovery and recrystallization process similar to that in Fe3Al is proposed as the superplastic deformation mechanism.