Effects of grain size on deformation behavior of heusler-type Fe2VAl alloys

Abstract

The deformation behavior of fine-grained Heusler-type Fe2VAl alloys (average grain diameter d= 14, 2.0, 1.4 and 0.4 μm) made by pulse current sintering (PCS) has been investigated in comparison with the arc-melted alloys with d= 130 μm. The yield stress of the Fe2VA1 alloys at 300 K increases as the grain size decreases, following the Hall-Petch relationship except for d = 0.4 |im. An anomalous increase in the yield stress with increasing temperature can be observed for d=14 and 130 μm, whereas the yield stress peak disappears for d≤2.0 μm. The yield stress decreases at a lower temperature for finer grains, which occurs in parallel with a steep rise in the strain rate sensitivity exponent m. The m value for d = 2.0 μm reaches the maximum of 0.32 at 1123 K, and the temperature is almost 200 K lower than that for d= 130 μm. The decrease in the yield stress can be explained by a lower temperature superplasticity for finer grained alloys.