Recovery stress formation in FeMnSi based shape memory alloys: Impact of precipitates, texture and grain size

Publication date: 5 February 2018
Source:Materials & Design, Volume 139
Author(s): A. Arabi-Hashemi, W.J. Lee, C. Leinenbach
FeMnSi based shape memory alloys are considered for engineering applications such as prestressing of concrete or coupling devices. For this, a high recovery stress is desired which forms when the FeMnSi alloy is first elongated and then heated above the austenite transformation temperature under mechanical constraints. In this work, we study the impact of three different microstructural properties on the recovery stress of Fe17Mn5Si10Cr4Ni1(V,C) shape memory alloys: Precipitates, texture and grain size. Precipitates allowed varying the recovery stress in a broad range between 255MPa and 564MPa. A recovery stress of 564MPa was achieved by a combination of a high materials yield strength σ0.1 of 536MPa and a shape recovery of 14%. The [001] grain orientation with a low Schmid factor has a beneficial impact on the recovery stress due to a higher yield strength when compared with the [011] orientation. A decrease of the grain size caused a Hall-Petch strengthening but had no influence on the recovery stress. However the pseudo-elasticity increased for a decrease of grain size.

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