Effect of the Manufacturing Process on the Texture and the Fraction of Stress-induced Martensite in an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

Fe-Mn-Si based alloys exhibit the shape memory effect (SME) through a γ(FCC) ↔ ɛ(HCP) stress-induced martensitic transformation. Studies carried out with single crystals have shown that the extent of shape recovery depends on the crystal orientation: it is nearly absent if the stress acts along the [001] direction and almost perfect when applied in the [414] direction. Therefore, certain crystallographic textures in polycrystals may contribute to better shape recovery with less applied stress. On the other hand, the texture is a consequence of the thermal and mechanical material processing history. This study analyzes how the particular forming process and the consequent texture development affects the amount of stress-induced ɛ martensite in an Fe-15Mn-5Si-9Cr-5Ni shape memory alloy. Besides determining the quantity of martensite produced, we measured the critical transformation temperatures and analyzed the effect of the manufacturing procedures on the SME properties.