Effect of second-phase particles on shape memory in Fe-Mn-Si-based alloys

The shape memory behaviour of two Fe-Mn-Si-based alloys has been investigated. One alloy was a reference alloy, and the other alloy was similar in composition except that it contained 0.55 wt% Ti. Following solution treatment and quenching, strip samples were subjected to three types of treatments; isothermal holding, cold rolling followed by isothermal holding, and hot rolling followed by isothermal holding. These treatments resulted in the formation of intermetallic precipitates in the Ti-containing alloy, while the reference alloy remained precipitate-free. In comparing the shape memory of the reference and the particle-containing alloy after identical heat treatments, it was found that the formation of precipitates had a beneficial effect on the shape memory in all cases. In general, the larger precipitates caused a larger increase in the shape memory. The effect of particle size on shape memory has been analysed using the current data and published results for a range of precipitate types.