Engineering Twins and Stacking Faults of Co-Al-W Shape Memory Alloy by a Combination of Casting and Solution-Treatment

We first constructed twin-free and coarse austenite grains by simple casting in a Co-6.8Al-6.3W shape memory alloy. Subsequently, a high density of stacking faults was induced by solution-treating at 1573K for 5 h in the cast Co-6.8Al-6.3W alloy. As a result, a large recovery strain of 5.7% was achieved in the solution-treated cast Co-6.8Al-6.3Walloy because three conditions of microstructure design, i.e., coarse austenite grains, twin-free microstructure and the high density o fstacking faults, were satisfied simultaneously. The combination of casting and solution-treatment should be an effective way to engineer twins and stacking faults in other Co-based alloys.