Effect of direct aging on microstructure, mechanical properties and shape memory behavior of Fe-17Mn-5Si-10Cr-4Ni-(V, C) shape memory alloy fabricated by laser powder bed fusion

In the present study, the effect of two distinct heat treatment conditions on microstructure, mechanical, and shape memory properties of Fe-17Mn-5Si-10Cr-4Ni-(V, C) (wt%) Fe-based shape memory alloy fabricated by laser powder bed fusion (L-PBF) was investigated. Sample directly aged (DA) at 750 degrees C for 6 h from the as-built state contained elongated fcc-gamma grains with a high amount of low angle boundaries, while sample aged after solution treatment (SA) at 1050 degrees C for 2 h showed fully recrystallized equiaxed grains with annealing twins. The DA had finer vanadium carbide (VC) precipitates that were more densely dispersed than the SA. Furthermore, VC precipitates in the DA were formed mostly along the solidification cell boundaries, resulting in the preservation of the solidification cell structure. The DA and the SA showed similar pseudo-elasticity and recovery strains. On the other hand, the yield strength and the recovery stress of the DA were much higher than those of the SA. The high yield and recovery stresses of the DA in comparison to the SA could be ascribed to the fine solidification cell structures and finely distributed VC precipitates in the direct aging followed by rapid solidification of the L-PBF process.