Effect of B on Shape Memory Properties and Microstructure of Fe14Mn6Si9Cr5Ni Alloy and Its Mechanism

The shape memory performance of the Fe-Mn-Si shape memory alloy is not satisfactory due to irreversible plastic deformation during the martensitic transformation process. In this paper, Fe14Mn6Si9Cr5Ni alloys with different B additions were prepared by arc additive manufacturing using Fe14Mn6Si9Cr5Ni-xB alloys with good overall performance. The memory properties of the prepared alloys were investigated, the microstructure of the alloys was analyzed, and the mechanism of B's influence on the shape memory alloys was discussed. The results showed that adding B improved the alloy's recoverable strain. The recoverable strain of a Fe14Mn6Si9Cr5Ni-xB alloy can reach up to 3.01% when 0.05 wt.% of B is added. The analysis indicated that the addition of B reduced the alloy's stacking fault energy, increased the strength of the parent phase, and increased the number of stress-induced martensite. However, when B is added above 0.1 wt.%, larger-sized borides precipitate in the alloy. These larger-sized borides exhibit a pinning effect, causing cross-growth of martensite and deteriorating the memory performance of the alloy.