P. La Roca

Relationship between martensitic plate size and austenitic grain size in martensitic transformations

A systematic experimental analysis based on an assessment of the mean martensite plate size (hplate) in sub-grain domains was implemented to characterize the martensite morphology in polycrystalline Cu-based shape memory alloys. In the grain size range below 100 μm, a linear relationship between the average width of the martensite plates and the mean grain size was obtained for a thermal-induced martensitic transformation. This evaluation allows us to perform an analysis of how microstructural length scales affect the martensitic transformation.

Shape-Memory Effect and Pseudoelasticity in Fe–Mn-Based Alloys

Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe–Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe–Mn–Al–Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc–hcp in the first case and the bcc–fcc in the latter are discussed. Selected potential applications are also analyzed.