The purpose of this review was to investigate the correlation between magnetism and crystallographic structures as it relates to the martensite transformation of Ni2MnGa type alloys, which undergo martensite transformation below the Curie temperature. In particular, this paper focused on the physical properties in magnetic fields. Recent researches show that the martensite starting temperature ...

Shape memory alloys exhibit a high damping capacity in the mktensite state. Results obtained from both DMA and cyclic tests under tension-compression load show that the martensite damping capacity in NiTi SMAs is a function of both strain amplitude and annealing temperature. Internal friction due to movements of martensite twin boundaries within both elastic (accommodation) and inelastic (reori...

The name martensite is after the German scientist Martens. It was used originally to describe the hard microconstituent found in quenched steels. Martensite remains of the greatest technological importance in steels where it can confer an outstanding combination of strength (> 3500MPa) and toughness (> 200MPam 1 2 ). Many materials other than steel are now known to exhibit the same type of soli...

The shape memory effect exhibited by Fe-Mn-Si based alloys is due to the y(f.c.c.)-e(h.c.p.) martensitic transformation. The martensitic transformation induced by traction at room temperature in a Fe16Mn-9Cr-5Si-4Ni (%mass) is here studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and scanning tunnelling microscopy. The martensitic microstructure and ...

It is increasingly important in the context of high–manganese steels of the kind that lead to twinning–induced plasticity to be able to estimate the temperature at which ε–martensite forms when austenite is cooled. We find that the thermodynamic method used in similar calculations for α martensite cannot in many cases be implemented because of apparently imprecise thermodynamic data, a conclusi...

The formation of stress-induced α′′ martensite in a metastable β Ti-Mo-based alloy has been studied using X-ray diffraction and transmission electron microscopy. The martensite nucleates heterogeneously at pre-existing sub-grain boundaries by dissociation of the boundary dislocations which bow out on inclined planes. The growth of martensite laths from the resultant stacking faults occurs by th...

This conference paper briefly discusses different techniques for measuring the evolution of the martensite content in cold-rolled stainless steel 301LN sheets under mechanical loading. Three methods are employed to measure the martensite content: (1) micrography, (2) bulk magnetic induction, and (3) local magnetic permeability measurements. The first two methods require the extraction of sample...

Modulated phases occur in numerous functional materials like giant ferroelectrics and magnetic shape-memory alloys. To understand the origin of these phases, we employ and generalize the concept of adaptive martensite. As a starting point, we investigate the coexistence of austenite, adaptive 14M phase, and tetragonal martensite in Ni-Mn-Ga magnetic shape-memory alloy epitaxial films. We show t...

The experimental facts on the stabilisation of martensite in copper base shape memory alloys, of interest to the scientific investigator and the practical alloy processor and user are reported. Factors that have an influence on stabilisation are considered in this respect. The mechanisms proposed in the literature to explain stabilisation are critically examined.

spear-like martensite thermally formed in the same alloy in several respects such as in shape, lattice invariant shear, habit plane and orientation relationship, even though both have the same crystal structure and lattice parameters. The lattice invariant strain of the martensite was found to be stacking faults on the basal plane, and a defectless region was observed at the middle of the marte...