Motivated by experimental observations of H. Seiner et al., we study the nucleation of austenite in a single crystal of a CuAlNi shape-memory alloy stabilized as a single variant of martensite. In the experiments the nucleation process was induced by localized heating and it was observed that, regardless of where the localized heating was applied, the nucleation points were always located at on...

Ni based magnetic shape memory alloys (MSMAs) have broad applications in actuators and MEMS devices. Two-stage stress induced martensitic phase transformation, a widely observed phenomenon in these alloys, is described conventionally as a fi rst stage L21 (austenite)-to-10M/14M (M: modulated martensite) transition, followed by a second stage 14M-to-L10 (tetragonal martensite) transformation at ...

For Fe-Mn-Si-Cr-Ni shape memory alloys, it was previously found by HREM study that the formation of the nanometric lamella structures consisting of f.c.c. and h.c.p. phase is very important to exhibit good shape memory effect. In the present work, the formation process of such lamella structures has been studied in detail. The results are as follows. The transformation is initiated by random fo...

In this study, the effects of nitrogen addition on the production of ultrafine/nano grained AISI 201L stainless steel by advanced thermo-mechanical process were investigated. Cast samples were first homogenized at 1200 °C for 4 h, hot-rolled at 1100 °C and finally, solution-annealed at 1150 °C for 2.5 h. Unidirectional and cross multipass cold rolling at 25 °C was carried out to 90% reduction i...

It has been clarified that deformation and annealing of martensite starting structure can produce ultrafine-grained structure in low carbon steel.  This study aims to investigate the texture evolution and mechanical properties of samples with martensite structure deformed by two different forging processes. The martensitic steel samples were forged by plane strain compression and multi-directio...

the unique properties of air-cooled bainitic steels have been described. a series of mn containing air-cooled bainitic steels invented by authors is presented in this paper: including low carbon granular bainitic steels, low carbon grain-boundary allotriomorphic ferrite/granular bainite duplex steels, medium and medium high carbon bainite/martensite duplex steel, and low carbon carbide free bai...

Magnetic shape memory properties of Ni-Mn-Ga single crystals were characterized by measurement of stress-induced martensite reorientation under constant magnetic fields. Also magnetic field-induced strain as a function of the applied magnetic field under different constant compressive stress levels has been investigated. All the experiments were performed at room temperature in which the sample...

Differential scanning calorimetry (DSC) was used to determine the transition temperature ranges (TTR) of four types of super-elastic orthodontic nickel-titanium coil springs (Sentalloy). A knowledge of the TTR provides information on the temperature at which a NiTi wire or spring can assume superelastic properties and when this quality disappears. The spring types in this study can be distingui...

The crystallography of B2 to R-phase and the subsequent R-phase to B19′ martensite transitions was analysed in NiTi alloys. Using the energy minimization theory of martensitic transformations, the habit plane and twin plane normals were established for the R-phase, B19′ martensite variants as a function of rhombohedral angle . Two types of twins, classified as {1 0 0}〈0 1 1〉 and {1 1 0}〈0 0 1〉 ...

Austenitic NiTi samples were cathodically charged with hydrogen to produce concentrations ranging from a baseline value of 9 wppm to 650 wppm. The effect of hydrogen on the phases and transition temperatures of NiTi was studied with X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile testing, and scanning electron microscopy (SEM). XRD analyses showed the B2 peaks shifting...