The electronic structure and magnetism of the Heusler alloy Mn2NiAl have been studied by firstprinciples calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, ferromagnetic sha...

This paper proposes a method to calculate the uniaxial stress /strain relationship of polycrystalline Fe /Pd, which has a martensite structure produced by cooling. Strain is caused by changes in the fractions of the three Bain corresponding variants which form the martensite structure within each grain. Internal stress and elastic energy are accumulated as straining proceeds and are caused by d...

A phase-field theory of transformations between martensitic variants and multiple twinning within martensitic variants is developed for large strains and lattice rotations. It resolves numerous existing problems. The model, which involves just one order parameter for the description of each variant-variant transformation and multiple twinnings within each martensitic variant, allows one to pres...

The decomposition of martensite during tempering or ageing is an important phenomenon as it leads to changes in the mechanical properties. These changes could take place during both steel manufacturing or in-service. Thus, their understanding is required to predict the material performance. Recent advances in the development of local electrode atom probes has led to a significant increase in th...

In this study, two CCCT diagrams are drawn to be compared with a CCT diagram. The CCCT diagrams represent continuous cooling transformations in stress assisted state. The increased Md and Bd temperatures of CCCT diagrams were also compared with those of the CCT diagrams and the cause was investigated from both thermodynamic and metallurgical viewpoints. Thermodynamic examinations revealed that ...

In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second harden...

Modeling of shape-memory alloys represents a multiscale problem due to occurrence of martensite/austenite phase transformation and a microstructure in the deformation gradient typical for martensitic phase. Inspired by relaxation in static situation, a limit passage between two modeling scales, called microand meso-scales, is performed for the corresponding evolution variants with considering a...

Shape memory and magnetic properties of a Ni43Co7Mn39Sn11 Heusler polycrystalline alloy were investigated by differential scanning calorimetry, the sample extraction method, and the three-terminal capacitance method. A unique martensitic transformation from the ferromagnetic parent phase to the antiferromagneticlike martensite phase was detected and magnetic-field-induced “reverse” transition w...

Effects of ultra high magnetic field of both pulse and steady types on martensitic transformation have been studied, using Fe-Ni-Mn, Fe-Ni-Mn-C alloys with the supplemental tests on Fe-Ni-C and Fe-NiCo-Ti alloys. It is found that the martensitic transformation is induced at room temperature not only athermally but also isothermally either by pulse magnetic field or by steady magnetic field for ...

The microstructure of 8 mm diameter wire produced by the severe deformation of 316L austenitic stainless steel has been examined using TEM and X-ray diffraction. The deformation imparted amounts to a true strain of 6.3. Data from previous studies on strain induced transformation of this steel have been combined with new results to show that true strains .2 are required in order to observe mecha...