The focus of this study is the thermomechanical characterization and comparison between two different shape memory alloys (SMAs) quantifying the effect of plastic strain on the transformation characteristics of SMA actuators. In this study, the thermomechanical response and transformation characteristics of a NiTiCu and a NiTi SMA are studied as a function of the induced plastic strain for four...

The structural and dynamic properties of the interface during the fcc-bcc transformation in pure iron have been investigated by molecular dynamics simulations. An embedded atom method potential was used for the atomic interactions. Two interfaces, close to the Bain and Kurdjumov-Sachs orientation relations, have been examined during the fcc-to-bcc transformation. In each simulation the system w...

The previous work of Professor W. G. Burgers and Dr. A. J. Bogers is used to develop a mechanism of strain-induced martensitic nucleation, involving two intersecting shear systems. We distinguish between strain-induced nucleation and stressassisted nucleation, the latter involving the same sites and embryos as does the regular spontaneous transformation. The strain-induced nucleation, on the ot...

A method based on the kinetics of crystal growth has been developed and applied to the computation of three-dimensional microstrucuture in austenite-matensite steels. The detailed crystallography of the transformation is used to model a realistic martensitic microstrucuture during the transformation without an external system of stresses. The interaction energy based on the plastic work model i...

In shape memory alloys the Thermoelastic Martensitic Transformation (TMT), intrinsically stepwise, can be either thermally induced or stress-induced. Moreover, it has already been shown that an extrinsic fragmentation of thermally induced transformation can be stimulated ("Step-wise Martensite to Austenite Reversible Transformation", SMART) by means of Incomplete Cycles on Heating (ICHs): the S...

Structural phase transformations in the ferromagnetic FeNi alloys is discussed on the basis of first-principles and molecular-dynamics simulations. In the molecular-dynamics study effective potentials have been used which were derived by the Embedding Atom Method. The simulations reproduce fairly well the austenitic transformation upon heating, while for the martensitic transformation upon cool...

Heat treatment and stress state effects on the martensitic transformation in [001] and [123] oriented single crystal Ni54Fe19Ga27 alloys are determined. Characteristic temperatures increase for longer aging times and higher hold temperatures. The non-aged [001] crystals exhibit the smallest stress hysteresis and lowest critical stress in tension. The experimental results are interpreted based o...

Martensitic transformations are diffusionless solid-to-solid phase transformations characterized by a rapid change of crystal structure, observed in metals, alloys, ceramics, and proteins. They come in two widely different classes. In steels, the transformation microstructure induced by quenching remains essentially unchanged upon subsequent loading or heating; the transformation is not reversi...

Effects of magnetic fields and hydrostatic presswes on the isothermal martensitic transformation, whose nose temperature is about 140% in an Fe-25.ONi-4.OCr alloy ( mass% ) has been examined by applying magnetic fields up to 30MA/m and hydrostatic presswes up to 1.SGPa The obtained results are the following: The martensitic transformation is induced instantaneously ( less than 20psec.) under pu...