Combinatorial nanocalorimetry and synchrotron x-ray diffraction were combined to study the martensite-austenite (M-A) phase transformation behavior of Ni-Ti-Hf shape memory alloys. A thin-film library of Ni-Ti-Hf samples with a range of compositions was deposited on a parallel nano-scanning calorimeter device using sputter deposition. Crystallization of each amorphous as-deposited sample by loc...

A high damping capacity is considered as one of the important functional properties of shape memory alloys. Those properties are related to a thermoelastic martensitic transformation. As a consequence of this transformation, the internal friction or damping can be investigated for three different states: 1. during thermal transformation cycling, 2. during martensite induced strain cycling at co...

This work presents a unique approach for the modelling of the austenitisation of martensite in dual-phase steels within the phase-field method. Driving forces for nucleation and growth are derived from thermodynamic databases. Routines for nucleation are based on a discretisation of the classical nucleation theory. Validation is given via dilatometric experiments.

Crystallographic reconstruction of parent austenite grain boundaries from the martensitic microstructure in a wear resistant steel was carried out using electron backscattered diffraction (EBSD). The present study mainly aims to investigate the parent austenite grains from the martensitic structure in an as-rolled (reference) steel sample and samples obtained by quenching at different cooling r...

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...

We have investigated the relation between the softening of elastic constants and martensitic transformation in Fe3Pt, which exhibits various kinds of martensitic transformation depending on its long-range order parameter S. The martensite phases of the examined alloys are BCT (S = 0.57), FCT1 (S = 0.75, c/a < 1) and FCT2 (S = 0.88, c/a > 1). The elastic constants C′ and C44 of these alloys decr...

Phase transformation temperature is one of the most important parameters for the shape memory alloys (SMAs). The most popular method to determine these phase transformation temperatures is the Differential Scanning Calorimeter (DSC), but due to the limitation of the DSC testing itself, it made it difficult for the finished product which is not in the powder form. A novel method which uses the U...

Recent experiments have revealed a rich variety of strain states in doped ferroelastic systems. We study the origin of two abnormal strain states; precursory tweed and strain glass, and their relationship with the well-known austenite and martensite (the para- and ferroelastic states). A Landau free energy model is proposed, which assumes that point defects alter the global thermodynamic stabil...

Strong steels also have to be tough and hence rely on fine microstructures such as bainite or martensite, produced commercially by continuous cooling transformation. Depending on the detailed requirements, the steel-design process may explicitly require other higher temperature phases to be absent in the final microstructure. Such a procedure can be made easier by the availability of a good met...

The nucleation and growth mechanisms of Ni5A13 precipitates and microtwinned plates in B2 austenite and 2M (3R) martensite phases are described on the basis of conventional and high resolution electron microscopy. In the Ni62.5A137.5 B2 austenite matrix short annealings at 550°C introduce three-pointed star shaped precipitates consisting of twin related parts of different variants of the Ni5A13...