The background to this bachelor thesis is an on-going project within the VINN Excellence Center Hero-m. The task in this thesis is to perform a literature survey about the martensite transformation and investigate how the resulting fraction depends on cooling below the Ms-temperature. Instead of calculating the undercooling for each of the known fractions of martensite the driving force will be...

The classification of martensitic displacive transformations into athermal, isothermal or anisothermal is discussed. Athermal does not mean “no temperature dependence” as is often thought, but is best considered to be short for the notion of no thermal activation. Processes with no thermal activation do not depend on time, as there is no need to wait for sufficient statistical fluctuations in s...

Thermodynamically consistent, three-dimensional (3D) phase field approach (PFA) for coupled multivariant martensitic transformations (PTs), including cyclic PTs, variant– variant transformations (i.e., twinning), and dislocation evolution is developed at large strains. One of our key points is in the justification of the multiplicative decomposition of the deformation gradient into elastic, tra...

The resistivity anisotropy unveiled in the study of detwinned single crystals of the undoped 122 pnictides is here studied using the two-dimensional, three-orbital Hubbard model in the mean-field approximation. Calculating the Drude weight in the x and y directions at zero temperature for a Q = (π,0) magnetically ordered state, the conductance along the antiferromagnetic direction is shown to b...

the microstructure of dual phase steels can be considered as a matrix of ferrite phase reinforced by martensite particles. recent measurements show that the mechanical properties of the ferrite phase are changed with the distance from the martensite grains. in this paper, a new method has been proposed to consider this phenomenon in finite element modeling of dual phase steels microstructure. i...

Nano-structured NiTi instantaneously transforms from fcc austenite via an intermediate phase (the R-phase) into monoclinic B19’ martensite. At a grain size less than a critical limit of about 50nm no transformation can be observed even upon cooling down to cryogenic temperatures. In slightly larger grains the martensite appears as a laminate of alternating twinrelated Bain correspondence varian...

This paper provides an overview on obtaining low-carbon ultra-fine grained dual-phase steels through rapid intercritical annealing of cold-rolled sheet as improved materials for automotive applications. A laboratory processing route was designed that involves cold-rolling of a tempered martensite structure followed by a second tempering step to produce a fine grained aggregate of ferrite and ca...