Microstructure transformation due to thermomechanical processing has an acute effect the macroscopic properties of low-carbon steels. This includes viscoplastic deformation and phase transformations. Hot forming processes such as press hardening are particularly affected. Most engineering applications require a combination high strength sufficient residual ductility, which can be achieved by de...

Lath martensite reveals a specific hierarchical subgrain structure, with laths, blocks and packets of particular crystallography. The presence of interlath retained austenite layers has been reported in the literature. This paper investigates the potential influence of the interlath retained austenite on the mechanical behaviour of lath martensite subgrains. To this purpose, a martensite grain ...

Ni39+x Mn50Sn11-x (x = 0.5, 1.0, 1.5 and 2) alloys comprise multiple martensite nanostrips of nanocrystallites when cast in small discs, for example, ∼15 mm diameter and 8 mm width. A single martensite phase with a L10 tetragonal crystal structure at room temperature can be formed at a critical Sn content of 9.0 at.% (x = 2), whereas an austenite cubic L21 phase turns up at smaller x ⩽ 1.5. The...

We study the behavior of crystals that undergo martensitic transformations. On cooling, the high-temperature phase (austenite) transforms to the martensite phase changing its crystalline symmetry. The lower crystalline symmetry of the martensite gives rise to several variants of martensite. Each variant has an associated transformation strain. These variants accommodate themselves (according to...

Stimulated by recent experimental results on superelastic NiTi shape memory alloy, a theoretical study is carried out to quantify the effect of plasticity on stress-induced martensite transformation, using a constitutive model that combines phase transformation and plasticity. A constraint equation is introduced to quantify the phenomenon of the stabilisation of plasticity on stress-induced mar...

This work focuses on the stress-induced transformation in solutionized and overaged single-crystal NiTi alloys. The potential role of detwinning on the recoverable strains was investigated both theoretically and also with temperature-cycling experiments. The detwinning is the growth of one variant within a martensite in expense of the other. It is shown that the experimental recoverable strains...