A microstructure consisting of ultrafine grained (UFG) ferrite with average grain size of ~ 0.7 µm and dispersed nano-sized carbides was produced by cold-rolling and tempering of the martensite starting microstructure in a low carbon steel. Subsequently, fine grained dual phase (DP) steel consisting of equiaxed ferrite grains with average size of ~ 5 µm and martensite islands with average size ...

The objective of this work was to study materials subjected to external loading where alternative deformation mechanisms are available to generate strains. In the case of shapememory and superelastic NiTi, these mechanisms are twinning and stress-induced phase transformation, respectively. Superelastic NiTi (51.0 at.% Ni) reinforced with 0, 10 and 20 vol.% TiC particles was fabricated by Hot Is...

Mechanical devices are sought to support insufficient or paralysed striated muscles including the failing heart. Nickel-titanium alloys (nitinol) present the following two properties: (i) super-elasticity, and (ii) the potential to assume different crystal structures depending on temperature and/or stress. Starting from the martensite state nitinol is able to resume the austenite form (state of...

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the...

The investigations till now performed on the Step-wise Martensite to Austenite Reversible Transformation (SMART) have identified the relevant key features both of the transformation itself and of the Incomplete Cycling on Heating (ICH), procedure required to induce the SMART. The SMART phenomenology, proved in several shape memory alloys, appears quite general, despite of the differences both i...

The structural changes occurring during tempering of Fe-N martensite (a') have been investigated using X-ray diffraction and (high resolution) transmission electron microscopy. The first stage of decomposition of Fe-N martensite leads to the formation of &-nitride and ferrite (a). The formation of a"-nitride involves both a local enrichment and ordering of N atoms; the Fe sublattice remains of ...

Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels' performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano sc...

Plastic pre-strains were applied to the metastable 304L austenitic stainless steel at both room temperature (20 °C) and higher temperatures (i.e., 50, 80 and 100 °C), and then the hydrogen embrittlement (HE) susceptibility of the steel was evaluated by cathodically hydrogen-charging and tensile testing. The 20 °C pre-strain greatly strengthened the steel, but simultaneously significantly increa...