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...

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...

An infinite class of counterexamples is given to a conjecture of Dahme et al. [Discuss. Math. Graph Theory, 24 (2004) 423–430.] concerning the minimum size of a dominating vertex set that contains at least a prescribed proportion of the neighbors of each vertex not belonging to the set.

In this paper we present a walking pattern filter for Shape Memory Alloy (SMA) actuated biped robots. SMAs are known for their slow response. The actuation speed limitation can potentially lead to stability problems for biped robots. This filter adapts the human motion for a SMA biped in order to have a stable walking pattern. The Zero Moment Point (ZMP) is used as a main criterion of the filte...

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...