We report on the effects of annealing on the martensitic phase transformation in the Ni-based Heusler system: Mn50Ni40Sn10 and Mn50Ni41Sn9 powder and Co50Ni21Ga32 nanoparticles. For the powdered Mn50Ni40Sn10 and Mn50Ni41Sn9 alloys, structural and magnetic measurements reveal that post-annealing decreases the martensitic transformation temperatures and increases the transition hysteresis. This m...

Feloo-xNi, alloys for x<34 at% i.e., up to the structurally stable Invar concentration, undergo a martensitic transformation. In the parent fcc-phase these alloys show a volume enhancement which is known as the anti-Invar effect. This effect disappears at a concentration at which the martensitic transformation also no longer takes place. In a narrow concentration range of about 301x<34 at% Inva...

We have recently constructed a phenomenological theory that provides a unified explanation for athermal and isothermal martensitic transformation processes. On the basis of this theory, we predict some properties of martensitic transformation and confirm them experimentally using some Fe-based alloys and a Ni-Co-Mn-In magnetic shape memory alloy.

The shape memory effect and superelasticity are usually found in alloys exhibiting spontaneous martensitic transformation. Thus it is hard to imagine that such interesting effects can appear in a system without a martensitic transformation. In this Letter we show shape memory and the superelasticity effect in a nonmartensitic Ti48.5Ni51.5 alloy, which has no martensitic transformation but under...

The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cycli...

A phenomenological description of martensitic transformation is proposed on the basis of such parameters as: a degree of lattice coherency between austenite and martensite phases, mobility of interphase boundaries, elastic energy stored during martensitic transformation and degree of its relaxation. Son),: experimental results confirming the proposed ideas are presented.

The effect of training and predeformation on the martensitic transformation is investigated. It is concluded that Ms as a function of predeformation strain must have a maximum at around 3% strain. Prestrains less than 5% will enhance the martensitic transformation whereas larger prestrains depress it due to strain hardening of the y phase.

Analysis of the dynamic evolution of multilevel structure during martensitic transformations provides kinetics-based constitutive relations for transformation plasticity. Application in numerical modeling of ductile fracture by microvoid-softening-induced shear localization, in conjunction with metallographic study of crack-tip processes, identifies transformation toughening mechanisms operatin...

The displacive transformation classification proposed at ICOMAT 79 [I] is reviewed in light of recent progress in mechanistic understanding. Issues considered include distinctions between shuffle transformation vs. self-accommodating shear, dilatation vs. shear-dominant transformation, and nucleated vs. continuous transformation. 1. HISTORICAL INTRODUCTION Cohen, Olson and Clapp (COC) at ICOMAT...

Cryogenic treatment can be used as a supplemental treatment that is performed on some tool steels between quenching and tempering as an effective method for decreasing retained austenite and increasing wear resistance. In this research, the effect of deep cryogenic treatment (DCT) on dimensional stability and mechanical properties of 80CrMo12 5 tool steel was investigated. The martensitic trans...