Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn(2)NiGa and Mn(1+x)Ni(2-x)Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn(2)NiGa is ferrimagnetic and its total spin moment increases when di...

Morrison, Keith R. M.S.M.S.E., Purdue University, August 2014. Nickel Aluminum Shape Memory Alloys via Molecular Dynamics. Major Professor: Alejandro Strachan. Shape memory materials are an important class of active materials with a wide range of applications in the aerospace, biomedical, and automobile industries. These materials exhibit the two unique properties of shape memory and superelast...

In order to gain a better understanding of the formation of plessite in iron meteorites, various electron optical techniques were employed to study the range of plessite structures observed in the Carlton fine octahedrite. Compositional and structural studies of twins in clear taenite and the cloudy zone were made. Transmission electron microscopy studies of martensitic and duplex a + y plessit...

The damping characteristics of Ti50Ni50-xCux (x = 0~30 at.%) shape memory alloys (SMAs) at a low frequency have been studied using a dynamic mechanical analyzer. The magnitude of the tan δ value and the values of the storage modulus (E₀) softening/hardening and the strain variation exhibited in B2↔B19 transformation are all higher than those in B2↔B19' transformation. The larger E₀ softening/ha...

The microstructure and properties of a 5 wt.% Cr cold work tool steel were studied after austenitisation at 1020°C, 1050°C or 1075°C followed by single, double and triple tempering treatments at 525°C. The microstructures were investigated with scanning electron microscopy and X-ray diffraction and phase transformations were studied by dilatometry. Furthermore, hardness and Charpy un-notched an...

Deformation-induced martensites generally follow the principle on selection of their variants in intrinsic crystallographic orientations with regard to parent grains, which should be significantly affected by cooperative rotation matrix. In this paper, microstructural changes related deformation-induced transformation from metastable γ austenite ε and α′ 304 austenitic stainless steel upon unia...

Deformation-induced martensitic transformation as the basis of a hardening process is dependent, among others, on stress state. In applications such cryogenic cutting, where hardened subsurface can be produced in metastable austenitic steels, different states exist. Furthermore, cutting typically occurs at high strain rates greater than 103s?1. order to gain deeper insight into behavior steel (...

In this paper, the effects of carbon, Si, Cr and Mn partitioning on ferrite hardening were studied in detail using a medium Si low alloy grade 35CHGSA steel under ferrite-martensite/ferrite-pearlite dual-phase (DP) condition. The experimental results illustrated that an abnormal trend had occurred with progress formation. At first, microhardness decreased increasing volume fraction ferrite, the...

Hydrogen embrittlement can occur in steels with metastable phases, due to activation of the hydrogen-enhanced decohesion mechanism upon transformation. Meanwhile, recent investigations suggest that alloys undergoing ε-martensite transformation may exhibit resistance hydrogen embrittlement. To better understand effects these alloys, we investigate hydrogen-induced microstructural transformations...