A finite element model coupled with a thermokinetic model is developed to predict the phase transformation of the laser deposition of AISI 4140 on a substrate with the same material. Four different deposition patterns, long-bead, short-bead, spiral-in, and spiral-out, are used to cover a similar area. Using a finite element model, the temperature history of the laser powder deposition (LPD) pro...

Kinetic dependence of martensitic transformation and properties changes in Fe-24%Ni5%Mo alloys with different carbon content have been obtained. Internal friction method was used for the precise investigation of structural changes after austenization, during martensitic transformation at sub zero temperature and during the postheat. The influence: (i) of frequency of oscillations, (ii) rate of ...

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...

We provide an extended Peierls–Nabarro (P–N) formulation with a sinusoidal series representation of generalized stacking fault energy (GSFE) to establish flow stress in a Ni2FeGa shape memory alloy. The resultant martensite structure in Ni2FeGa is L10 tetragonal. The atomistic simulations allowed determination of the GSFE landscapes for the (111) slip plane and 2 1⁄2 101 ; 2 1⁄2 110 ; 6 1⁄2 211...

Shape-memory hacks were fabricated in a single processing step ("one-time procedure") by a combination of tensile and bending deformation of a martensitic NiTi-wire. The hacks reversibly changed curvature on heating and cooling in a reproducible manner over 50 thermal cycles. This new type of intrinsic two-way shape memory effect was studied by subjecting the hacks to a beam of high-energy sync...

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...

Phase transformation temperature is one of the most important parameters for the shape memory alloys (SMAs). The most popular method to determine these phase transformation temperatures is the Differential Scanning Calorimeter (DSC), but due to the limitation of the DSC testing itself, it made it difficult for the finished product which is not in the powder form. A novel method which uses the U...

The influence of the free surface on martensitic transformation was examined by comparing the highest temperature at which martensite forms (MS), as measured using dilatometry, with surface–observations using confocal laser scanning microscopy. It is found that the proximity of the surface during confocal microscopy permits martensitic transformation to occur at a higher temperature, with a red...

A significant variant selection is reported in isothermal martensite formed on the surface of an Fe-30% Ni sample. The selection phenomenon is modelled using different descriptions of the martensitic phase transformation. In particular, matrices based on the phenomenological theory of martensite crystallography, the Jaswon and Wheeler distortion, and the continuous face centred cubic-body centr...

Based on the results that the magnitude of the stabilization of retained austenite increases with increasing the amount of martensite transformed, it has been assumed that the martensitic transformation is accompanied with an increase in internal resisting stress which subsequently results in the stabilization of retained austenite. By simplifying this internal resisting stress to be a type of ...