Papers by Author: Hasani Chauke

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Authors: Hasani Chauke, Mordecai Mashamaite, Rosinah Modiba, Phuti Ngoepe
Abstract: In this study, we investigate the effect of ternary addition on the structural, mechanical properties and temperature dependence of Ti-based as potential shape memory alloys using molecular dynamics approach. We found that binary Ti-Pt alloys exhibit shape memory properties and display possible martensitic transformation from B2 to B19 phases. Partial addition with Zr, Co, Pd, Ir showed preferential ternary high temperature shape memory alloys formation of 6.25 at. % X composition (Ti-Pt-X). We found that the equilibrium lattice constants are in better agreement with the available experimental values. The heats of formation and elastic properties reveal possible composition and phases at temperature above 900 K with good shape memory properties. Their structures were confirmed using the X-ray diffraction patterns at different temperatures.
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Authors: Rosinah Modiba, Hasani Chauke, Phuti Ngoepe
Abstract: The study on the Ti-based materials and its application has been the interest of many research industries. These alloys are known to have an ordered B2 phase at high temperatures and transform to a stable low B19 martensitic phase. First principle approach has been used to study L10, B32, B2 and B19 Ti50Al50 alloys and the results compared well with the available experimental data. The equilibrium lattice constants are in good agreement with the experimental values (within 3% agreement). Furthermore, the elastic constants of these alloys are calculated, and revealed stability for L10 and B19 structures, while B2 and B32 gave C′<0 (condition of instability).
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Authors: Rosinah Mahlangu, Hasani Chauke, P.E. Ngoepe
Abstract: The supercell approach method was used to investigate the effect of partial substitution of Pt with Co on the TiPt potential shape memory alloy. The first-principles calculations were carried out within the generalized gradient approximation to determine the stability of the Ti50Pt50-xCox for x=6.25, 18.75 and 25. We found that the calculated heats of formation and density of states predicted the 6.25 at. % Co to be the most stable structures compared. The elastic properties, thermal coefficient of linear expansion and the density of states results suggest that the partial substitution of Pt with Co decreases the Ms of TiPt with the softening of the Cʹ shear moduli.
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Authors: M.P. Mashamaite, Hasani Chauke, Rosinah Mahlangu, P.E. Ngoepe
Abstract: Shape memory alloys (SMAs) are a fascinating group of metals that have two remarkable properties, the shape memory effect and superelasticity. The TiPt structure with the B2 phase has been reported to undergo a reversible displacive transformation to B19 martensite at about 1200K. However, this system could serve in principle as the basis of high-temperature shape memory alloys. Molecular dynamics study of martensitic transformation in platinum titanium alloys was performed to investigate the effect of temperature dependence on B2 and B19 structures at 50 at.%Pt. The NPT ensemble was used to determine the properties of these systems and we found good comparisons with recent experimental work. The temperature dependence of TiPt shows potential martensitic change when B19 is heated to extreme high temperatures of 273K up to 1573K.
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