|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Characterization of Minerals, Metals, and Materials
||Composition Dependent Martensitic Transformation and Softening of Elastic Constants
||Le Zhou, Abhishek Mehta, Anit Giri, Kyu Cho, Yongho Sohn
|On-Site Speaker (Planned)
Martensitic transformation is commonly observed in ordered alloys where austenitic phase diffusionlessly transforms to martensitic phase. In this study, solid-to-solid diffusion couples in binary Ni-Al and ternary Ni-Mn-Ga systems were annealed and analyzed by SEM, TEM and nanoindentation to examine the martensitic transformation of β-NiAl (B2) and Ni2MnGa (L12) upon cooling to room temperature. Composition variation created during diffusion anneals yielded composition-dependent transformation where one side transformed to martensite and the other retained the high temperature phase. In both alloy systems, composition dependent reduced elastic modulus and hardness were obtained. A minimum value near the austenite/martensite interphase boundary was consistently observed, which can be explained by softening of the elastic constants (i.e., lattice softening) prior to the martensitic transformation. Microscopic and nano-indentation results are presented with respect to the compositional changes and composition-dependent martensitic transformation, and their significance is discussed for shape memory alloys and high temperature alloys.
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