187. development of fe-ni-co-al-based superelastic alloys
Research Institute Affiliation: Graduate Program in Materials Science and Engineering
Faculty Advisor(s): Kenneth S. Vecchio
Name: Cheng Zhang
Grad Year: 2017
To achieve superelasticity in Fe-base superelastic alloys, a certain combination of matrix strength, precipitation hardening, and microstructural texturing is required. High throughput CALPHAD methods are employed here to examine composition space in NCAXB-type Fe alloys. In Fe-Ni-Co-Al-X-B (X= Ta, Cr, Nb, V, or W) superelastic alloys, the gamma prime ((Fe, Co, Ni)3(Al, X)) phase is available for precipitation strengthening through aging. The hardness of Fe-Ni-Co-Al-X-B alloys was measured after aging at different temperatures for various times. The tensile test results showed that the strength of the gamma matrix affects the stress-induced martensitic (SIM) transformation. XRD results showed that the value of tetragonality (c/a) also has an effect on the SIM transformation. Meanwhile, the coherency relationship between gamma prime nano-sized particles and the gamma matrix was investigated in this research to elucidate its effect on SIM. The Clausius-Clapeyron relationship in the current alloys will also be discussed.
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