New Intrinsic Mechanism on Gum-Like Superelasticity of Multifunctional Alloys


Ti-Nb-based Gum Metals exhibit extraordinary superelasticity with ultralow elastic modulus, superior strength and ductility, and a peculiar dislocation-free deformation behavior, most of which challenge existing theories of crystal strength. Additionally, this kind of alloys actually displays even more anomalous mechanical properties, such as the non-linear superelastic behavior, accompanied by a pronounced tension-to-compression asymmetry, and large ductility with a low Poisson's ratio. Two main contradictory arguments exist concerning the deformation mechanisms of those alloys, i.e., formation of reversible nanodisturbance and reversible martensitic transformation. Herein we used the in-situ synchrotron high-energy X-ray scattering technique to reveal the novel intrinsic physical origin of all anomalous mechanical properties of the Ti-24Nb-4Zr-8Sn-0.10O alloy, a typical gum-like metal. Our experiments provide direct evidence on two different kinds of interesting, stress-induced, reversible nanoscale martensitic transitions, i.e., the austenitic regions with B2 structure transform to α" martensite and those with BCC structure transform to ō martensite.



Crystals, Alloys, Superelasticity, Deformations (Mechanics), Photons

"This study was supported by the National Basic Research Program of China (973 Program) (Grant No.s 2012CB619405, 2012CB933901 and 2012CB619103), the National Natural Science Foundation of China (Grant No.s 51231002, 51071152 and 51271180), and the Fundamental Research Funds for the Central Universities (Grant No. 06111020). Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DE-AC02-06CH11357. YW and DW thank the support of the U.S. Natural Science Foundation Grant No. DMR-1008349, National Basic Research Program of China (Grants No. 2012CB619402 and No. 2010CB631003) and National Natural Science Foundation of China (Grants No. 51201125)."


CC BY 3.0 (Attribution), ©2013 The Authors