Stability of the Reversible Martensite Transformation in Ni-35 at % Al
University of Twente, Faculty of Mech. Eng., Materials Science and Engineering Group, P.O. Box 217, 7500 AE Enschede, The Netherlands
The stability of the martensitic transformation in Ni-35at% Al was investigated as a function of processing and heat treatment conditions. Material was produced by HIPing or sintering of as-received, attritor milled or ball-milled powder. A reversible martensitic transformation is obtained in mechanically milled and consolidated Ni-35at% Al Whereas Ni5Al3 suppresses the martensitic transformation in the material made from as-received powder, the Ni5Al3 transformation from the L10 martensite itself is retarded by the formation of Ni2Al in the mechanically milled material.. This could be explained by the fine grain size and microstructural disorder. The activation energy for short range order is lowered, thereby facilitating the formation of Ni2Al and the martensitic transformation. The present results are promising for the further development of NiAl and its alloys as high temperature shape memory alloys.
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