Transformation conditions in an Fe-based shape memory alloy under tensile-torsional loads: martensite start surface and austenite start/finish planes

Transformation conditions are determined experimentally in Fe-9%Cr-5%Ni-14% Mn-6%Si polycrystalline shape memory alloy in the axial stress-shear stress -temperature space. The martensite start condition is represented by an ova l corn, exhibiting a strong anisotropy, whereas the austenite start/finish conditions are given by the parallel planes, the normal vector of which dep ends on the direction of pre-stressing. The von Mises type condition does n ot fit to the data. The normality condition is almost acceptable. The therm odynamic consideration explains well the results under the condition that o nly one martensite Variant is formed during proportional loading. (C) 1999 Elsevier Science S.A. All rights reserved.