Experimental study of the transformation-induced plasticity in a Cr-Ni-Mo-Al-Ti steel

This paper shows experimental results concerning the martensitic transformation and the transformation-induced plasticity under multiaxial loading. The material investigated is a Cr-Ni-Mo-Al-Ti steel, which is submitted to a γ→α' martensitic phase transformation under an applied stress. The specimens are thin tubes loaded in tension-torsion. The tests were specially designed to provide information on classical questions related with transformation plasticity and the interaction between applied stresses and phase transformations in the case of tension-shear loadings: effect of the applied stresses on Ms temperature, definition of the transformation-induced plasticity (flow intensity, direction in stress space, evolution vs phase change), eventual presence of internal stresses. Some of the answers given by the present study confirm the usual assumptions, but the analysis of the tests also reveals new effects not predicted by the classical theories proposed to quantify the transformation induced plasticity phenomenon. (orig.)