Experimental Study of the Transformation-Induced Plasticity in a Cr-Ni-Mo-Al-Ti Steel

Abstract

Abstract. This paper shows cxpcrinicn~~~l results concerning thc lnartcnsitic transcormation and the transfor1nation-in(i~1cc(I plasticity undcr multinsial loading. The matcrial investigated is a Cr-Ni-Mo-Al-Ti steel, which is suhrnitlcd to :I y--)cr.' nlartcnsitic phasc: transformation undcr an applicd strcss. The specimens are thin tubes loadcd in ~cnsion-~orsion. The ~csts wcrc specially dcsigncd to providc information on classical questions rclatcd with transforrna~ion plasricily and 111c ~ntcraction bctwccn applicd strcsscs and phasc transSormations in the casc of tcnsion-shear loadings: cl'fcct of the applicti strcsscs on M, tcmpcrature, definition of the transformation-ind~~ccci p l ; ) s~i c~~y (Ilow intensity, dirwtion in sucss spacc, evolution vs phase change), eventual prcsencc of inicrr~iil strcsscs. Somc ol' the answers gi\fcr~ by thc prcscnt study confirm the usual assumptions, but the analysis of the tcsts also rcvculs ncw cfkcts not predicted by thc classical theories proposed to quantify the transformation induccd plastici~y phcnomcnon.

Unified Constitutive Equations for Phase Transformation and Thermoplasticity

“…The term represents the orientation effect (Marketz and Fischer, 1995). Even in the case the trip strain progresses, which agrees with the experimental observation by Videau et al (1996).…”

Pre-deformation–transformation plasticity relationship during martensitic transformation

“…Similar to the effect of an increase in stress levels superimposed during the phase transformation, previous studies have shown that an increase in pre-strain levels prior to isothermal bainitic reactions also result in significant TP strains [1,12]. Since the occurrence of TP strains is attributed to the occurrence of external stresses superimposed during the phase transformation, transformations plasticity strains prevalent after pre-straining the specimens mostly stem from residual stress fields generated during pre-straining [32]. Since an anisotropic shape change occurs, the stress fields around the introduced dislocations seem to have a preferred alignment.…”

“…However, plastic pre-deformations with more than 10% strain tend to retard the transformation as the forming phase fronts start hindering each other [14]. In addition, TP strains were associated with the residual stresses brought about by plastic pre-deformations [32], and were different under the simultaneous application of pre-deformation and superimposed stresses below the elastic limit [19]. Thus, TP, a key parameter in the modelling of bainitic and martensitic phase transformations, deserves further investigation to uncover the roles of and the interrelationship between the governing mechanisms.…”

Prediction of residual stress and distortion of ferrous and non-ferrous metals: Current status and future developments

“…They rest on the hypothesis that only the first mechanism mentioned above operates. For martensitic transformation, more recent experimental work [40] concluded that this assumption is reasonable within a first approximation, but the model must be refined. Nevertheless, formulation of a macroscopic law for martensitic transformation plasticity in ferrous alloys is still an open question even if micromechanical models have seen outstanding developments.…”