Effect of variation of cold-rolling strain-paths on the microstructure, texture and mechanical properties of alloy Ni-16Cr-8Fe

Abstract

In this work, the effect of variation of cold-rolling strain-paths (one-directional (U), two-stage cross (T), and multi-stage cross (M) rolling) on the evolution of microstructure as well as texture and their correlation with mechanical properties of alloy Ni-16Cr-8Fe has been studied. The overall texture strengthens while increasing rolling reductions from 30-to-50 and 50-to-90 % in all the strain-paths. In U strain-path, two of the standard rolling components—copper and brass—are strengthened significantly, while in T and M strain-paths only brass component strengthens. The overall texture has strong relationship with the brass-component of β-fibre irrespective of the strain-paths used during cold-rolling. The strain-path plays an important role in the changeover of texture from metal- to alloy-type, unlike what was previously thought that lowering of alloy’s stacking fault energy is the only reason. The yield (σYS) and tensile (σUTS) strength of 90 % rolled samples are significantly higher in U as compared to T and M strain-paths. The flow curves of 90 % rolled alloy follow Ludwigson-relationship with negative deviation in all the strain-paths. Regardless of the strain-paths, the area of yield locus ellipse increases as the rolling reductions are increased from 30-to-50 and 50-to-90 % and bear a good relationship with the overall texture. The average in-plane anisotropy in yield stress is observed to be highest in U strain-path. The theory of relative resolved shear stress of fcc slip systems in presence of highest intensity texture component well explains the variation in the values of in-plane anisotropies.