Experimental and Crystal Plasticity Investigations of Initial Stress in Thermally Treated Titanium and Nickel Alloys

Abstract

A crystal plasticity model for hcp crystals has been developed which takes due account of the anisotropy which is known to exist in the thermal expansivity. The c-axis expansivity is generally thought to be lower than that for the a-directions and on cooling of a polycrystal (in processing, for example), this potentially leads to the establishment of type II strains and initial stresses which therefore exist prior to in-service loading. Figure 1 below shows a schematic of a model hcp polycrystal in which the crystallographic orientations may be specified within our crystal plasticity finite element formulation (Dunne et al, 2007).