Effect of Orientation and Temperature on the Mechanical Properties of Commercially Pure Titanium

This paper investigates the changes in deformation mechanisms of commercially pure titanium over a range of temperatures for different orientations relative to the initial rolling texture. Samples from grade 1 titanium plate were tested in plane strain compression (PSC). Extremes of orientation relative to the predominant split basal texture were tested at temperatures from 25 degrees C to 700 degrees C. Specimens were subsequently examined using X-ray texture analysis and electron back-scatter diffraction (EBSD). Changing the orientation resulted in substantial yield stress anisotropy. This was found to be largely related to the orientation of the dominant texture relative to the most favorable orientation for the easiest slip mode (prism slip), and significantly but to a lesser extent on differences in twinning behaviour. The most important difference in twinning was the operation of {10 (1) over bar2} tensile twinning in c-axis tension and {11 (2) over bar2} compression twinning in c-axis extension. Calculations indicated that at low temperature both of these twinning modes accommodate a significant amount of strain. Twinning was also found to be the most significant factor affecting work hardening behaviour, with reorientation hardening occurring for some sample orientations. As temperature was increased above similar to 350 degrees C {10 (1) over bar1} twinning became the dominant twinning mode, but its contribution to the strain was not as large as the low temperature twinning modes, and the total amount of twinning decreased with temperature. The decrease in twinning with increasing temperature led to a reduction in the difference in work hardening behaviour. The quantitative information gathered in the course of this work is discussed in the context of mechanical property prediction.