Application to HCP Metals and Alloys

Abstract

Section 3.3 summarized several unique characteristics of slip in hexagonal close-packed (HCP) metals. In particular, the close-packed system-the basal plane (0001) and the close-packed direction < > 1120 -has only three independent systems compared with the 12 available in the face-centered cubic (FCC) crystal structure. Therefore, slip is observed on other crystal planes. The prismatic plane was referred to in Section 3.3. In the Miller-Bravais coordinate system, this is the ( ) 1010 plane and the close-packed direction < > 1120 . Slip is also observed on the pyramidal system, which is ( ) 1011 plane and, once again, the close-packed direction < > 1120 . The ease of slip in HCP metals as influenced by the dislocation energy and the spacing between parallel slip planes (as discussed in Section 3.2 in regard to the Peierls stress) is affected by the active slip system(s). One implication of this is that one should expect less commonality between in deformation kinetics in HCP metals than observed in FCC and body-centered cubic (BCC) metals.In this chapter, the temperature dependence and, in some cases, the strainrate dependence of deformation in pure Cd, Ti, Zn, and Zr and in Mg, Zr, and Ti alloys is examined. The analysis presented in these HCP metals is complicated by (1) the limited availability of extensive experimental campaigns available for model FCC and BCC systems, (2) contributions of deformation twinning observed in most of the HCP systems-particularly at low (homolo-Fundamentals of Strength: Principles, Experiment, and Applications of an Internal State Variable Constitutive Formulation, First Edition. Paul S. Follansbee.