Why rolled Mg-Al-Ca-Mn alloys are less responsive to aging as compared to the extruded

Abstract

Dilute Mg-Al-Ca-Mn alloys exhibit excellent strength-ductility combinations in the peak-aged condition due to ordered, single atomic layer Guinier-Preston (GP) zones. The present work explains why rolled sheet material is softer and less responsive to aging, as compared to extruded. Using crystal-plasticity modeling, it is shown that the initial texture of the rolled material permits the soft modes, basal slip and twinning, to accommodate more of the strain during in-plane tension, and they are less responsive to hardening by the finely dispersed GP zones. Even with the same number density of GP zones, the extruded material is stronger in tension along the extrusion axis due to an initial texture which forces higher relative activity of prismatic slip, a mode previously shown to be strongly affected by the GP zones. The present work reemphasizes the significant role of the initial texture in determining the strength and anisotropy of non-cubic metals and alloys.