Influence of heat treatment on the properties of the consolidated AZ91D Mg alloy chips was performed in this study. The chips were pressed into a die to form a compact with a green density of 1.6g/cm(3). The 50-mm diameter green compact was then extruded into a 20-mm rod at 350 degrees C. The extruded rod was solution treated at a temperature of 415 degrees C for 24 h; the solution treated specimens were then aged at two temperatures: 170 and 215 degrees C. Heat treatments were conducted to explore the microstructure evolution and mechanical properties of the extruded rod. Heat treatments revealed that the age hardening effect was related to the transformation of the microstructure. Over aging during age heat treatment was believed to be caused by the formation of a lamellar structure composed of alternating layers Of Mg17Al12 phase and magnesium matrix. (c) 2008 Elsevier B.V. All rights reserved.