Modeling the Precipitation Processes and Strengthening Mechanisms in a Mg-Al-(Zn) AZ91 Alloy

Author： Hutchinson C.R. Nie J.F. Gorsse S.

ISSN： 1543-1940

Source： Metallurgical and Materials Transactions A, Vol.36, Iss.8, 2005-08, pp. : 2093-2105

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Abstract

A model is developed that couples a description of the continuous precipitation of β-Mg₁₇Al₁₂ laths at elevated temperatures to a summation of the different contributions to the room-temperature 0.2 pct proof strength in the commercial alloy AZ91 (Mg-9Al-1Zn (wt pct)). The central assumptions are the diffusion-controlled formation of shear resistant β-Mg₁₇Al₁₂ laths on the basal planes of the hcp matrix and basal slip as the dominant room-temperature deformation mode. The calculations show quantitative agreement with the evolution of both the reported precipitation kinetics and the strengthening response as a function of aging time at 200 °C. The magnitudes of the different contributions to the hardening are discussed and strategies for enhancing this response are suggested.