期刊
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
卷 492, 期 1-2, 页码 153-160出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2008.03.007
关键词
creep; magnesium alloys; precipitates
The creep response of commercial Mg-Al alloys for die-casting was described by taking into account the distinctive microstructure consisting of alpha-Mg primary grains and a divorced eutectic formed by supersaturated alpha-Mg and beta-Mg17Al12 typical of these materials. The alpha-Mg grains were assimilated to soft zones in a composite reinforced by hard zones rich in precipitates, the latter being the grain boundary regions of supersaturated alpha-Mg and beta-Mg17Al12. Constitutive equations correlating minimum creep rate, applied stress and temperature were derived for dilute Mg-Al solid solutions and used to calculate the forward stress acting in soft and hard regions, respectively, on the assumption that both creep with a similar strain rate. The role of the particles was then expressed by a threshold stress; as a consequence, Si addition resulted in a Substantial increase in the threshold stress in the hard zones, a mechanism that explains the reduction in minimum creep rate observed in the high-temperature low-stress regime in Mg-Al-Si compared with Mg-Al-Zn alloys. (C) 2008 Elsevier B.V. All rights reserved.
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