Creep of a thixoformed and heat treated AZ91 Mg-Al-Zn alloy
The most frequently used cast magnesium alloy is AZ91, which contains 9% Al, 1% Zn and some Mn. Recently some studies have investigated the creep response of AZ91 ingots, pressure-die-casting and thixoformed specimens; die-cast and thixoformed alloys frequently show a similar microstructure, with equiaxed grains of {alpha} phase (solid solution of Al and Zn in Mg) and a brittle secondary phase, Mg{sub 17}Al{sub 12} ({beta} phase), on grain boundaries. The die-cast alloy has a very fine grain size (15 {micro}m) and a higher concentration of Mg{sub 17}Al{sub 12} than ingots; the thixoformed alloy exhibits large {alpha} phase globules of around 100 {micro}m and small {alpha}-particles of few microns in the eutectic region. The creep response of the die-cast and thixoformed alloys was found to be substantially equivalent, the creep strength of the die-cast material being one order of magnitude lower than that of the ingot. Thixoforming is one of the new processes that can be used to produce Magnesium alloy components for automotive applications. However, the typical structure of the thixoformed AZ91 exhibits a modest ductility, a property that can be substantially improved by subsequent solution treatment aimed at dissolving the brittle {beta} phase. The present study was undertaken to investigate the high-temperature response of thixoformed and solution treated AZ91.
- Research Organization:
- Univ. of Ancona (IT)
- OSTI ID:
- 20015216
- Journal Information:
- Scripta Materialia, Vol. 42, Issue 4; Other Information: PBD: 31 Jan 2000; ISSN 1359-6462
- Country of Publication:
- United States
- Language:
- English
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