Structural evolution and the Hall-Petch relationship in an Al-Mg-Li-Zr alloy with ultra-fine grain size
- Fukuoka Univ. of Education, Munakata, Fukuoka (Japan). Dept. of Technology
- Kyushu Univ., Fukuoka (Japan). Dept. of Materials Science and Engineering
- Ufa State Petroleum Technical Univ. (Russian Federation). Inst. of Chemical Technology
- Ufa State Aviation Technical Univ. (Russian Federation). Inst. of Physics of Advanced Materials
- Univ. of Southern California, Los Angeles, CA (United States)
Experiments were conducted on an Al-5.5% Mg-2.2% Li-0.12% Zr alloy to investigate the feasibility of introducing an ultra-fine grain size using equal-channel angular (ECA) pressing and of retaining an ultra-fine grain size at elevated temperatures. It is shown that ECA pressing is capable of reducing the grain size from an initial value of {approximately}400 {micro}m to a value of {approximately}1.2 {micro}m. However, the microstructure after ECA pressing is heterogeneous, with many areas of equiaxed grains having high angle grain boundaries and some regions of subgrains with boundaries having low angles of misorientation. Unlike earlier experiments on Al-Mg binary alloys, it is demonstrated that the grain size of the Al-Mg-Li-Zr alloy is reasonably stable up to temperatures as high as {approximately}700 K because of the presence in the matrix of a fine dispersion of {beta}{prime}-Al{sub 3}Zr precipitates. Microhardness data confirm the Hall-Petch relationship for grain sizes above {approximately}2 {micro}m produced by annealing at temperatures above {approximately}673 K, but the Hall-Petch relationship breaks down at smaller grain sizes because of variations in the volume fraction of the {delta}{prime}-Al{sub 3}Li precipitates.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 590024
- Journal Information:
- Acta Materialia, Vol. 45, Issue 11; Other Information: PBD: Nov 1997
- Country of Publication:
- United States
- Language:
- English
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