期刊
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
卷 399, 期 1-2, 页码 181-189出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2005.03.009
关键词
impact toughness; hypereutectic Al-Si alloy; rotary-die equal-channel angular pressing (RD-ECAP) ultrafine-grained microstructures; ductile fracture
The impact toughness of a hypereutectic Al-23 mass% Si alloy was improved by rotary-die equal-channel angular pressing (RD-ECAP). The alloy was successfully processed by RD-ECAP at high temperatures of 673 K and 623 K. The absorbed energy as measured by Charpy impact tests significantly increased with increasing the number of RD-ECAP passes, and finally reached 13.0 kJ/m(2) after 32 passes. This value is 18 times higher than that of the as-cast Al-23 mass% Si alloy and 41% higher than that of the as-cast eutectic Al-11 mass% Si alloy. The grain or grain fragment size is about 150 nm. In addition, most of the large primary silicon particles (over 50 mu m) were broken in the first 4 passes, and the primary silicon particle sizes decreased with increasing the pressing passes. These results indicate that the multipass RD-ECAP is effective in improving impact toughness through refining grains and changing the primary silicon particles. On the other hand, many voids were produced in the first 4 passes. These voids, however, were gradually eliminated with increasing the pressing passes, and finally only a few small voids were observed after 32 passes. The RD-ECAP processed Al-23 mass% Si alloy therefore showed ductile fracture during the impact testing. (c) 2005 Elsevier B.V. All rights reserved.
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