Journal
METALS AND MATERIALS INTERNATIONAL
Volume 25, Issue 2, Pages 372-380Publisher
KOREAN INST METALS MATERIALS
DOI: 10.1007/s12540-018-0204-6
Keywords
AZ91; Flake; Rapid solidification; Extrusion; Recrystallization
Funding
- National Research Foundation of Korea (NRF) - Korean government (MSIP, South Korea) [2016R1C1B2012140, 2018R1C1B6002068]
- National Research Foundation of Korea [2016R1C1B2012140, 2018R1C1B6002068] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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A high-strength AZ91 alloy is produced via hot extrusion using flakes fabricated through the rapidly solidified flaky powder metallurgy. The AZ91 alloy flakes have an extremely fine dendritic structure without any second-phase particles owing to the fast cooling rate during solidification; these microstructural features considerably promote dynamic recrystallization and precipitation behaviors during extrusion process. As a result, the AZ91 alloy extruded using the flakes exhibits an almost fully recrystallized microstructure with a very small average grain size of 1.2 mu m owing to an increase in the number of nucleation sites for recrystallization, and it shows a high microstructural homogeneity owing to the numerous Mg17Al12 precipitates uniformly distributed throughout the material. This extruded AZ91 alloy has a tensile yield strength of 345MPa, ultimate tensile strength of 417MPa, and total elongation of 5.6%. These superior tensile strengths are mainly attributed to the combined effects of precipitation hardening caused by abundant fine precipitates and grain boundary hardening caused by fine recrystallized grains.
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