Microstructural evolution during reheating of A356 machining chips at semisolid state

• Published in: International journal of minerals, metallurgy and materials Vol. 24; no. 8; pp. 891 - 900
• Main Authors: Wang, Fang, Zhang, Wen-qiang, Xiao, Wen-long, Yamagata, Hiroshi, Ma, Chao-li
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01.08.2017; Springer Nature B.V; Key Laboratory of Aerospace Advanced Materials and Performance of the Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191, China%Center for Advanced Die Engineering and Technology, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Corrosion and Coatings; Diamond pyramid hardness; Evolution; Glass; Grain size; Heat treating; Heating; Machining; Materials Science; Metallic Materials; Natural Materials; Particle size; Recrystallization; Semi-solid processing; Semisolids; Shape factor; Slurries; Surfaces and Interfaces; Temperature; Thin Films; Tribology; aluminum chips; microhardness; semisolid slurry; microstructural evolution; grain coarsening
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-017-1475-5

The microstructural evolution of A356 machining chips in the semisolid state was studied at different temperatures and holding times. The results showed that the elongated α-Al grains first recrystallized in the semisolid state and then became globular with a high shape factor（SF）. Both the temperature and the holding time clearly affected the grain size and SF. When the heating temperature or holding time was increased, the grain size and SF gradually increased and finally became stable. Moreover, the Vickers hardness of primary α-Al grains gradually decreased with increasing heating temperature. The optimal slurry for semisolid processing, with a good combination of grain size and SF, was obtained when the chips were held at 600℃ for 15 min. The semisolid slurry of A356 chips exhibited a lower coarsening rate of α-Al grains than those produced by most of the conventional semisolid processes. The coarsening coefficient was determined to be 436 μm3·s-1 on the basis of the linear Lifshitz–Slyozov–Wagner（LSW） relationship.