Effects of Temperature and Time on Microstructural Evolution of Semisolid 5A06 Aluminum Alloy: Preparation of Semisolid
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JMEPEG https://doi.org/10.1007/s11665-020-04959-8
Effects of Temperature and Time on Microstructural Evolution of Semisolid 5A06 Aluminum Alloy: Preparation of Semisolid Billets in Ellipsoid Solid Phase Jufu Jiang, Yingze Liu, Guanfei Xiao, Ying Wang, and Xinquan Xiao (Submitted May 5, 2020; in revised form June 20, 2020) To shorten the semisolid billet process and reduce its cost, the effects of isothermal temperature and soaking time on the microstructural evolution and coarsening rate during directly heating room temperature hotrolled 5A06 aluminum alloy to semisolid temperature were investigated. Samples cut from the hot-rolled plates were heated to semisolid temperatures ranging from 580 to 620 °C, and soaking for 5-30 min. The microstructure of samples was characterized by optical microscopy, scanning electron microscopy with energy-dispersive x-ray spectroscopy, and Image-Pro Plus software. The results showed that the microstructure contained ellipsoidal solid grains with the quantitative parameters of the average grain size of 143 lm and averaged shape factor of 0.55 under an optimal condition of 615 °C for 20 min. Recrystallization occurred within 5 min of holding time, increasing temperature can promote recrystallization, which is beneficial to spheroidization of solid phase, and it will also accelerate melting and the growth of solid particles. Extending soaking time, the liquid phase increased gradually and the change of solid particles was complicated. Abnormal accumulation of liquid phase was found, which will lead to the formation of irregular structure. The reasonable coarsening rate constants ranged from 1319 to 3454 lm3 s21 under the desired treatment parameters. The segregation of Mg occurred at the grain boundaries, as well as around the inclusions within the grains. Keywords
5A06 aluminum alloy, recrystallization, semisolid
microstructure,
1. Introduction Semisolid processing (SSP) technology is considered to be the most promising metal part forming technology because of its high production efficiency, low deformation resistance, high mold life, near-net-shaped complex parts, high surface quality, and high strength of molded parts (Ref 1-6). Nowadays, the performance of semisolid formed parts is close to forged parts (Ref 7-10). It is worth mentioning that part of the original intention of developing semisolid technology is to solve the waste of raw materials and energy for forming metal parts. However, the current cost of preparing semisolid billets is relatively high, which contradicts some of the advantages of this technology (Ref 11). For the preparation of semisolid billet, the solid-phase route has the advantages of low energy consumption, no pollution to the melt, and no need for special equipment (Ref 2, 11). Typical solid-phase semisolid billet preparation methods are straininduced melting activation (SIMA) (Ref 12) method and
Jufu Jiang, Yingze Liu, Guanfei Xiao, and Xinquan Xiao, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PeopleÕs Re
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