Microstructural Evolution of Semisolid 6063 Aluminum Alloy Prepared by Recrystallization and Partial Melting Process
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JMEPEG DOI: 10.1007/s11665-017-2854-9
Microstructural Evolution of Semisolid 6063 Aluminum Alloy Prepared by Recrystallization and Partial Melting Process Yongfei Wang, Shengdun Zhao, and Chenyang Zhang (Submitted December 31, 2015; in revised form June 16, 2017) Radial forging (RF) was proposed as a novel deformation method to prepare semisolid 6063 aluminum alloy in the recrystallization and partial melting (RAP) process. The effects of area reduction rate, isothermal holding temperature and time on the microstructural evolution of RF-deformed 6063 aluminum alloy were investigated. Results showed that RF can be successfully introduced in RAP process to prepare large semisolid 6063 aluminum alloy bar. With the increase of the area reduction rate, the average grain size firstly decreased and then no significant change occurred. Meanwhile, the spheroidization degree of solid grains firstly increased rapidly, and then increased slowly. The effects of isothermal holding temperature and time are similar, with the increase of the isothermal holding temperature or time, the average grain size initially decreased but then increased; and the spheroidization degree of solid grains gradually increased. High-quality semisolid 6063 aluminum alloy can be prepared with 70% area reduction rate and subsequent semisolid isothermal treatment (SSIT) at 630 °C for 10 min. The coarsening rate constant was 5185.2 lm3/s at 630 °C. Additionally, a strong deformation texture was created in the RF-deformed alloy with 70% area reduction rate, which was transformed to a weakened texture following the SSIT process. Keywords
aluminum alloy, microstructure, radial forging, RAP, semisolid
1. Introduction Semisolid metal forming is a newly developed technology, which requires that the forming materials should be composed of fine spherical microstructure (Ref 1-6). Currently, many methods have been reported to prepare semisolid materials, such as mechanical stirring (Ref 7), electromagnetic stirring (Ref 8-10), cooling slope casting (Ref 11), spray deposition (Ref 12), strain-induced melt activation (SIMA) (Ref 13) and recrystallization and partial melting (RAP) (Ref 14). Among these methods, SIMA and RAP processes are both promising techniques due to their simplicity and low cost (Ref 5, 15, 16). SIMA and RAP processes are similar, mainly including deformation step and semisolid isothermal treatment (SSIT) step. The difference between SIMA and RAP can be described as follows. SIMA involves the hot deformation of starting material above its recrystallization temperature and the cold deformation of the hot deformed material before reheating. While RAP involves only warm deformation of starting material below its recrystallization temperature before reheating, no hot deformation step is required. For both SIMA and RAP methods, the deformation step is a crucial factor and has attracted much attention. Saklakoglu et al. (Ref 17) investigated the effects of compressive
Yongfei Wang, Shengdun Zhao, and Chenyang Zhang, School of Mechanical Engineering, Xi
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