Deformation Characteristics and Constitutive Equations for the Semi-Solid Isothermal Compression of Cold Radial Forged 6063 Aluminium Alloy

Abstract

Al-Mg-Si based alloys are popular alloys used in the automotive industry. However, limited studies have been performed to investigate the microstructure, deformation characteristics, and deformation mechanism for the semi-solid 6063 alloys. In this study, the cold radial forging method and semi-solid isothermal treatment (SSIT) are proposed in the semi-solid isothermal compression (SSIC) process to fabricate high-quality semi-solid 6063 billets. The effects of deformation temperature, strain rate, and strain on the microstructure, deformation characteristics, and deformation mechanism of the SSIC of cold radial forged 6063 alloys were investigated experimentally. Constitutive equations were established based on the measured data in experiments to predict the flow stress. Results show that an average grain size in the range from 59.22 to 73.02 μm and an average shape factor in the range from 071 to 078 can be obtained in the microstructure after the cold radial forged 6063 alloys were treated with SSIT process. Four stages (i.e., sharp increase, decrease, steady state, and slow increase) were observed in the true stress- true strain curve. The correlation coefficient of the constitutive equation was obtained as 0.9796 while the average relative error was 5.01%. The deformation mechanism for SSIC of cold radial forged aluminum alloy 6063 mainly included four modes: The liquid phase flow, grain slide or grain rotation along with the liquid film, slide among solid grains, and the plastic deformation of solid grains.

Semi-Solid Forging Process of Aluminum Alloy Connecting Rods for the Hydrogen Internal Combustion Engine

“…As shown in Figure 6a, the RF-deformed 7075 aluminum alloy blank had four different diameters, indicating the FRs of 30.56%, 42.91%, 52.54%, and 75%, respectively. The value of the FR increases with the decrease in the diameter, which represents an elevation in the strain energy stored in the RF-deformed blank, when the diameter decreases under the RFPD process [52]. As presented in Figure 6b-e, the RF-deformed blanks with different FRs had smooth surfaces without any defects, such as surface cracks or pits, which indicated that the 7075 aluminum alloy with a diameter of 90 mm used in this work can be successfully deformed by the RFPD process, with an FR up to 75%.…”

Hot Deformation and Microstructure Evolution of Metallic Materials

“…Optimum deformation conditions for both states are temperatures from 500 °C to 520 °C, and strain rates ranging from 0.01 s −1 to 0.1 s −1 for the as-cast material as well as a strain rate of 1 s −1 for the TRC material. Wang et al [ 5 ] proposed the cold radial forging method and semi-solid isothermal treatment in the semi-solid isothermal compression (SSIC) process to fabricate high-quality, semi-solid billets of 6063 aluminum alloy. Constitutive equations were established based on the experimental data to predict the flow stress.…”