Hot deformation and processing maps of as-sintered CNT/Al-Cu composites fabricated by flake powder metallurgy
(1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. College of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;
3. School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China)
2. College of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;
3. School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China)
Abstract: The deformation behaviors of as-sintered CNT/Al-Cu composites were investigated by isothermal compression tests performed in the temperature range of 300-550 °C and strain rate range of 0.001-10 s-1 with Gleeble 3500 thermal simulator system. Processing maps based on dynamic material model (DMM) were established at strains of 0.1-0.6, and microstructures before and after hot deformation were characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and high-resolution transmission electron microscopy (HRTEM). The results show that the strain has a significant influence on the processing maps, and the optimum processing domains are at temperatures of 375-425 °C with strain rates of 0.4-10 s-1 and at 525-550 °C with 0.02-10 s-1 when the strain is 0.6. An inhomogeneous distribution of large particles, as well as a high density of tangled dislocations, dislocation walls, and some sub-grains appears at low deformation temperatures and strain rates, which correspond to the instability domain. A homogeneous distribution of fine particles and dynamic recrystallization generates when the composites are deformed at 400 and 550 °C under a strain rate of 10 s-1, which correspond to the stability domains.
Key words: CNT/Al-Cu composites; flow stress; processing map; dynamic recrystallization