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Abstract: The hot deformation behavior of Zn82.7–Al10.2–Cu2.1 (in wt.%) was investigated by means of hot compression tests in the temperature range of 180–330°C and strain rate range of 0.01–10s−1. Processing maps were developed on the basis of experimental data and using the principles of the dynamic materials model (DMM). The results show that the maximum stress decreases with decreasing strain rate and increasing temperature, and that the activation energy is about 141.895kJ/mol. It is found that the strain has insignificant effect on the power dissipation maps. The maps exhibit two domains. The first domain occurs in the temperature range of 218–270°C and strain rate range of 0.04–1.2s−1 with the peak efficiency of 0.53. The second domain occurs in the temperature range of 290–330°C and strain rate range of 0.01–0.18s−1 with the peak efficiency of 0.58. Microstructural observations reveal that the partial dynamic recrystallization (DRX) of the Zn-rich phase occurs in the first domain and the full DRX of that occurs in the second domain. The dendritic structure is partially fragmented and elongated within the eutectic matrix and some initial laminar Al-rich phase is transformed into a spherical shape in the two domains. The large regime of flow instability is observed at the higher strain rates and all the tested temperatures with strain higher than 0.3. It expands when strain is increased. The flow instability predicted by processing maps is manifested as adiabatic shear bands, micro-cracks and macro-shear cracks. [Copyright &y& Elsevier]

Abstract: The hot deformation behavior of Inconel 690 has been investigated by means of hot compression tests in the temperature range of 950–1200°C and strain rate range of 0.001–10s−1. The results show that the maximum stress decreases with decreasing strain rate and increasing temperature, and the activation energy is about 380.215kJ/mol. Processing maps developed on the basis of experimental data and using the principles of the dynamic materials model exhibited two domains. The first domain occurs in the temperature range of 970–1120°C and strain rate range of 0.03–3.3s−1, with a peak efficiency of power dissipation of 0.39. The second domain occurs in the temperature range of 1150–1200°C and strain rate range of 0.003–0.1s−1, with a peak efficiency of power dissipation of about 0.37. Microstructural observations revealed that the full dynamic recrystallization (DRX) occurred in these two domains. In the first domain, the undissolved carbides assisted in nucleating DRX and restricted the coarsening of the full DRX grains and the refined grains were obtained. A small regime of flow instability was noticed at low temperature and high strain rate. [Copyright &y& Elsevier]

Abstract: Hot compressions tests of Inconel 625 superalloy were conducted using a Gleeble-1500 simulator at different strains between 900°C and 1200°C with a strain rate of 0.1s−1. Optical microscope, transmission electron microscope and electron backscatter diffraction technique were employed to investigate the microstructure evolution and nucleation mechanisms of dynamic recrystallization. It was found that both the size and fraction of dynamically recrystallized grains increase with increasing deformation temperature. However, the size of dynamically recrystallized grains almost remains constant with increasing deformation strain. The dominant nucleation mechanism of dynamic recrystallization in Inconel 625 superalloy deformed at 1150°C is the discontinuous dynamic recrystallization, which is characterized by the bulging of the original grain boundaries accompanied with twining. The continuous dynamic recrystallization characterized by progressive subgrain rotation occurs simultaneously in dynamic recrystallization process, although it can only be considered as an assistant nucleation mechanism at the early stage of hot deformation. [Copyright &y& Elsevier]