Papers by Author: Man Jin

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Authors: Jing Li, Zhen Ming Lin, Heng Hua Zhang, Man Jin
Abstract: In order to eliminating the banded structure in SAE8620H gear steel,an isothermal annealing process and its mechanism has been studied in this paper. Results showed that isothermal annealing process can effectively eliminate banded structure in SAE8620H gear steel.With isothermal temperature 640°C-a certain low temperature indeed high undercooling,and for high nucleation at this temperature resulting in the decrease of nucleation rate difference in all areas,banded structure level decreased to 1 level.When isothermal temperature decreased to 610°C and 590°C,although the undercooling is so high that various regions began to nucleate at the same time,the transition temperature is so low that alloy elements in the regions previously occupied by pearlite bands diffuse faster than other regions,thus proeutectoid ferrite grains in these regions grow faster,regenerating the banded structure .
Authors: Man Jin, Jing Li, Guang Jie Shao
Abstract: The precipitation behaviors and microstructures of nano-precipitates in AA6082 Al-Mg-Si alloy with and without Cu additions during heat treatment process were studied using hardness measurements, TEM, mechanical tests and 3DAP. Meanwhile, the softening process of 6082 alloys with Cu and without Cu, isothermally conditioned at 250°C, has also been investigated. It was found that the rate of age hardening, mechanical properties and thermal stability are higher for the Cu-containing alloy. The TEM and 3DAP observations showed that Q’ precipitates were existed after aged at 170°C for 8h in the alloy with Cu addition. Comparing the hardness, mechanical properties and thermal stability curves, it was concluded that the Q’ precipitates play a major role in improving the age hardening kinetics and properties of 6082 alloy with Cu addition.
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