Effect of Grain Size Inhomogeneity of Ingot on Dynamic Softening Behavior and Processing Map of Al-8Zn-2Mg-2Cu alloy
- Resource Type
- Article
- Authors
- Di Feng; Guoying Wang; Hongmei Chen; XinMing Zhang
- Source
- Metals and Materials International, 24(1), pp.195-204 Jan, 2018
- Subject
- 재료공학
- Language
- English
- ISSN
- 2005-4149
1598-9623
The effect of grain size inhomogeneity of large ingot on the hot deformation behavior of Al-8Zn-2Mg-2Cu alloywere investigated using hot compression tests over a temperature range from 300 °C to 450 °C with strain rate from0.1 s-1to 10 s-1. It was found that the grain size (100 μm) in surface layer of the ingot is finer than that of the centrallayer (>200 μm). The surface specimen exhibited lower flow stress than that of central one in the temperature rangefrom 350 °C to 450 °C and the strain rate range from 0.1 s-1to 1 s-1. The softening mechanism is dynamic recovery,together with a partial dynamic recrystallization (DRX) at high temperature and low strain rate condition regardlessthe grain size. The nucleation mechanism of DRX is the strain induced grain boundary migration. Therefore,the DRX fraction is higher in surface specimen because the higher grain boundary density provides more nucleationsites. Based on processing maps, the applicable hot deformation parameters for the large size ingot are determinedto be at the temperature range of 440-450 °C and the strain rate of 0.1-0.3 s-1when taking the grain sizeinhomogeneity into account.