期刊
MATERIALS
卷 11, 期 7, 页码 -出版社
MDPI
DOI: 10.3390/ma11071233
关键词
quasi-static tensile deformation; Al-Zn-Mg-Cu alloy; plastic deformation; fracture morphology; microstructure
类别
资金
- National Natural Science Funds for Excellent Young Scholars [51422503]
- Special Projects for Development of National Major Scientific Instruments and Equipment [2012YQ030075]
- Major project of Jilin Province Science and Technology Development Plan [2015203014GX]
- Fund Guiding on Strategic Adjustment of Jilin Provincial Economic Structure Project [2014Z045]
- Special Fund Project of Jilin Provincial Industrial Innovation [2016C030]
- Jilin Provincial Middle and Young Scientific and Technological Innovation Talent and Team Project [20170519001JH]
- Program for JLU Science and Technology Innovative Research Team [2017TD-04]
Effects of temperature and strain rate on the fracture behaviors of an Al-Zn-Mg-Cu alloy are investigated by isothermal uniaxial tensile experiments at a wide range of temperatures and strain rates, from room temperature (RT) to 400 degrees C and from 10(-4) s(-1) to 10(-1) s(-1), respectively. Generally, the elevation of temperature leads to the increasing of elongation to fracture and the reduction of peak stress, while higher strain rate results in the decreasing of elongation to fracture and the increasing of peak stress. Interestingly, we found that the coefficient of strain rate sensitivity (m-value) considerably rises at 200 degrees C and work of fracture (W-f) fluctuates drastically with the increase of strain rate at RT and 100 degrees C, both of which signify a non-uniform and unstable deformation state below 200 degrees C. A competition of work hardening (WH) and dynamic recrystallization (DRX) exists at 200 degrees C, making it serve as a transitional temperature. Below 200 degrees C, WH is the main deformation mechanism of flow stress, and DRX dominates the flow stress above 200 degrees C. It has been found that from RT to 200 degrees C, the main feature of microstructure is the generation of dimples and microvoids. Above 200 degrees C, the coalescence of dimples and microvoids mainly leads to the failure of specimen, while the phenomenon of typically equiaxed dimples and nucleation appear at 400 degrees C. The observations of microstructure are perfectly consistent with the related macroscopic results. The present work is able to provide a comprehensive understanding of flow stress of an Al-Zn-Mg-Cu alloy at a wide range of temperatures and strain rates, which will offer valuable information to the optimization of the hot forming process and structural design of the studied alloy.
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