Thermal stability of nanocrystalline in surface layer of
magnesium alloy AZ91D
magnesium alloy AZ91D
(1. Institute of Advanced Material, University of Science and Technology Beijing, Beijing 100083, China;
2. College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400050, China;
3. Nanjing Kerun Lubricants Co., Ltd., Nanjing 211100, China)
2. College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400050, China;
3. Nanjing Kerun Lubricants Co., Ltd., Nanjing 211100, China)
Abstract: Isothermal and isochronal annealing was conducted to study the thermal stability of the nanocrystalline in the surface layer of Mg alloy AZ91D induced by high-energy shot peening (HESP). Field emission scanning electron microscope (FESEM) and X-ray diffractometer were used to characterize the microstructure. Results showed that nanocrystalline produced by HESP on the surface layer of the magnesium alloy AZ91D was 60−70 nm on average. The nanocrystalline could remain stable at about 100 ˚C, and grew up slowly between 100 ˚C and 200 ˚C. When the annealing temperature reached 300 ˚C, the growth rate of the nanocrystalline increased significantly. The kinetic coefficient n of the nanocrystalline growth was calculated to be 2−3 and the grain growth activation energy Q=39.7 kJ/mol, far less than the self-diffusion activation energy of magnesium atoms in the coarse polycrystalline material.
Key words: high energy shot peening (HESP); magnesium alloy; AZ91D; nanocrystalline; thermal stability