Effect of aging time on discontinuous precipitates, continuous precipitates and mechanical properties of AZ80A magnesium alloy
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;
4. Department of Prosthodontics, Center of Stomatology, Xiangya Hospital, Central South University, Changsha 410008, China)
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;
4. Department of Prosthodontics, Center of Stomatology, Xiangya Hospital, Central South University, Changsha 410008, China)
Abstract: The evolution of precipitates and mechanical properties of AZ80A magnesium alloy with aging time was studied by in situ observation with SEM, TEM and tensile testing. The results show that the continuous precipitation (CP) phases near the reaction front (RF) are replaced by the discontinuous precipitation (DP) phases at the early aging stage. In DP regions, the elliptical phases coarsen obviously with the increase of aging time, which results in a slightly slow reduction of the intracrystalline hardness of DP regions. In CP regions, some small plate phases reprecipitate simultaneously with the growth of the initial precipitates, which contributes to a slight increase in the intracrystalline hardness in CP regions at the later aging stage. The aging hardening of DP regions is faster and stronger than that of CP regions. However, the age strengthening of CP regions not only compensates for the overaging softening of DP regions but also improves the strength of the alloy.
Key words: age hardening; discontinuous precipitation; coarsening; in situ observation; mechanical properties; magnesium alloy