The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and i...The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and its modification mechanism by Sb and Sr were investigated using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and differential thermal analysis （DTA）. The results indicate that by adding 0.5wt.% Sb to the Mg-12Al-0.7Si alloy, the Mg17Al12 phase was refined and broken into some discontinuous island structures. However, some network Mg17Al12 phases still can be detected in Mg-12Al-0.7Si-0.09Sr alloy. Therefore, Sb performs better in modification and refinement of Mg17Al12 phase than does Sr. Small amounts of fine polygonal shaped Mg2Si phases were found in Mg-12AI-0.7Si-0.5Sb alloy, while the morphology of Mg2Si phases in Mg-12Al-0.7Si-0.09Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg2Si phase are more significant by adding 0.09wt.% Sr than 0.5wt.% Sb. The ultimate tensile strengths of the Sb and Sr modified Mg-12Al-0.7Si alloys were considerably increased both at room temperature and at 200 ℃.展开更多
Microstructural evolution of AZ91 magnesium alloy was investigated during homogenizing annealing treatment, hot extrusion and ageing treatment, respectively. The results exhibited that both the divorced eutectic β-Mg...Microstructural evolution of AZ91 magnesium alloy was investigated during homogenizing annealing treatment, hot extrusion and ageing treatment, respectively. The results exhibited that both the divorced eutectic β-Mg17Al12 and the precipitated β-Mg17Al12 phases appeared in the as-cast alloy. The β-Mg17Al12 phase dissolved into α-Mg matrix mostly and the structure kept fine after the optimized homogenization treatment at 380 °C for 15 h. Dynamic recrystallization and consequent grain refinement occurred during extrusion. The banded β-Mg17Al12 precipitates paralleled to the extrusion direction were observed after ageing treatment. The banded precipitation should be attributed to the solidification segregation which was elongated during the subsequent extrusion. Furthermore, the effects of temperature, holding time of homogenization and ageing treatment, and extrusion processing parameters on the microstructural evolution of AZ91 alloy were also discussed in details according to the experimental results.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant nos.:51301118,51404166)the Projects of International Cooperation in Shanxi province,China(Grant no.:2014081002)and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi province,China(Grant nos.:2013108,2014120)
文摘The effects of Sb and Sr on the modification and refinement of Mg17Al12 and Mg2Si phases in Mg- 12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al0.7Si alloy and its modification mechanism by Sb and Sr were investigated using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and differential thermal analysis （DTA）. The results indicate that by adding 0.5wt.% Sb to the Mg-12Al-0.7Si alloy, the Mg17Al12 phase was refined and broken into some discontinuous island structures. However, some network Mg17Al12 phases still can be detected in Mg-12Al-0.7Si-0.09Sr alloy. Therefore, Sb performs better in modification and refinement of Mg17Al12 phase than does Sr. Small amounts of fine polygonal shaped Mg2Si phases were found in Mg-12AI-0.7Si-0.5Sb alloy, while the morphology of Mg2Si phases in Mg-12Al-0.7Si-0.09Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg2Si phase are more significant by adding 0.09wt.% Sr than 0.5wt.% Sb. The ultimate tensile strengths of the Sb and Sr modified Mg-12Al-0.7Si alloys were considerably increased both at room temperature and at 200 ℃.
基金Project (2011A090200104) supported by Guangdong Science and Technology Special Projects, China
文摘Microstructural evolution of AZ91 magnesium alloy was investigated during homogenizing annealing treatment, hot extrusion and ageing treatment, respectively. The results exhibited that both the divorced eutectic β-Mg17Al12 and the precipitated β-Mg17Al12 phases appeared in the as-cast alloy. The β-Mg17Al12 phase dissolved into α-Mg matrix mostly and the structure kept fine after the optimized homogenization treatment at 380 °C for 15 h. Dynamic recrystallization and consequent grain refinement occurred during extrusion. The banded β-Mg17Al12 precipitates paralleled to the extrusion direction were observed after ageing treatment. The banded precipitation should be attributed to the solidification segregation which was elongated during the subsequent extrusion. Furthermore, the effects of temperature, holding time of homogenization and ageing treatment, and extrusion processing parameters on the microstructural evolution of AZ91 alloy were also discussed in details according to the experimental results.
