The study investigates the effects of pre-strain on the bake hardenability and precipitation behavior of Al-Mg-Si automotive body sheets. The scanning electron microscopy, transmission electron microscopy, tensile tes...The study investigates the effects of pre-strain on the bake hardenability and precipitation behavior of Al-Mg-Si automotive body sheets. The scanning electron microscopy, transmission electron microscopy, tensile test, Vickers hardness test, and differential scanning calorimetry were conducted for the purpose. It was found that the pre-strain treatment partially inhibits the natural aging hardening effect but cannot completely eliminate it. The pre-straining significantly enhances the bake hardening effect, with the 5% pre-strain sample showing the highest increase in yield strength and hardness. The formation of fine β" precipitates and dislocation structures contribute to the observed strengthening. Additionally, the study highlights the importance of optimizing pre-strain levels to achieve the best balance between strength and ductility in bake-hardened aluminum alloys.展开更多
The effects of Sb and Sr on the modification and refinement of Mg_(17)Al_(12)and Mg_2Si phases in Mg-12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al-0.7Si alloy...The effects of Sb and Sr on the modification and refinement of Mg_(17)Al_(12)and Mg_2Si phases in Mg-12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al-0.7Si 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 Mg_(17)Al_(12)phase was refined and broken into some discontinuous island structures. However, some network Mg_(17)Al_(12)phases still can be detected in Mg-12Al-0.7Si-0.09 Sr alloy. Therefore, Sb performs better in modification and refinement of Mg_(17)Al_(12)phase than does Sr. Small amounts of fine polygonal shaped Mg_2Si phases were found in Mg-12Al-0.7Si-0.5Sb alloy, while the morphology of Mg_2Si phases in Mg-12Al-0.7Si-0.09 Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg_2Si phase are more significant by adding 0.09 wt.% 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 oC.展开更多
The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5...The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.展开更多
文摘The study investigates the effects of pre-strain on the bake hardenability and precipitation behavior of Al-Mg-Si automotive body sheets. The scanning electron microscopy, transmission electron microscopy, tensile test, Vickers hardness test, and differential scanning calorimetry were conducted for the purpose. It was found that the pre-strain treatment partially inhibits the natural aging hardening effect but cannot completely eliminate it. The pre-straining significantly enhances the bake hardening effect, with the 5% pre-strain sample showing the highest increase in yield strength and hardness. The formation of fine β" precipitates and dislocation structures contribute to the observed strengthening. Additionally, the study highlights the importance of optimizing pre-strain levels to achieve the best balance between strength and ductility in bake-hardened aluminum alloys.
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 Mg_(17)Al_(12)and Mg_2Si phases in Mg-12Al-0.7Si alloy were investigated and compared. The microstructure and mechanical properties of Mg-12Al-0.7Si 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 Mg_(17)Al_(12)phase was refined and broken into some discontinuous island structures. However, some network Mg_(17)Al_(12)phases still can be detected in Mg-12Al-0.7Si-0.09 Sr alloy. Therefore, Sb performs better in modification and refinement of Mg_(17)Al_(12)phase than does Sr. Small amounts of fine polygonal shaped Mg_2Si phases were found in Mg-12Al-0.7Si-0.5Sb alloy, while the morphology of Mg_2Si phases in Mg-12Al-0.7Si-0.09 Sr alloy changed from the coarse Chinese script shapes to fine granule and irregular polygonal shapes, indicating that the effects of modification and refinement on Mg_2Si phase are more significant by adding 0.09 wt.% 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 oC.
基金the financial support by the Natioal Natural Science Foundation of China(Nos.:51571086 and 51271073)the financial support from the Natural Science Foundation of Henan Polytechnic University(No.:B2010-20)。
文摘The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.
