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 effect of pre-aging treatment on the tensile properties,formability and microstructures of 2036 aluminum alloy for automobile body sheets were investigated through the tensile tests,DSC analysis and TEM observatio...The effect of pre-aging treatment on the tensile properties,formability and microstructures of 2036 aluminum alloy for automobile body sheets were investigated through the tensile tests,DSC analysis and TEM observation. The results show that the alloy was softened,which was pre-aged at 180 ℃ within 20 min and then natural aging,namely T4P. However,the yield strength decreases first and then rises. The yield strength of the alloy after T4P(10 min) reach the minimal 202.3 MPa,but the elongation and strain hardening exponent arrive at the maximum,25.5% and 0.26 respectively,which can improve its formability effectively. In the early stage of T4P,GP zones dissolve,and generate some θ″ nuclei,so that the strengthening effect is restrained during the natural aging following the pre-aging. With the increment of pre-aging time,the θ″ phases are formed. The number of the θ″ phases grows,and the strength increases sharply during the paint-bake treatment. In contrast with the 6000 series aluminum alloy for automobile body sheets,the paint-bake hardenability of the 2036 alloy is lower and its yield strength before the paint bake is accordingly higher,which will add the difficulty of forming for the sheet.展开更多
A Ti＋Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied. Subsequent cold rolling and continuou...A Ti＋Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied. Subsequent cold rolling and continuous annealing processes were also conducted. The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregular polygonal ferrites. The yield strength, ultimate tensile strength, n value, and r value of the No.2 specimen hot-rolled in the ferrite region with lubrication are 243 MPa, 364 MPa, 0.29, and 1.74, respectively, which are similar to those of the No.1 specimen hot-roiled in the conventional austenite region. The elongation rate and bake hardening value of No.2 specimen are 51% and 49.4 MPa, respectively, which are greater than those of No. 1 specimen. The No.2 specimen hot-rolled in the ferrite region with lubrication exhibits good mechanical properties and relatively excellent baking hardening performance. Therefore, the hot rolling experiment of Ti＋Nb bearing ultra-low carbon bake hardening steel in the ferrite region with lubrication is feasible and can be considered in the future industrial trial production.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Projects (2005-12) supported by the State Key Laboratory of Advanced Design and Manufacture for Vehicle Body Open Foundation of China
文摘The effect of pre-aging treatment on the tensile properties,formability and microstructures of 2036 aluminum alloy for automobile body sheets were investigated through the tensile tests,DSC analysis and TEM observation. The results show that the alloy was softened,which was pre-aged at 180 ℃ within 20 min and then natural aging,namely T4P. However,the yield strength decreases first and then rises. The yield strength of the alloy after T4P(10 min) reach the minimal 202.3 MPa,but the elongation and strain hardening exponent arrive at the maximum,25.5% and 0.26 respectively,which can improve its formability effectively. In the early stage of T4P,GP zones dissolve,and generate some θ″ nuclei,so that the strengthening effect is restrained during the natural aging following the pre-aging. With the increment of pre-aging time,the θ″ phases are formed. The number of the θ″ phases grows,and the strength increases sharply during the paint-bake treatment. In contrast with the 6000 series aluminum alloy for automobile body sheets,the paint-bake hardenability of the 2036 alloy is lower and its yield strength before the paint bake is accordingly higher,which will add the difficulty of forming for the sheet.
基金supported by the"11th five" National Science and Technology Support Project of China (No.2006BAE03A13)
文摘A Ti＋Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied. Subsequent cold rolling and continuous annealing processes were also conducted. The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregular polygonal ferrites. The yield strength, ultimate tensile strength, n value, and r value of the No.2 specimen hot-rolled in the ferrite region with lubrication are 243 MPa, 364 MPa, 0.29, and 1.74, respectively, which are similar to those of the No.1 specimen hot-roiled in the conventional austenite region. The elongation rate and bake hardening value of No.2 specimen are 51% and 49.4 MPa, respectively, which are greater than those of No. 1 specimen. The No.2 specimen hot-rolled in the ferrite region with lubrication exhibits good mechanical properties and relatively excellent baking hardening performance. Therefore, the hot rolling experiment of Ti＋Nb bearing ultra-low carbon bake hardening steel in the ferrite region with lubrication is feasible and can be considered in the future industrial trial production.
