The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grai...The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni,accompanied by the formation of Q(Al3Mg9Si7Cu2)precipitates around the spherical Fe-rich phases.Additionally,Ni addition is beneficial to reducing the grain size in the as-cast state.During the homogenization process,Q phases could be completely dissolved and the grain size could remain basically unchanged.However,compared with the Ni-free alloy,the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment.After thermomechanical processing,the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy.Accordingly,a reasonable Ni addition positively affected the microstructure and formability of the alloys.展开更多
The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with t...The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with the amount of Ca added to the melt.The optimal microstructure and properties were obtained by adding 0.06 wt%Ca to Al-7 Si-0.3 Mg alloy.The secondary dendrite arm spacing(SDAS)of the primaryαphase decreased from 44.41μm to 19.4μm,and the eutectic Si changed from coarse plates to fine coral.The length of the Fe-rich phase(β-Al5 Fe Si)decreased from 30.2μm to 3.8μm,and the Brinell hardness can reach to 66.9.The ultimate tensile strength,yield strength,and elongation of the resulting alloy increased from 159.5 MPa,79 MPa,and 2.5%to 212 MPa,86.5 MPa,and 4.5%,respectively.The addition of Ca can effectively refine the primaryαphase and modify the eutectic Si phase,likely because Ca enrichment at the front of the solid-liquid interface led to undercooling of the alloy,reduced the growth rate of the primaryαphase,and refined the grain size.Also,it could increase the latent heat of crystallization,undercooling,and the nucleation rate of eutectic Si,which was beneficial to the improvement of the morphology of eutectic Si.展开更多
In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in diffe...In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in different states,especially after hot extrution and solid solution treatment,was systematically studied using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and mechanical tests at room temperature.The results show that 0.2wt.% Mn can both refine the as-cast microstructure of the alloy and strengthen the extrusion+T6 state alloy without damaging the plasticity badly due to the formation of Al 15(FeMn) 3 Si 2 and Al 15 Mn 3 Si 2 dispersoids.Compared with the extrusion+T6 state alloy without Mn addition,the ultimate tensile strength and yield strength of the alloy with 0.2wt.% Mn addition are increased from 416.9 MPa to 431.4 MPa,360.8 MPa to 372 MPa,respectively.The elongation of the extrusion+T6 state alloy does not show obvious change when the Mn addition is less than 0.5wt.%,and for the alloy with 0.2wt.% Mn addition its elongation is still as high as 15.6%.However,when over 0.7wt.% Mn is added to the alloy,some coarse,stable and refractory AlVMn and Al(VMn)Si phases form.These coarse phases can reduce the effect of Mn on the inhibition of re-crystallization;and they retain the angular morphology permanently after the subsequent deformation process and heat treatment.This damages the mechanical properties of the alloy.展开更多
An ultrasonic vibration-assisted air-cooled stirring rod process(ACSR+UV)was used to efficiently prepare a large-volume semisolid slurry with a mass of more than 40 kg.A low-cost Al–Si–Fe–Mg–Cu–Zn die-casted allo...An ultrasonic vibration-assisted air-cooled stirring rod process(ACSR+UV)was used to efficiently prepare a large-volume semisolid slurry with a mass of more than 40 kg.A low-cost Al–Si–Fe–Mg–Cu–Zn die-casted alloy with high thermal conductivity,high plasticity and medium strength was developed.The alloy was used to manufacture large,thin-walled parts for 5 G base stations by using the ACSR+UV rheological die-casting(ACSR+UV R-DC)process.Investigations were performed on the microstructure,porosity,mechanical properties,fracture behaviour and thermal conductivity of the ACSR+UV R-DC alloy,which was then compared to traditionally die-casted(T-DC)and ACSR R-DC alloys.The mechanisms for the microstructural refinement and enhancement of the mechanical and thermal conductivity performances of the ACSR+UV R-DC alloy were also analysed.The results showed that the ACSR+UV process increased the nucleation rate of the melt due to the increase in the nucleation area and the generation of cavitation bubbles.A radial-and an axial-forced convection was also generated inside the melt under the combined effects of acoustic flow and mechanical stirring,thereby homogenising the melt composition field and the temperature field.Therefore,the ACSR+UV R-DC process not only refined the primaryα-Al(α_(1)-Al),the eutectic silicon and the secondaryα-Al(α_(2)-Al),but also greatly improved the morphology and the distribution of the β-Al5FeSi phase.The mechanical properties of the ACSR+UV R-DC alloy were higher than those of the T-DC and the ACSR R-DC alloys.Compared to the T-DC alloy,the ultimate tensile strength,elongation and yield strength of the ACSR+UV R-DC alloy were increased by 34%,122%and 19%,respectively.This was because the ACSR+UV R-DC technique gave the alloy the characteristics of high density,fine sphericalα1-Al grain and a fine and uniform β-phase,which improved the fracture behaviour of the alloy.The thermal conductivity of the ACSR+UV R-DC alloy was 184 W/(m K),which was 10.2%and 3.4%higher than that of T-DC and ACSR R-DC alloys,respectively.This was because the refined eutectic silicon and β phases in the ACSR+UV R-DC alloy facilitated an easier electron flow through the eutectic region,and the decrease in porosity increased the effective area of heat conduction.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0300801)the National Natural Science Foundation of China(Nos.51871029,51571023,and 51301016)+2 种基金Beijing Natural Science Foundation(No.2172038)Beijing Laboratory of Metallic Materials and Processing for Modern Transportation(No.FRF-SD-B-005B)The China Scholarship Council for financial support to M.X.Guo
文摘The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni,accompanied by the formation of Q(Al3Mg9Si7Cu2)precipitates around the spherical Fe-rich phases.Additionally,Ni addition is beneficial to reducing the grain size in the as-cast state.During the homogenization process,Q phases could be completely dissolved and the grain size could remain basically unchanged.However,compared with the Ni-free alloy,the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment.After thermomechanical processing,the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy.Accordingly,a reasonable Ni addition positively affected the microstructure and formability of the alloys.
基金financially supported by the National High-tech R&D Program of China (No. 2014AA041804)International S&T Cooperation Program of China (No. 2014DFA53050)
文摘The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with the amount of Ca added to the melt.The optimal microstructure and properties were obtained by adding 0.06 wt%Ca to Al-7 Si-0.3 Mg alloy.The secondary dendrite arm spacing(SDAS)of the primaryαphase decreased from 44.41μm to 19.4μm,and the eutectic Si changed from coarse plates to fine coral.The length of the Fe-rich phase(β-Al5 Fe Si)decreased from 30.2μm to 3.8μm,and the Brinell hardness can reach to 66.9.The ultimate tensile strength,yield strength,and elongation of the resulting alloy increased from 159.5 MPa,79 MPa,and 2.5%to 212 MPa,86.5 MPa,and 4.5%,respectively.The addition of Ca can effectively refine the primaryαphase and modify the eutectic Si phase,likely because Ca enrichment at the front of the solid-liquid interface led to undercooling of the alloy,reduced the growth rate of the primaryαphase,and refined the grain size.Also,it could increase the latent heat of crystallization,undercooling,and the nucleation rate of eutectic Si,which was beneficial to the improvement of the morphology of eutectic Si.
基金financially supported by the Fundamental Research Funds for Central Universities of China(Grant Nos.N110609002and N110408005)
文摘In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in different states,especially after hot extrution and solid solution treatment,was systematically studied using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and mechanical tests at room temperature.The results show that 0.2wt.% Mn can both refine the as-cast microstructure of the alloy and strengthen the extrusion+T6 state alloy without damaging the plasticity badly due to the formation of Al 15(FeMn) 3 Si 2 and Al 15 Mn 3 Si 2 dispersoids.Compared with the extrusion+T6 state alloy without Mn addition,the ultimate tensile strength and yield strength of the alloy with 0.2wt.% Mn addition are increased from 416.9 MPa to 431.4 MPa,360.8 MPa to 372 MPa,respectively.The elongation of the extrusion+T6 state alloy does not show obvious change when the Mn addition is less than 0.5wt.%,and for the alloy with 0.2wt.% Mn addition its elongation is still as high as 15.6%.However,when over 0.7wt.% Mn is added to the alloy,some coarse,stable and refractory AlVMn and Al(VMn)Si phases form.These coarse phases can reduce the effect of Mn on the inhibition of re-crystallization;and they retain the angular morphology permanently after the subsequent deformation process and heat treatment.This damages the mechanical properties of the alloy.
基金the National Natural Science Foundation of China(Nos.52005034 and 52027805)the Fundamental Research Funds for the Central Universities(No.FRF-TP-18-043A1)+1 种基金the Zhuhai Industry-University-Research Cooperation Project(No.ZH22017001200176PWC)the China Postdoctoral Science Foundation Funded Project(No.2019M650486)。
文摘An ultrasonic vibration-assisted air-cooled stirring rod process(ACSR+UV)was used to efficiently prepare a large-volume semisolid slurry with a mass of more than 40 kg.A low-cost Al–Si–Fe–Mg–Cu–Zn die-casted alloy with high thermal conductivity,high plasticity and medium strength was developed.The alloy was used to manufacture large,thin-walled parts for 5 G base stations by using the ACSR+UV rheological die-casting(ACSR+UV R-DC)process.Investigations were performed on the microstructure,porosity,mechanical properties,fracture behaviour and thermal conductivity of the ACSR+UV R-DC alloy,which was then compared to traditionally die-casted(T-DC)and ACSR R-DC alloys.The mechanisms for the microstructural refinement and enhancement of the mechanical and thermal conductivity performances of the ACSR+UV R-DC alloy were also analysed.The results showed that the ACSR+UV process increased the nucleation rate of the melt due to the increase in the nucleation area and the generation of cavitation bubbles.A radial-and an axial-forced convection was also generated inside the melt under the combined effects of acoustic flow and mechanical stirring,thereby homogenising the melt composition field and the temperature field.Therefore,the ACSR+UV R-DC process not only refined the primaryα-Al(α_(1)-Al),the eutectic silicon and the secondaryα-Al(α_(2)-Al),but also greatly improved the morphology and the distribution of the β-Al5FeSi phase.The mechanical properties of the ACSR+UV R-DC alloy were higher than those of the T-DC and the ACSR R-DC alloys.Compared to the T-DC alloy,the ultimate tensile strength,elongation and yield strength of the ACSR+UV R-DC alloy were increased by 34%,122%and 19%,respectively.This was because the ACSR+UV R-DC technique gave the alloy the characteristics of high density,fine sphericalα1-Al grain and a fine and uniform β-phase,which improved the fracture behaviour of the alloy.The thermal conductivity of the ACSR+UV R-DC alloy was 184 W/(m K),which was 10.2%and 3.4%higher than that of T-DC and ACSR R-DC alloys,respectively.This was because the refined eutectic silicon and β phases in the ACSR+UV R-DC alloy facilitated an easier electron flow through the eutectic region,and the decrease in porosity increased the effective area of heat conduction.
