The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured ...The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.展开更多
Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstruc...Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstructures and coarse secondary phases in conventional casting methods hinder the effectiveness of these treatments,leading to reduced ductility,inconsistent properties,and prolonged durations.To overcome these challenges,this study introduces the Strain Integrated Gas-Infusion(SIGI)casting process that integrates strain and gas infusion in the semi-solid state.The impact of the SIGI process on the solution treatment and aging kinetics of AZ91 Mg alloy is explored.The SIGI process refinesα-Mg andβ-Mg_(17)Al_(12)phases,significantly enhancing mechanical properties.Experimental and quantitative analyses reveal that the SIGI process accelerates solute atom dissolution,reducing solution treatment times by half,and promotes faster nucleation and growth of precipitates during aging,shortening aging times by one-third.These improvements result in substantial gains in ultimate tensile strength(~40-50%)and ductility(~20-30%)after age hardening compared to conventional casting.The mechanisms driving these changes,including enhanced nucleation rates,reduced diffusion distances,and microstructural refinement,are discussed.These findings demonstrate the potential of the SIGI casting process to advance magnesium alloy performance for engineering applications.展开更多
基金supported by the National Natural Science Foundation of China(52205382,52225503)National Key Research and Development Program(2023YFB4603300)+1 种基金Key Research and Development Program of Jiangsu Province(BZ2024019,BE2022069)International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(NG2024014,XCA2300501)。
文摘The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.
文摘Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstructures and coarse secondary phases in conventional casting methods hinder the effectiveness of these treatments,leading to reduced ductility,inconsistent properties,and prolonged durations.To overcome these challenges,this study introduces the Strain Integrated Gas-Infusion(SIGI)casting process that integrates strain and gas infusion in the semi-solid state.The impact of the SIGI process on the solution treatment and aging kinetics of AZ91 Mg alloy is explored.The SIGI process refinesα-Mg andβ-Mg_(17)Al_(12)phases,significantly enhancing mechanical properties.Experimental and quantitative analyses reveal that the SIGI process accelerates solute atom dissolution,reducing solution treatment times by half,and promotes faster nucleation and growth of precipitates during aging,shortening aging times by one-third.These improvements result in substantial gains in ultimate tensile strength(~40-50%)and ductility(~20-30%)after age hardening compared to conventional casting.The mechanisms driving these changes,including enhanced nucleation rates,reduced diffusion distances,and microstructural refinement,are discussed.These findings demonstrate the potential of the SIGI casting process to advance magnesium alloy performance for engineering applications.
