激光增材制造高强AlSi7Mg铝合金构件工艺与组织调控研究
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摘要
基于选区激光熔化(SLM)工艺对AlSi7Mg铝合金构件进行激光增材制造实验,研究了激光能量密度对SLM成形AlSi7Mg构件致密化行为、显微组织,Si析出形态及力学性能的影响规律,明晰了AlSi7Mg合金SLM成形熔池内温度场和速度场等物理冶金机制,为激光增材制造AlSi7Mg构件显微组织调控和力学性能提升提供了理论基础。研究表明,随着激光能量密度由150J/m增至175J/m,激光成形构件的致密度由94.6%提升至近乎全密度(99.6%);但过高的激光能量输入(225J/m)则会导致致密度降低至99.0%。过高激光能量密度下,温度过高的熔池使得部分低熔点合金元素蒸发形成气孔是致密化程度下降的主因。激光增材制造AlSi7Mg构件中Si颗粒呈现良好的弥散分布状态,且形态十分细小,呈规则网状分布,但能量密度过高时Si颗粒会发生粗化,不利于合金强韧化。在优化的激光能量密度下(200J/m),激光增材制造AlSi7Mg构件力学性能获得显著提升,显微硬度达165HV,拉伸强度达475.8 MPa,延伸率达6.4%,比传统铸造或粉末冶金AlSi7Mg合金力学性能提高20%以上。
Based on selective laser melting(SLM)process,the AlSi7 Mg aluminum alloy parts were produced for laser additive manufacturing experimental study.The influence of laser energy density on the densification behavior,microstructure,Si precipitation morphology and mechanical properties of of SLM-processed AlSi7 Mg parts were studied.The physical metallurgical mechanism such as temperature field and velocity field in the molten pool of AlSi7 Mg alloy SLM was clarified,which provided a theoretical basis for the microstructure adjustment and mechanical properties of AlSi7 Mg parts in laser additive manufacturing.The results showed that as the laser energy density increased from 150 J/m to 175 J/m,the compaction of laser formed parts increased from 94.6%to almost full density 99.6%.However,overlarge laser energy input(225 J/m)led to a decrease of density to 99.0%.Under high laser energy density,the excessively high temperature of the molten pool caused evaporation of part of low melting elements to form gas pores,which was the main reason for the decrease of densification.The Si particles in the laser additive manufacturing AlSi7 Mg parts exhibited a good dispersion distribution,and the Si particles were very small and presented a regular net-shape.However,excessive laser energy density led to the coarsening of the Si particles,which was deteriorated the mechanical properties of alloy.Under optimized laser energy density(200 J/m),the mechanical properties of the laser additive manufactured AlSi7 Mg parts were improved significantly,with a microhardness of 165 HV,an tensile strength of 475.8 MPa,and an elongation rate of 6.4%.Compared to AlSi7 Mg alloys fabricated by traditional casting or powder metallurgy,the mechanical properties increased by more than 20%.
Based on selective laser melting(SLM)process,the AlSi7 Mg aluminum alloy parts were produced for laser additive manufacturing experimental study.The influence of laser energy density on the densification behavior,microstructure,Si precipitation morphology and mechanical properties of of SLM-processed AlSi7 Mg parts were studied.The physical metallurgical mechanism such as temperature field and velocity field in the molten pool of AlSi7 Mg alloy SLM was clarified,which provided a theoretical basis for the microstructure adjustment and mechanical properties of AlSi7 Mg parts in laser additive manufacturing.The results showed that as the laser energy density increased from 150 J/m to 175 J/m,the compaction of laser formed parts increased from 94.6%to almost full density 99.6%.However,overlarge laser energy input(225 J/m)led to a decrease of density to 99.0%.Under high laser energy density,the excessively high temperature of the molten pool caused evaporation of part of low melting elements to form gas pores,which was the main reason for the decrease of densification.The Si particles in the laser additive manufacturing AlSi7 Mg parts exhibited a good dispersion distribution,and the Si particles were very small and presented a regular net-shape.However,excessive laser energy density led to the coarsening of the Si particles,which was deteriorated the mechanical properties of alloy.Under optimized laser energy density(200 J/m),the mechanical properties of the laser additive manufactured AlSi7 Mg parts were improved significantly,with a microhardness of 165 HV,an tensile strength of 475.8 MPa,and an elongation rate of 6.4%.Compared to AlSi7 Mg alloys fabricated by traditional casting or powder metallurgy,the mechanical properties increased by more than 20%.
引文
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[3]LI JING,LIU MING,MA WENYOU,et al.Effects of process parameters and post-heat treatment on the properties of selective laser melted Ti6Al4V[J].Applied Laser,2017,37(6):779-786.李敬,刘敏,马文有,等.工艺参数及热处理对选区激光熔化Ti6Al4V性能的影响研究[J].应用激光,2017,37(6):779-786.
[4]GUNENTHIRAM V,PEYRE P,SCHNEIDER M,et al.Analysis of laser-melt pool-powder bed interaction during the selective laser melting of a stainless steel[J].Journal of Laser Applications,2017,29(2):022303.
[5]CHEN H,GU D,DAI D,et al.Microstructure and composition homogeneity,tensile property,and underlying thermal physical mechanism of selective laser melting tool steel parts[J].Materials Science&Engineering A,2017(682):297-289.
[6]ZHAO SHUMING,SHEN XIANFENG,YANG JIALIN,et al.Investigation of densification,microstructural and mechanical properties of water-atomized 316Lstainless steel parts fabricated by selective laser melting[J].Applied Laser,2017,37(3):319-326.赵曙明,沈显峰,杨家林,等.水雾化316L不锈钢选区激光熔化致密度与组织性能研究[J].应用激光,2017,37(3):319-326.
[7]DONG PENG,LI ZHONGHUA,YAN ZHENGYU,et al.Research status of selective laser melting of aluminum alloys[J].Applied Laser,2015,35(5):607-611.董鹏,李忠华,严振宇,等.铝合金激光选区熔化成形技术研究现状[J].应用激光,2015,35(5):607-611.
[8]SURYAWANSHI J,PRASHANTH K G,SCUDINO S,et al.Simultaneous enhancements of strength and toughness in an Al-12Si alloy synthesized using selective laser melting[J].Acta Materialia,2016(115):285-294.
[9]GU D D,MEINERS W,WISSENBACH K,et al.Laser additive manufacturing of metallic components:materials,processes and mechanisms[J].International Materials Reviews,2012,57(3):133-164.
[10]PRASHANTH K G,SCUDINO S,ECKERT J.Defining the tensile properties of Al-12Si parts produced by selective laser melting[J].Acta Materialia,2017(126):25-35.
[11]GU D D,SHEN Y.Effects of processing parameters on consolidation and microstructure of W-Cu components by DMLS[J].Journal of Alloys&Compounds,2009,473(1-2):107-115.
[12]ZHANG B,LI Y,BAI Q.Defect formation mechanisms in selective laser melting:a review[J].Chinese Journal of Mechanical Engineering,2017,30(3):515-527.
[13]GONG H,RAFI K,GU H,et al.Analysis of defect generation in Ti-6Al-4Vparts made using powder bed fusion additive manufacturing processes[J].Additive Manufacturing,2014(s1-4):87-98.
[14]YUAN P,GU D,DAI D.Particulate migration behavior and its mechanism during selective laser melting of TiC reinforced Al matrix nanocomposites[J].Materials&Design,2015(82):46-55.
[15]OLOKANMI E O,COCHRANE R F,DALGARNO K W.A review on selective laser sintering/melting(SLS/SLM)of aluminium alloy powders:processing,microstructure,and properties[J].Progress in Materials Science,2015(74):401-477.
[16]DOU L,YUAN Z F,LI J Q,et al.Surface tension of molten Al-Si alloy at temperatures ranging from 923to1 123 K[J].Chinese Science Bulletin,2008,53(17):2593-2598.
[17]ANESTIEV L A,FROYEN L.Model of the primary rearrangement processes at liquid phase sintering and selective laser sintering due to biparticle interactions[J].Journal of Applied Physics,1999,86(7):4008-4017.
[18]BUCHBINDER D,SCHLEIFENBAUM H,HEIDRICH S,et al.High power selective laser melting(HP SLM)of aluminum parts[J].Physics Procedia,2011,12(1):271-278.