Microstructure And Properties Of AlCuTi Alloys Prepared By Additive Manufacturing

With the development of science and technology,additive manufacturing technology has gradually entered the field of vision of researchers,which has injected new vitality into a series of industries such as aerospace and automobile industry.The ability to use selective laser melting(SLM)to fabricate complex structures is another breakthrough in current aerospace aluminum alloys.However,the problem of hot cracking in aluminum-copper alloys which usually used in aerospace,has limited their further application in additive manufacturing technology.This makes the development of new aluminum-copper alloy systems suitable for SLM technology particularly important.As the element with the highest growth limiting factor in aluminum alloys,titanium can effectively promote the composition supercooling of aluminum-copper alloys,thereby forming fine grains and hindering the formation of hot cracks.In this experiment,AlCuTi ternary alloys were prepared using SLM technology.The effects of SLM process parameters on the microstructure,mechanical properties and tribological properties of AlCuTi alloys were studied.The corresponding relationship between forming process,microstructure,mechanical properties and tribological properties was explained in detail.The strengthening mechanism of Ti element on Al Cu alloy was studied,and the following main conclusions were drawn:(1)After adding an appropriate amount(1.5 wt.%)of Ti element,the cracking problem of the Al Cu binary alloy is effectively solved,and the grain size is significantly refined;the AlCuTi alloy formed by SLM has a bimodal structure formed by alternating coarse grains and fine grains;(2)The laser volume energy density(VED)of SLM has a significant effect on the density of the formed AlCuTi alloy.The alloy density increases first and then decrease with the increase of VED,and reaches a higher value when the VED is in the range of 70-100 J/mm~3.70-100 J/mm~3is the best process parameters for the preparation of AlCuTi alloy by SLM;(3)The mechanical properties and tribological properties of SLM-formed AlCuTi alloys are also affected by the VED.The strength and hardness of the alloy show a trend of first increase and then decrease with the increase of VED,and are at higher strength and hardness at 70-100J/mm~3,that is,the tensile strength is 300±20 MPa,and the plasticity exceeds 10%,the hardness is 110±10 HV;the wear performance also increases first and then decreases with the increase of VED,which has the same trend with mechanical properties and hardness;(4)The time of low temperature aging treatment has a significant effect on the final properties of AlCuTi alloy.The mechanical properties of the samples after low temperature aging at 190°C for 8 h were the best,the strength was increased from 300 MPa to 350 MPa,and the plasticity was increased from 10%to 12%.The tribological properties decreased first and then increased with the increase of aging treatment time,and the friction and wear properties reach the best when the aging treatment time was 2 h.