| Selective laser melting（SLM）is widely used in aluminum alloy rapid prototyping due to its advantages of simple design process,high forming accuracy and excellent mechanical properties.However,the current research on the preparation of aluminum alloys by SLM is mostly limited to Al-Si（-Mg）series cast aluminum alloys,such as Al Si10Mg,Al Si12,etc.For Al-Cu high-strength alloys,due to the high content of alloying elements and wide solidification interval,hot cracking is easy to occur in SLM forming process,which seriously reduces the mechanical properties of the forming parts.By adding alloying elements or grain refiners,the grains can be refined effectively and the hot cracks can be inhibited during SLM molding.Therefore,in this paper,（ZrH2+Ti H2）/Al-Cu-Mn composite powder was prepared by mechanical mixing method,and the sample was formed by selective laser melting technology.The effects of SLM process parameters,addition amount of ZrH2+Ti H2 and subsequent heat treatment on microstructure and mechanical properties of zirconium and titanium Al-Cu-Mn alloy formed by SLM were investigated.The purpose is to provide technical support for SLM forming Al-Cu-Mn high strength aluminum alloy with good mechanical properties.The effects of process parameters on the density,internal defects and mechanical properties of（0.75wt.%ZrH2+0.75wt.%Ti H2）/Al-Cu-Mn composite powder were investigated.With the increase of laser energy density,the internal defects of the sample gradually transform from irregular holes to spherical holes,and the spherical holes become more and more with the further increase of laser energy density,and their density increases first and then decreases.When the laser energy density is 120J/mm3,the sample reaches the highest density of 96.7%.The corresponding process parameters are 260W laser power and 600mm/s scanning speed.At the same time,the microhardness and tensile properties are also obtained by this process.The effects of ZrH2+Ti H2 addition on the internal defects,microstructure and mechanical properties of SLM formed Al-Cu-Mn alloy were investigated.The results show that the addition of ZrH2 and Ti H2 can effectively refine the grain and reduce the thermal crack.With the increase of ZrH2 and Ti H2 addition,the columnar crystal structure gradually changed to equiaemic crystal,and the thermal cracks decreased.When 0.75wt.%ZrH2 and Ti H2 were added respectively,the internal thermal cracks of the samples disappeared completely,and the samples had high density at the same time,so the mechanical properties of the samples reached the best.The microhardness reached 121.5HV,and the tensile strength,yield strength and elongation increased to356.5MPa,287.1MPa and 8.8%,respectively.The heat treatment of（0.75wt.%ZrH2+0.75wt.%Ti H2）/Al-Cu-Mn composite powder SLM was studied.The results showed that:under the premise of maintaining better treatment effect and treatment time,solution at 540℃for 1h and then artificial aging at 180℃for 8h are the most suitable heat treatment process parameters.After heat treatment,a large number of fine Al2Cu dispersion phases were precipitated in the microstructure of the samples.Under the action of the dispersion phase,the microhardness and tensile properties of the samples were improved,and the microhardness reached 142.7HV,which was 17.4%higher than that of the samples without heat treatment.The tensile strength and yield strength of the samples are460.9MPa,327.5MPa and 11.4%respectively.Compared with untreated samples,the samples increased by 29.3%,14.1% and 2.6% respectively. |
PDF Full Text Request