Research On Preparation And Selective Laser Melting Of TiB₂/AlSi10Mg Composite Powders

Aluminum alloys have attracted considerable attentions in selective laser melting,because they are typical lightweight materials.However,aluminum alloys are inherently low laser absorptivity,high thermal conductivity and highly susceptible to oxidization,which become the hurdles to their further application in selective laser melting.Compared to other aluminum alloy system?Al-Cu-Mg,Al-Zn-Mg,etc.?,AlSi10Mg is more suitable for SLM,because it possesses better castability and weldability.But it belongs to moderate strength alloy system,which is inadequate to meet the increasing industrial needs.It is a feasible way to improve the properties of aluminum alloy by preparing composites.In terms of selective laser melting,the morphology of composites prepared by the common method mechanical alloyingwould be damaged,which influence the outspreading of composite powders during SLM process.In order to improve the SLM formability of aluminum alloy,a method combined mechanical alloying and plasma spheroidizaiton treatment was used to fabricate high sphericity TiB₂/AlSi10Mg composites in this study,which not only could enhance the flowability of powders,but also control the component of powder surfacre.For better understanding this TiB₂/AlSi10Mg composites,we attempt to carry out the work from powder charactertics and forming effect.On the one hand,the characteristics of TiB₂/AlSi10Mg composites,such as morphology,structure,size distribution,phase composition and laser absorptivity,have been detailed studied.On the other hand,the formability of selective laser melting TiB₂/AlSi10Mg were verified,and the process parameters,microstructure and mechanical properties of printed have been discussed.The main conclusions were presented as follows:1.TiB₂/AlSi10Mg composite powders with high sphericity,good dispersity and size distribution uniform were obtained by combined mechanical alloying and plasma spheroidizaition treatment.Compared to aluminum alloy composite powders prepared by only mechanical alloying,it has a better selective laser melting formability due to these characteristics.2.The laser absorptivity of TiB₂/AlSi10Mg composites has increased from 23.2%?AlSi10Mg?to 42.1%.On the one hand,the AlSi10Mg powder was decorated by TiB₂,and on the other hand,the surface of TiB₂/AlSi10Mg composite powders fabricated by combined mechanical alloying and plasma treatment was rough,which increases the times of laser reflections and laser absorptivity.Therefore,compared to previous reported?60J/mm³?,dense TiB₂/AlSi10Mg printed could be obtained in a lower laser energy density?51.3J/mm³?due to the increase of laser absorptivity.3.The structure of TiB₂/AlSi10Mg composites is TiB₂ adhered on AlSi10Mg surface,which enhance the laser absorptivity of powder and influence the heat transfer beaviour.Thereby,the molten pool change from keyhole mode melting to heat conduction melting domination,which restrain the formation of keyhole pores.4.The aim to improve the strength of SLM AlSi10Mg was realized by preparing TiB₂/AlSi10Mg composites,and the strength of TiB₂/AlSi10Mg composites could reach at413 MPa,and the main strengthening mechanisms are Hall-Petch strengthening,Orowan strengthening and dispersion strengthening.Among these strengthening mechanisms,dispersion strengthening plays an important role in strengthening TiB₂/AlSi10Mg composites.