Facing The Study On Formability Of Ti6Al4V Alloy Formed By Multi-laser Beam Selective Laser Melting

In recent years,selective laser melting(SLM)technology can rapidly manufacture complex,precise metal components,and is widely used in aerospace,automotive,energy and medical fields.At present,the small size and low efficiency of SLM fabricating parts limit the application of SLM technology in engineering fields.Multi-laser beam selective laser melting technology is effective way to solve these problems.In the process of multi-laser SLM,each laser is responsible for different fabricating areas,and different areas overlap each other to form the whole part.Due to the different laser scanning times of overlap area and no-overlap area,the overall performance of the parts is different.In view of the above problems,Ti6Al4 V powder was used as raw material to study the formability of multi-laser beam SLM and the influence mechanism of heat treatment on the formability of multi-laser beam SLM.The specific research contents and main conclusions are as follows:The macro-morphology of Ti6Al4 V alloy fabricated by multi-laser SLM was studied.By studying the influence mechanism of different scanning times of laser on surface quality and pore defects,the surface morphology,roughness and pore defects of overlap and no-overlap region of Ti6Al4 V alloy fabricated by multi-laser SLM were obtained.It is found that there are obvious protrusions and “ridges” of protrusions at the intersection boundary of overlap and no-overlap area.With the increase of scanning times,the upper surface roughness first decreases and then increases,the side surface roughness increases all the time,and the upper surface porosity first decreases and then increases.The mechanical properties and microstructure of Ti6Al4 V alloy fabricated by multi-laser SLM was studied.By studying the influence mechanism of different scanning times of laser on microstructure and mechanical properties,microstructure,phase composition,vickers hardness,wear resistance,tensile properties of overlap and no-overlap region of Ti6Al4 V alloy fabricated by multi-laser SLM were obtained.The results show that: with the increase of scanning times,the size of acicular martensite α′ on the upper surface increases gradually,and the microstructure of side surface is composed of the columnar grains and the width of the columnar grains fabricated by four-scanning forming is the widest;In terms of hardness,with the increase of scanning times,the hardness decreases gradually;In terms of wear resistance,with the increase of scanning times,the friction coefficient decreases gradually,and the surface wear first decreases and then increases;In terms of tensile strength,when the overlap width is 0.1 mm,the tensile strength of overlap area is lower than that of no-overlap area,and the width of overlap area is 0.2mm～1.0mm,the tensile strength of overlap area are higher than those of no-overlap area.The effect of heat treatment on the mechanical properties and microstructure of Ti6Al4 V alloy fabricated by multi-laser SLM was studied.The Ti6Al4 V alloy was annealed at650℃/4h and 750℃/4h to explore the influence mechanism of heat treatment on the formability consistency of multi-laser SLM.It is found that comparing with the samples with different scanning times of before heat treatment,when annealing process is 650℃/4h,acicular martensite α′ transforms into α+β phase and a small amount of α′ remains.When annealing process is 750℃/4h,the degree of transformation from acicular martensite α′ to transform into α+β phase is increased,and the microstructure further coarsens.However,when annealing process is 650℃/4h or 750℃/4h,the microstructure,phase composition,vickers hardness and tensile properties of the samples fabricated by one-scanning forming,two-scanning forming and four-scanning forming have no significant changes.