Effect of Argon Flow Rate on Elongation Ratio of Ti6Al4V Alloy Synthesized by Selective Laser Melting

Ti6Al4V alloy coatings,an advanced electric motor material,were synthesized by selective laser melting(SLM) of Ti6Al4V powder on Ti-alloy substrate.The influence of the Ar flow-rate on the microstructures and tensile properties was investigated with X-ray diffraction,scanning electron microscopy and tensile measurement.The results show that Ar flow-rate had a major impact.To be specific,white α'-phased tissues formed in laser melted Ti6Al4V alloy,and a flow-rate of 6 L/min promoted in-situ decomposition of martensite.As the Ar flow-rate increased,the elongation ratio changed in an increase-decrease mode,maximizing at 6 L/min,and the yield/tensile strengths varied slightly.Laser melting turned a large amount of α-phased hcp-structured tissue,0.5 μm in width,into some(α+β)-phased clusters.An increasing dimple-density formed around tearing ridges at 6 L/min,indicating the peak of elongation ratio; and no cleavage plane appeared near the fractures.