Study On Microstructure And Properties Of Ni₁₀Cr₆W₁Fe₉Ti₁ High Entropy Alloy By Selective Laser Melting

High-entropy alloy（HEA）has excellent mechanical and physical properties and great potential in industrial production.Since its introduction,it has generally followed the design criteria of equal atomic ratio or near equal atomic ratio.The HEA designed under this criterion has high cost,especially for some multi-principal HEA containing precious metal elements or rare metal elements.The non-equiatomic ratio HEA has gradually attracted widespread attention due to its low economic cost and wide design range.The preparation methods of traditional HEA are mainly vacuum arc melting,vacuum induction melting,etc.The HEA produced by traditional casting method is prone to internal element segregation and uneven structure,and the mechanical properties are low,which requires subsequent processing.In contrast,HEA prepared by SLM（Selective Laser Melting）has significant element uniformity and excellent mechanical properties,making people more and more interested in manufacturing HEA by SLM.Therefore,Ni₁₀Cr₆W₁Fe₉Ti₁ HEA with non-equiatomic ratio was selected as the research object,and the forming process of the alloy was explored.The effects of scanning angles（0°,15°,30°,60°,67°and 90°）on the phase composition,microstructure texture,grain deflection and mechanical properties of SLM-formed Ni₁₀Cr₆W₁Fe₉Ti₁ HEA and the strengthening and toughening mechanism of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA were systematically studied.It lays a theoretical and technical foundation for realizing the directional growth and regulation of grains,achieving consistent,repeatable and accurate microstructure control and excellent performance.The main conclusions are as follows:（1）The relative density of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA prepared by laser melting increases first and then decreases with the increase of bulk energy density.In addition,when the laser power and overlap spacing are fixed and the scanning speed changes,the relative density of Ni₁₀Cr₆W₁Fe₉Ti₁HEA increases first and then decreases with the increase of scanning speed.when the scanning speed and overlap spacing are fixed and the laser power changes,the relative density of Ni₁₀Cr₆W₁Fe₉Ti₁HEA increases first and then decreases with the increase of scanning speed.when the scanning speed and laser power are fixed and the overlap spacing changes,the relative density of Ni₁₀Cr₆W₁Fe₉Ti₁HEA increases first and then decreases with the increase of scanning speed.The final optimized Ni₁₀Cr₆W₁Fe₉Ti₁ HEA forming process is that the scanning speed is 2200 mm/s,the laser power is265 W,the overlap spacing is 0.07 mm and the layer thickness is 0.03 mm.At this time,the alloy sample reaches the highest density of 97.95%.（2）The change of scanning angle（0°,15°,30°,60°,67°and 90°）will not affect the phase composition and element distribution of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA,but will cause periodic arrangement of different layers and different morphologies of molten pool.The preset scanning angle in the process parameters is basically the same as the angle of the columnar grain deflection growth between the layers.With the increase of the scanning angle,the growth condition of the direct epitaxial growth of the columnar crystal is broken,and the vertical epitaxial growth is gradually intensified.In addition,with the increase of the rotation period,the orientation of the strong texture in the alloy gradually concentrates on the{112}and{313}directions,and the grains are gradually refined.When the scanning angle（rotation period）is 67°（180）,the grains in the alloy are the smallest,and the average grain size is 22.77μm.（3）The tensile strength of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA is positively correlated with the rotation period,and increases with the increase of rotation period.When the scanning angle（rotation period）is 67°（180）,the mechanical properties are the best.At small rotation cycles（0°,60°and 90°）,the fracture mechanism of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA is mainly ductile-brittle mixed fracture mechanism dominated by brittle fracture.At large rotation cycles（15°,30°and 67°）,the fracture mechanism is mainly ductile-brittle mixed fracture mechanism dominated by ductile fracture.In addition,under the multiple strengthening mechanisms of solid solution strengthening,fine grain strengthening,second phase strengthening and TWIP（twinning induced plasticity）,the tensile strength of Ni₁₀Cr₆W₁Fe₉Ti₁ HEA reaches 961.65 MPa and the elongation reaches 26.5%,showing excellent mechanical properties.