Effect of gradient structure of Al-Si-Cu-Ni alloy on bending properties
Al-Si-Cu-Ni gradient-structured alloys were prepared under different process parameters by varying the laser power during selective laser melting and forming,and the bending properties were tested under positive and negative pressure conditions.After optimizing the process parameters,the comprehensive mechanical proper-ties of the gradient-structured alloys were improved,the microstructures at different locations on the sides were observed,and the hardness distribution was tested.The results show that the bending properties under positive pressure conditions are better than those under counterpressure.With the increase of laser power,the microstruc-ture is gradually coarsened,the precipitation amount of Cu-rich and Ni second phases increases,and the Vickers hardness and Brinell hardness linearly decrease,which makes the alloy samples produce a gradient structure.The bending strength and fracture displacement of the gradient-structured alloys prepared under the optimal process parameters under positive pressure can reach(838±22)MPa and(0.93±0.04)mm,which are significantly higher than those of the homogeneous structure alloys((767±24)MPa,(0.85±0.03)mm),indicating that the gradient structure produces a toughening effect on the alloy materials,which is mainly attributed to the high strength of the fine-crystalline tissues,good plasticity of the coarse-crystalline tissues,and good plasticity of the coarse-crys-talline tissues.The synergistic effect of the gradient structure on the alloys is mainly attributed to the high strength of the fine-crystalline tissue and the good plasticity of the coarse-crystalline tissue.
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