Effect of Melting and Solidification Behavior and Dendrite Morphology of DED Melt Pool on Tensile Strength
The unstable transient convection and heat transfer characteristics of the melt pool lead to a strong anisotropy in the mechanical properties of the deposited layer.In order to investigate the influence of deposited layer dendrite morphology on the difference of tensile property strengthening,a mesoscopic melt pool dynamics model oriented to heat-flow coupling is constructed and the transient convection and thermal characteristics of the melt pool from generation to quasi-steady state are investigated,and the solidification conditions such as temperature gradient and solidification rate near the solidification boundary of the melt pool are obtained.The predicted results of dendrite morphology induced by different solidification conditions along the solidification boundary are obtained by WBM phase field model,and the effects of changes in solidification conditions on the primary dendrite arm spacing,dendrite tip radius and dendrite tip subcooling are also investigated.The strengthening trend of dendrite morphology on the tensile strength of different parts of the deposited layer is revealed,and the results show that the difference between the tensile strengthening value induced by dendrite morphology reache 99 MPa at the bottom and the middle of the deposited layer,and then the strengthening mechanism on the tensile strength of the deposite layer was discussed in detail.It provides a theoretical basis for achieving adjustable and controllable tensile properties of single/multi-layer directed energy deposition.
directed energy depositiondeposited layermelt poolphase fieldmechanical properties
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