3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials

Jiazhou Wu,Hua Zhang,Yan Feng,Bingbing Luo

doi:10.3390/met8060443

Abstract

A three-dimensional multiphysical transient model was developed to investigate keyhole formation, weld pool dynamics, and mass transfer in laser welding of dissimilar materials. The coupling of heat transfer, fluid flow, keyhole free surface evolution, and solute diffusion between dissimilar metals was simulated. The adaptive heat source model was used to trace the change of keyhole shape, and the Rayleigh scattering of the laser beam was considered. The keyhole wall was calculated using the fluid volume equation, primarily considering the recoil pressure induced by metal evaporation, surface tension, and hydrostatic pressure. Fluid flow, diffusion, and keyhole formation were considered simultaneously in mass transport processes. Welding experiments of 304L stainless steel and industrial pure titanium TA2 were performed to verify the simulation results. It is shown that spatters are shaped during the welding process. The thickness of the intermetallic reaction layer between the two metals and the diffusion of elements in the weld are calculated, which are important criteria for welding quality. The simulation results correspond well with the experimental results.

Highlights

Dissimilar metal welding often confronts the problems of brittle intermetallic compounds, residuals stresses, and crack formations, which lead to lower joint performance
Thethickness of an intermetallic reaction layer is an important factor affecting the formation of intermetallic compounds, besides the differences in the physical and chemical properties of the materials
The rapid melting and solidification of metal can reduce the formation of intermetallic compounds in laser welding of dissimilar materials, which improves the mechanical properties of the welded joint

Summary

Introduction

Dissimilar metal welding often confronts the problems of brittle intermetallic compounds, residuals stresses, and crack formations, which lead to lower joint performance. Thethickness of an intermetallic reaction layer is an important factor affecting the formation of intermetallic compounds, besides the differences in the physical and chemical properties of the materials. As long as the thickness of the intermetallic reaction layer is maintained in the proper range, the welded workpiece will have good mechanical properties. Precise control of the heat source is highly important in the welding process. Compared with the traditional welding method, laser welding has several advantages such as precise energy control, high density due to minimal laser beam diameter, and narrow heat affected zones. The rapid melting and solidification of metal can reduce the formation of intermetallic compounds in laser welding of dissimilar materials, which improves the mechanical properties of the welded joint. Laser welding is an important joining method for dissimilar metals

Methods

Results

Conclusion