3-D multi-scale modeling of deformation within the weld mushy zone

Abstract

The deformation of the fusion weld mushy zone, as a critical factor in solidification cracking, has been simulated by combining a 3D multi-scale model of solidification and microstructure with a deformation model that includes the effects of solidification shrinkage, thermo-mechanical forces and restraining forces. This new model is then used to investigate the role of welding parameters on the deformation rate of micro liquid channels during Gas Tungsten Arc welding of AA6061. It is shown that the internal normal deformation rate due to solidification shrinkage and also the external normal deformation rate caused by external forces are both highest for the micro liquid channels at the center of the mushy zone where solidification cracks usually occur. Furthermore, the model shows that welding travel speed and welding current strongly influence the deformation rate of the weld mushy zone and consequently the solidification cracking susceptibility of the weld. The model can be also used to link micro-scale phenomena with the macro-scale characteristics of solidification cracking during welding.

Effect of weld travel speed on solidification cracking behavior. Part 3: modeling

“…Modeling these effects and their impact on solidification crack formation remains a difficult subject. Therefore, only multi-scale, multi-physics models, as the ones used to investigate weldability and solidification cracking behavior [85][86][87][88][89][90][91][92][93][94][95][96][97][98] [99,100], can efficiently simulate welding speed effect on solidification crack formation. Complex simulations to describe the travel speed effect must include modeling both microstructure and thermo-mechanical cells with the implementation of solidification cracking criteria.…”

“…The deformation of the fusion weld mushy zone, as a critical factor in solidification cracking, has been simulated by combining a 3D multi-scale model of solidification and microstructure with a deformation model that includes the effects of solidification shrinkage, thermo-mechanical forces and restraining forces [88]. This simulation focuses on AA6061 GTA welds.…”

“…Variation in AA6061 GTA welds for various welding parameters as a function of average solid fraction of (a) maximum cooling rate and (b) average internal deformation rate [88]. Captions indicate welding speed and current, e.g.…”

Dendritic Solidification and Physical Properties of Co-4.54%Sn Alloy with Broad Mushy Zone

“…Therefore, the phenomenon of solidification shrinkage and hot tearing is caused by thermal contraction, as the higher density of the solid driving the cracking process and hindered liquid flow prevents any void from being filled with liquid. Several defects, such as low fluidity, shrinkage porosity, heat cracking, segregation, and so on, take place inside this interval [1][2][3][4][5]. The rapid solidification of high undercooling is an effective method to avoid or eliminate these defects.…”

A generalised hot cracking criterion for nickel-based superalloys additively manufactured by electron beam melting

“…The fracture morphology accompanying ductility dip cracking exhibits a ductile intergranular fracture surface [20]. To understand how cracking occurs during AM processes, studies [14,19,[25][26][27][28] have referred to criterions developed by Rappaz et al [29] (RDG model) and Kou [30], which have been extensively applied to understand intergranular cracking during welding processes [31][32][33].…”