|About this Abstract
||2019 TMS Annual Meeting & Exhibition
||Solidification Processing of Light Metals and Alloys: An MPMD Symposium in Honor of David StJohn
||Simulating the As-cast Microstructure of an Al-2Cu Alloy Formed under Ultrasonic Treatment
||Gui Wang, Paul Croaker, Matthew Dargusch, Damian McGuckin, David StJohn
|On-Site Speaker (Planned)
To investigate acoustic streaming and its effect on microstructure formation during a casting process under Ultra-Sonic Treatment (UST), a computational model was developed to couple the fluid flow, heat transfer, nucleation and grain growth. The model successfully describes hydrodynamic fields generated by ultrasonics and its influence on formation and evolution of the microstructure of an Al-2Cu alloy. The influence of the duration of UST and the associated acoustic streaming on convection and the resulting temperature distribution, nucleation and grain growth was investigated using this model. A key feature of UST is the application of a relatively cold sonotrode for a certain period of time during the solidification stage of the UST. The modelling revealed that the use of a sonotrode created a casting environment that not only promoted crystal nucleation but also enabled their growth and survival during transport of these grains into the bulk of the melt by strong convection. The enhanced convection established a low temperature gradient throughout the melt which favours the formation of an equiaxed grain structure. To achieve the most refinement, UST should be applied until the coherency point, a solid fraction of 21%, of the Al-2Cu alloy is reached. Once past this coherence point, UST does not contribute to grain refinement since no acoustic streaming can be generated. The simulation of the effect of ultrasonic termination prior to this point indicates that the duration of UST predefines the grain density.