10:15 AM - 10:30 AM
[14a-D63-5] Phase-field simulations of theta-phase grains solidified at Al-Cu eutectic interfaces
Keywords:phase-field, Al-Cu alloy, eutectic bonding
A eutectic bonding is a useful technique to fabricate the joint of a heat exchanger by inserting a Cu pipe into an Al one. It is, however, necessary to understand how the conditions such as temperature and time of a eutectic bonding process would influence on the solidification of theta-phase (Al2Cu) grains at Al-Cu interfaces, since the grain coarsening is an indicator of brittleness. A phase-field simulation is a powerful handle to examine a solidification process and to predict the grain size of alloys. Indeed, we have simulated the composition dependence of solidification patterns of an Al-Cu alloy with phase-field software MICRESS®, investigating the size of the theta-phase grains in hypereutectic compositions. In order to simulate the practical fabrication process, a reaction-diffusion model should be taken into consideration: the composition of an Al-Cu liquid at the joint varies due to the diffusion from Al and Cu pipes.
Here we report a solidification of theta-phase grains solidified at Al-Cu interfaces simulated with MICRESS® based on the reaction-diffusion model. Note that this model allows us to describe two processes: (1) a composition gradient in the Al-Cu liquid phase between Al and Cu pipes, and (2) a modified solidification path due to the diffusion from the Cu-pipe. Firstly, we have concentrated on the simulation of an anisotropic grain arising from the tetragonality by adequately choosing interface mobility, interface energy, and diffusion constant, respectively. Then we simulated temperature dependence of the size of theta-phase grains (T=570~610 oC, t_hold=0.7 sec), which well reproduces the overall trend obtained from the cross-sectional optical observation at the interfaces. In addition, a simulation on the time dependence of the size of theta-phase grains reveals that the process time after inserting a Cu pipe is a key factor to suppress the grain coarsening, because it directly relates to the amount of Cu content due to the diffusion from the Cu pipe. These results demonstrate that the phase-field simulations are really helpful to determine the process condition of the Al-Cu eutectic bonding .
Here we report a solidification of theta-phase grains solidified at Al-Cu interfaces simulated with MICRESS® based on the reaction-diffusion model. Note that this model allows us to describe two processes: (1) a composition gradient in the Al-Cu liquid phase between Al and Cu pipes, and (2) a modified solidification path due to the diffusion from the Cu-pipe. Firstly, we have concentrated on the simulation of an anisotropic grain arising from the tetragonality by adequately choosing interface mobility, interface energy, and diffusion constant, respectively. Then we simulated temperature dependence of the size of theta-phase grains (T=570~610 oC, t_hold=0.7 sec), which well reproduces the overall trend obtained from the cross-sectional optical observation at the interfaces. In addition, a simulation on the time dependence of the size of theta-phase grains reveals that the process time after inserting a Cu pipe is a key factor to suppress the grain coarsening, because it directly relates to the amount of Cu content due to the diffusion from the Cu pipe. These results demonstrate that the phase-field simulations are really helpful to determine the process condition of the Al-Cu eutectic bonding .