[21p-S322-1~9] 1.3 Novel technologies and interdisciplinary engineering

[21p-S322-3] Phase-field simulations of solidification patterns for varying the composition of an Al-Cu alloy

〇Yasushi Ogimoto¹, Keisuke Sato¹ (1.Fuji Electric)

Keywords:phase-field,Al-Cu alloy

Solidification patterns play a decisive role in designing mechanical properties of metal alloys. Since a grain coarsening would deteriorate the bonding strength of a joint part, we focus on the grain size of a theta-phase (Al₂Cu) in an attempt to utilize a eutectic bonding technique as a fabrication process for the joint of a heat exchanger by inserting a Cu pipe into an Al one (the eutectic temperature and composition are 548 ^oC and 17.5 mol% Cu, respectively). Thus it is of considerable importance to understand a grain coarsening process and to predict the grain size of the theta-phase as an indicator of brittleness. A simulation approach is useful for this purpose even starting from a simple model, though the composition of an Al-Cu liquid at the joint is not uniform and varies due to the diffusion from the Al and Cu pipes in a practical process.
Here we demonstrate the composition dependence of solidification patterns of an Al-Cu alloy such as dendrite and lamellar structures simulated with phase-field software MICRESS^®, together with the grain size of the theta-phase in hypereutectic compositions. The simulated results reveal that an abrupt grain coarsening of the theta phase occurs when the Cu concentration in the liquid phase exceeds 19 %, which could be a basis to simulate the practical fabrication process described above.