Laser processing of thin-sheet rolled aluminum-calcium alloy of the Al–Ca–Cu–Mn–Zr system

Abstract

Laser processing of thin-sheet rolled aluminum-calcium alloy of the Al-Ca-Cu-Mn-Zr system was studied to model its structure and properties obtained during additive manufacturing. The primary structural components of the hypereutectic Al4Ca3Cu1Mn0.4Zr alloy (both as-cast and after laser remelting) include the (Al, Cu)₄Ca and Al₂₇Ca₃Cu₇ phases, with Mn and Zr remaining in the aluminum solid solution. Laser remelting of thin-sheet rolled products, which creates crystallization conditions that are typical for additive manufacturing (AM) processes, prevents the formation of undesirable primary crystals of the Al₂₇Ca₃Cu₇ phase and ensures the formation of a quasi-eutectic structure during crystallization. The typical structure consists of dendritic cells (~ 3–4 μm) surrounded by eutectic intermetallic phases (~ 200 nm), which is 10 times thinner than structural components formed during casting at a crystallization rate of 10 K/s. The hardness of the formed structure increases by 10% compared to the as-cast state. Alloys subjected to laser remelting (85 HV) demonstrate thermal stability of the structure and properties during prolonged isothermal annealing (100 h) at 350–400 °C. The maximum temporary decrease in hardness values does not exceed ~ 10% due to the difference in kinetic features of coarsening of eutectic intermetallic phases and breakdown of (Al), leading to precipitation hardening caused by the formation of Al₆Mn particles and Al₃(Zr) nanoparticles (L1₂ phase).