Study of the effect of calcium on structure, physicomechanical and technological properties of deformable alloy Al-3%Mg-0.8%Mn

Abstract

In this work the effect of 2% calcium on the structure, deformability and physicomechanical properties of Al-3%Mg‑0.8%Mn alloy is investigated. A hot rolling temperature of 400 °C for the alloy with calcium without prior homogenization appeared to be low, resulting in cold rolled sheets containing multiple defects, in contrast to a refrence alloy without calcium. During homogenization annealing at 550 °C aluminum-calcium eutectic is highly fragmented, which facilitates rolling. Evaluation of alloy with calcium resistance to recrystallization shows that hot-rolled sheets begin to lose strength after 250 °C, while for cold-rolled sheets this temperature is limited to 200 °C. Cold-rolled sheets of Al-3%Mg‑0.8%Mn alloy also have a temperature for the start of recrystallization of 250 °C, which is associated with liberation during hot rolling of nanosized dispersoids of Al₆(Mn, Fe) phase, which as a result of heterogenization at 550 °C have micron sizes. At the same time, cold-rolled sheets with added calcium have higher hardness and yield strength after one-hour annealing at 400 °C (71/61 HV and 124/107 MPa). Relative elongation is also better for alloy with added calcium. It is also shown that calcium addition increases corrosion current density from 0.71·10⁵ to 0.92·10⁵ A/m², while its value remains at the level for AMg5 alloy or grade 5182 alloy.