Strenghthening features of mechanically alloyed Al-Mn-Cu alloy

Abstract

Structure and mechanical property of mechanically alloyed granules of the Al–7.7Mn–3.1Cu (wt.%) alloy are studied after annealing in the temperature range of 250–450 °C and compaction at 400–450 °C. It is shown that a ball milling for 10 h provides for a formation of aluminum based supersaturated solid solution and Al₆Mn phase. Comparison of X‑ray structural data and differential thermal analysis and the change in granule hardness demonstrates the occurrence of recrystallization processes and decomposition of supersaturated solid solution with precipitation of Al₆Mn and CuAl₂ phases at heating. Compaction of granules at 400 °C provides a sample’s density of 2.87 g/sm³ and microhardness of 310±16 HV. Annealing of the compacts obtained at 400–450 °C leads to an increase in density and strength. Compaction at 450 °C increases the density of material to 3.01 g/sm³ and provides better mechanical properties according to compression tests results. The alloy exhibits yield strength of 910±10 MPa, ultimate tensile strength of 1060±20 MPa, deformation to failure of 0.9% at room temperature and an average value of yield strength of 287±20 MPa without microfailures after 40% of compression at 350 °C.