Structure and Properties of New Heat-Resistant Cast Alloys Based on the Al–Cu–Y and Al–Cu–Er Systems

The microstructure and mechanical properties of new high-temperature casting aluminum alloys Al–5.6Cu–2.0Y–1Mg–0.8Mn–0.3Zr–0.15Ti–0.15Fe–0.15Si and Al–5.4Cu–3.0Er–1.1Mg–0.9Mn–0.3Zr–0.15Ti–0.15Fe–0.15Si are investigated. In an alloy with yttrium, modification with titanium gives rise to a decrease in the grain size from 190 to 40 μm, while the grain size in an alloy with erbium is 25 μm. Regarding the casting properties, the alloys are comparable to silumins alloyed with copper and magnesium. The greatest strengthening effect after quenching is achieved with aging at 210°C; the hardness is 130–133 HV. The tensile yield point at room temperature is 303–306 MPa with a relative elongation of 0.4%. At elevated temperatures of 200 and 250°C, the yield stress decreases to 246–250 and 209–215 MPa, and the elongation increases to 3 and 4–5.5%, respectively. The long-term strength retention after 100 h exposure to 250°C is 117–118 MPa. The presence of a solid solution that is sufficiently alloyed and strengthening dispersoids of the Al₃(Zr,Er), Al₃(Zr,Y), and Al₂₀Cu₂Mn₃ phases and the Al₈Cu₄Y, (Al,Cu)₁₁Y₃, (Al,Cu,Y,Mn), Al₈Cu₄ErAl₃Er, and (Al,Cu,Er,Mn) phases of crystallization origin in new alloys provide high levels of heat resistance.