The Effect of Ni Addition on the Phase Composition and Properties of Quasi-Binary Al-Cu-Y(Er,Yb,Gd) Alloys
摘要
The microstructure and phase composition in the as-cast and homogenized states, recrystallization behavior, tensile properties and electrical conductivity in the rolled and annealed states of the Al-Cu-Ni-Y(Er,Yb,Gd) alloys were investigated in details. The Ni substituted the Cu atoms in the crystal structure of the Al8Cu4REM and Al3REM phases as was demonstrated by scanning electron microscopy and x-ray diffraction analyzes. The intermetallic phases in the alloys were fragmentized, spheroidized and grew to about 1 µm size after 1 h of homogenization annealing at 585-595 °C. The REM and Ni have effect on the Al2Cu phase solvus and decrease significantly the volume fraction of the phase at 180-250 °C in the Al-Cu-Ni-REM alloys. The recrystallization behavior of the investigated alloys is different. Completely recrystallized structure was found in the AlCuNiEr alloy that confirmed by the lowest hardness after 1 h of annealing at 250 °C. The highest hardness was achieved in the AlCuNiGd alloy with lower fraction of the recrystallized microstructure. The alloys annealed at 150 °C for 1 demonstrate he the highest UTS of 252-273 MPa at the lowest elongation of 3-4.5% and 52.8-54%IACS. The best combination of the UTS (275 MPa) and electrical conductivity (53.5%IACS) was achieved in the AlCuNiGd alloy after 1 h of annealing at 150 °C. The 100 h of annealing at 250 °C slightly decreases the UTS to 138-143 MPa, and provide the highest elongation about of 29% and electrical conductivity of 57%. Investigated alloys demonstrate a good combination of tensile strength and electrical conductivity and can be base for developed novel alloy for high-temperature application.