Influence of AlCuSc Ternary Phase on the Microstructure and Properties of 1469 Alloy

Abstract

Microstructure evolution and mechanical properties of a 1469 alloy and a Sc-free1469 type alloy were examined. SEM observation indicates that AlCuSc ternary phases (W) are formed after homogenization annealing, and cannot be dissolved during the following heat treatments. These coarse particles consume abundant Cu atoms from the Al matrix that are available for solutioning, which results in the decrease of precipitation of the T1 phase during aging treatment. The W phase has negative effects on the examined alloy’s mechanical properties. The tensile strength of Sc-added alloy is 40MPa lower than that of the Sc-free alloy. The formation of the W phase has a close relationship with Cu/Sc ratio, which shows the importance of controlling the concentration of Cu and addition of Sc. Formation of W phase suppress the effect of precipitation hardening of the T1 phase in high strength Al-Cu-Li alloys

Effect of Rolling Reduction on Microstructures and Mechanical Properties of Sc-Containing Al-3.2Cu-1.5Li Alloy

“…When Sc is introduced into Al-Cu-Li alloys with a low content of Cu or without Cu, the Sc atoms tend to combine with Al atoms to form A1 3 Sc particles wrapped by δ' (Al 3 Li) particles and exist as Al 3 (Sc, Zr) composite particles [14]. For some Al-Cu-Li alloys with higher Cu/Li ratios (Cu/Li > 2.8), such as 1469 [15,16], 2070 [17] and the new Al-3.8Cu-1.2Li alloy [18], the addition of minor Sc exerts some negative function on the strength. However, the improved hardness and strength are presented in the AA2195 alloy (Cu/Li = 3.3) with the addition of Sc, and the authors attributed this phenomenon to the refined grain and fine dispersed Al 3 (Sc, Zr) particles [19].…”