Effects of Mg Addition on δ^’ Precipitation and Mechanical Properties of Al-Li-Zr Alloys Containing Ti and/or V

抄録

Mechanical properties and precipitation structures of Al–Li–Mg–Zr alloys containing Ti and/or V were investigated. In our earlier work, the Al–3 mass%Li–0.2 mass%Zr–0.1 mass%Ti and the Al–3 mass%Li–0.2 mass%Zr–0.1 mass%V quaternary alloys have shown the magnificent mechanical properties due to the grain refinement and the fine precipitates which consist of both the metastable Al₃(Zr, Ti or V)-Al₃Li composite precipitates and δ^′(Al₃Li) precipitates. In this work, it was observed that, addition of magnesium from zero to 2 mass% in Al–3 mass%Li–0.2 mass%Zr–0.1 mass%Ti alloy or in Al-3 mass%Li–0.2 mass%Zr–0.1 mass%V alloy magnifies the proof and tensile strengths. The Al-3 mass%Li–1.0 mass%Mg–0.2 mass%Zr–0.1 mass%Ti alloy aged at 473 K for 4 h elongates 6–7% with high ultimate tensile strength about 520–540 MPa. But raising the magnesium content to 2 mass%, the elongation decreases to a value of about 4% with a significant increase in proof strength at the same age condition. It is verified that the magnesium content influences significantly the size and number density of δ^′ precipitates.