PURPOSE: To obtain the Al alloy material having sufficient strength and causing no strain to a product after artificial ageing treatment even if hardening after solution treatment is performed at a cooling velocity regulated to the extent as low as that of air cooling by limiting respective contents of Cu, Mg, Li, etc., and carrying out treatments under the prescribed process conditions.
CONSTITUTION: An alloy having a composition consisting of, by weight, 0.5 to 3.5% Cu, 0.5 to 4.0% Mg, 2.0 to 4.0% Li, further one or more kinds among 0.05 to 0.30% Zr, 0.05 to 0.30% Cr, 0.05 to 1.0% Mn, and 0.05 to 0.30% V, and the balance Al with inevitable impurities is melted and cast in an Ar atmosphere. The resulting ingot is subjected to homogenizing treatment and to plastic working by the ordinary method and further subjected to solution treatment at ≥500°C, to cooling at 1 to 5°C/sec cooling rate, and then to artificial ageing treatment, by which the above alloy material in which the average grain size of precipitates is regulated to ≤100nm can be prepared.
YOSHIDA HIDEO
HIRANO SEIICHI
