ALUMINUM ALLOY FORMED BY PRECIPITATION HARDENING AND METHOD FOR HEAT TREATMENT THEREOF

摘要

There is provided a precipitation hardening Al alloy in which an average area of eutectic structures existing in the Al alloy is less than 4 mu m2. This Al alloy contains 6.5 to 7.5% by mass of Si, 0.36% by mass or less of Mg and 20 to 70 ppm of Sr, and is preferably used as a vehicle wheel. In heat treatment method of the precipitation hardening Al alloy, a work piece is subjected to solution treatment by being made to exist in a fluidized bed, and further a rate of solid solutions of Si and/or Mg into alpha phase is made to be 60% or more in the solution treatment and aging treatment is carried out at temperatures from 150 DEG C or more to less than 200 DEG C. The precipitation hardening Al alloy to be obtained has well-balanced three mechanical properties of tensile strength, yield strength, and elongation, and is also excellent in fatigue strength. IMAGE