Aluminum alloy formed by precipitation hardening and method for heat treatment thereof

Abstract

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 mum2. 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 a 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.

Description

Technical field [0001] The invention relates to a precipitation hardening type Al alloy and a heat treatment method thereof. Background technique [0002] As casting materials such as castings, die castings, and aluminum (Al) alloys for elongation materials, Al-Si-based Al alloys containing several wt% of Si in Al are known, and Al-Si-based Al alloys are generally used. As a basic component, a multi-element Al-Si alloy containing other elements such as Cu and Mg. This is because, in the casting of casting materials such as castings, die castings, and ductile materials, the fluidity of the molten metal, the filling of the mold, etc., which are very important characteristics, are better than other alloys, and casting cracks are hardly caused. By combining with other elements, an alloy with high strength and expansion ratio, low thermal expansion coefficient, good wear resistance, etc. is obtained. [0003] As alloys with a small amount of Mg added to Al-Si alloys, there are AC4A, A...

AI Technical Summary

Problems solved by technology

[0007] In addition, in the heat treatment method using the atmospheric pressure furnace of the prior art, the temperature rise rate to the solution annealing temperature is slow, and the temperature rise takes time, and the solution annealing is performed at the solution annealing temperature for more than 3 hours, so there is The problem that the whole time of solution annealing needs to be spent more than 4 hours, and the inventors have found through research that, as mentioned above, when the solution annealing temperature is kept at the temperature for more than 3 hours, there is a coarsening of the eutectic structure, and the Al alloy The problem of greatly reduced strength and ductility

Images