Process for producing high strength and high toughness aluminum alloy

A process for producing an aluminum alloy with a high strength and a high toughness, comprising the steps of:

• preparing an alloy blank having a primary structure which is one selected from a single-phase structure comprised of a solid-solution phase, a single-phase structure comprised of an amorphous phase, and a mixed-phase structure comprised of a solid-solution phase and an amorphous phase,
• subjecting the alloy blank to a thermal treatment at a temperature in a range of about 17K-36K below the destruction temperature of the primary structure, and
• maintaining the thermal treatment until an aluminum alloy is formed which has a secondary structure containing 20% or more by volume fraction Vf of chrysanthemum-shaped phases each having a diameter of at most 5 .mu.m and comprising a solid-solution phase and an intermetallic compound phase arranged radiately.