The parent patent described a process for producing a worked prod. with an isotropic structure in an Al alloy. In this patent of addn. a process is described for having the critical cooling rate for worked prods. in Al alloys mentioned in claims 1 and 2 of the parent patent. The prods. are held at a temp. Tt which is greater than the solidus temp. T1 but below the liquidus temp. T2 of the alloy for 1/2-12 hr. A redn. in the critical cooling rate allows an increase in thickness of the quenched parts for the same mechanical props. in the centre. A less powerful quenching medium than cold water, e.g. boiling water, can be used and residual quenching stresses are reduced which obviates the need for stress-relief treatment of the rolled prods. Large workpieces can be air-cooled (0.5 degrees C/sec) instead of water quenched without an obvious loss in mechanical props.
展开▼
