Influence of intense plastic straining on grain refinement, precipitation, and mechanical properties of Al-Cu-Li-based alloys
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Grain refinement is one of the major interests when an ultrahigh strength/ductility combination is demanded for ambient and cryogenic temperature applications, especially when superplastic forming (SPF) is involved for the manufacturing of different aerospace structures. Equal-channel angular extrusion (ECAE) is a relatively new metalworking process, which is capable of producing an ultrafine, submicron-grained (SMG) structure by means of intense plastic straining without a change in the shape or dimensions of the worked material. In the current research work, the influence of ECAE processing on the room-temperature mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloys in the T4 and T6 temper conditions is investigated. An ultrafine SMG structure of 0.2 to 0.4 m was produced for the ECAE-processed alloys from an initial grain size of > 100 m, which is compared with a conventionally processed superplastic Weldalite sheet material with an 1.5 m grain size. The ECAE processing eliminates the precipitation-free zones (PFZs) in the T6 temper condition without the need for prior stretching. A significant improvement in the mechanical properties at room temperature is achieved by ECAE processing in comparison with conventional processing.
