The effect of backpressure on the structure and mechanical properties of the Al-5 wt % Fe alloy produced by equal-channel angular pressing

The role of backpressure (from 40 to 275 MPa) and the number of passes upon severe plastic deformation (SPD) by the method of equal-channel angular (ECA) pressing using the brittle cast Al-5 wt % Fe alloy unhardenable by heat treatment. ECA pressing at room temperature made it possible to obtain an ultrafine-grained (UFG) structure with grain sizes of 325-450 nm and to enhance the strength properties of the cast alloy by a factor of 2-3. It has been shown that the increase in the magnitude of the backpressure to 275 MPa leads to a decrease in the grain size and a refinement of intermetallic particles, the formation of a supersaturated solid solution of iron in the Al matrix, and an enhancement of thermal stability, microhardness, strength, and plasticity of the deformed alloy. ECA pressing shifts the alloy unhardenable by heat treatment into the class of aging alloys, and the artificial aging at 175 degrees C enhances the strength properties of the alloy due to the precipitation strengthening. The increase in backpressure slows down crack formation in intermetallic particles and increases deformability in the process of ECA pressing.