Microstructures And Mechanical Properties Evolution Of An Al-0.74Fe-0.23Cu Alloy Processed By Repetitive Continuous Extrusion Forming

The processing of metals through the application of severe plastic deformation(SPD) has attracted much attention because of the potential for achieving remarkable grain refinement to the submicrometer or even, under some conditions, to the nanometer Range. Repetitive continuous extrusion forming process(R-Conform process), was performed on a horizontal continuous casting(HCC) Al-0.74Fe-0.23 Cu alloy.The wheel revolving speed were 5 rpm(0.52rad/s) and 21rpm(2.20rad/s),respectively. The microstructural evolution and mechanical properties of the Al-0.74Fe-0.23 Cu alloy under different deformation conditions were studied by optical microscope, Electron Back-scattering Patterns, X-ray diffraction, scanning electron microscope, transmission electron microscope, and tensile testing to discuss the possibility that taking R-Conform process as a continuous severe plastic deformation method and the effectiveness. The results show that:1. The microstructures of as-cast Al-0.74Fe-0.23 Cu alloy are different in grain size, morphology and crystal orientation distribution on transverse section and longitudinal section. Al Fe, Al Fe Si and Al Si phases are formed during horizontal continuous cast solidification processing.2. During R-Conform process at a low wheel revolving speed of 5 rpm, the first pass Conform process improves tensile strength and ductility of the HCC Al-0.74Fe-0.23 Cu alloy. While, further repetitive Conform processing leads to the decrease of strength and hardness, and the increase of elongation, which shows obvious work softening.3. During R-Conform process at the low wheel revolving speed of 5 rpm, the first pass Conform process induces the formation of fibrous microstructures, which shows that recovery is the main softening mechanism, while recrystallization may occur at late Conform passes with the accumulation of deformation. the first pass Conform process induces redissolution of some precipitations and dynamic precipitation of Al7Cu2 Fe. Meanwhile, the first pass Conform process lead to the change of crystal orientation distribution, the redistribution of eutectic phases. Further Conform deformation has little effect on the evolution of precipitation and the crystal orientation distribution of Al-0.74Fe-0.23 Cu alloy, but changes the distribution of precipitations, meanwhile, precipitations are broken with increasing Conform passes.4. The mechanical properties evolution of the Al-0.74Fe-0.23 Cu alloy during R-Conform process at a high wheel revolving speed of 22 rpm is similar to that when R-Conform process was conducted out at the low wheel revolving speed of 5 rpm.However, high speed R-Conform processing promoted the evolution process of mechanical properties.5. High speed R-Conform promoted the uniformly distributed behavior of precipitations, but did not promote the broken behavior. During the first pass Conform process at high speed, partial grains refinement occurred, which shows the occurrence of recrystallization. With the increase of Conform passes, the rate of recrystallization accelerated constantly, which led to the lower strength than that of low speed R-Conform. Besides, at the initial stage of R-Conform process at high speed, massive Shear bands(SBs) generated, so the formation of new grains generated at later Conform passes may be related to the SBs generated at the initial stage.