The size and distribution of ceramic particles in aluminum matrix composites have been reported to remarkably influence their properties. For a single ceramic particle, the particle size is too small and prone to agglomeration, which makes the mechanical properties of the composites worse. When the ceramic particle size is too large, the particles and alloy at the interface are not firmly bonded, and the effect of dispersion distribution is not achieved, which will also reduce the mechanical properties of the composites. The multi-size ceramic particles are expected to improve this situation, while their effect on hot workability is less studied. In this study, the hot deformation behavior, constitutive model, processing map and SEM microstructure were investigated to evaluate the hot workability of multi-size SiC particle-reinforced 6013 aluminum matrix composites. The results showed that the increased deformation temperature and decreased strain rate could decrease flow stresses. The flow stress behaviors of the composites can be described by the sine-hyperbolic Arrhenius equation with the deformation activation energy of Q = 205.863 kJ/mol. The constitutive equation of the composites is $\dot{\epsilon }=3.11592\times {10}^{13}{\left(\sinh \left(0.024909\mathsf{\sigma }\right)\right)}^{4.12413}\exp \left(-\frac{205863}{RT}\right)$. Then, the hot processing map of the SiCp/6013 composites was constructed and verified by SEM observations. The rheological instability zone was in the region of a high strain rate. The optimal processing zone for composites was 450~500 °C and 0.03~0.25 s⁻¹. In addition, the strain level was found to increase both the Q value and the area of the instability zone.

A hot compression test was conducted across a range of temperatures (350, 400, 450, and 500 °C) and varying strain rates (0.001–10 s⁻¹) to explore the hot compression behavior of the 6063 alloy. Hot processing maps were obtained based on the stress–strain curves. Optimal processing parameters were identified as residing within the intervals of (470–500 °C, 0.01–0.1108 s⁻¹), achieving a maximum dissipation efficiency of 0.4, which is of great importance for perfecting hot processing. The microstructure evolution was characterized using an optical microscope and a transmission electron microscope. The initial grains were elongated under compressive deformation, and the density of dislocation rose with increasing strain rate and decreasing temperature. Dynamic recovery serves as the main dynamic softening mechanism during hot compression.

The microstructures and mechanical properties of Mg–3Sn–0.1Ca–xMM (mischmetal, x = 0.3, 0.6, and 0.9 wt.%) alloys were investigated. Optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were used to characterize the microstructures and phase constitutions of the cast and rolled alloys. Room temperature tensile tests were conducted to obtain the mechanical properties and macro-textures to evaluate the texture weakening effect results of the MM. The results show that an abundance of second phase formed, confirmed as the (Ca,MM)MgSn phase, and the volume fraction increased with the increasing MM addition. The tensile yield strength of the as-cast alloys increased with the MM addition, but the elongation decreased. All of the rolled Mg–3Sn–0.1Ca–xMM alloys showed a strong basal texture, and only slightly decreased in intensity after annealing treatment due to the particle-stimulated nucleation of recrystallization. The as-annealed Mg–3Sn–0.1Ca–0.6MM alloys exhibited the highest tensile strengths of 266.5 ± 3.3 MPa and 136.1 ± 3.7 MPa, which are mainly ascribed to grain refinement strengthening, Orowan strengthening and texture strengthening.