The effect of equal-channel angular pressing (ECAP) at various temperatures (310, 330, and 350 °C) on precipitations and strengthening mechanisms of Mg–9Al–1Si alloys was investigated. The results indicated that the average grain size decreased gradually with decreasing of ECAP temperature. The distribution of the Mg2Si phase changed a little when the ECAP temperature increased. However, the different morphologies of β-Mg17Al12 phase were observed, including continuous and uncontinuous precipitation of particles at 310 and 350 °C. The continuous β-Mg17Al12 phase was hardly found and the refined β-Mg17Al12 phase was distributed dispersedly in the matrix at 330 °C. Thus, the mechanical properties of the Mg–9Al–1Si alloy was optimum: ultimate tensile strength and elongation were ∼350.8 MPa and ∼14.77%, respectively. It can be deduced that both grain refinement strengthening and precipitation strengthening play significant roles in strength increment of the alloy during the ECAP process. However, precipitation strengthening is the predominant mechanism.

An Al–3% B master alloy has been subjected to equal channel angular pressing (ECAP). The grain refining performance and fading resistance of an Al–3% B master alloy on a commercial purity Al (CPA) have been evaluated. The effect of the number of ECAP passes on the size and the distribution of the AlB2 particles, the grain size of CPA ingots with and without adding the Al–3% B master alloy subjected to ECAP have been investigated. The mean size of AlB2 particles was significantly reduced from ∼34 to ∼12 μm after four ECAP passes. Fine blocky AlB2 particles were uniformly distributed in the Al matrix. It has been revealed that when it was inoculated by the Al–B master alloy subjected to ECAP, the grain size of α-Al was decreased from ∼1200 to ∼180 μm after four ECAP passes, beyond that, the grain size tends to be saturated. It has been proved that grain refinement efficiency and fading resistance of the Al–3% B master alloy subjected to ECAP in CPA ingots was enhanced.

Pure Cu was made ultrafine-grained by equal channel angular pressing on route BC at ambient temperatures and deformed in situ in a scanning electron microscope at the elevated temperature of 373 K and at a constant total strain rate of 10−4 s−1. Deformation was repetitively stopped to take micrographs of the grain structure on the same area of observation, revealing limited activity of discontinuous dynamic recrystallization. During the stops of deformation, the flow stress was relaxing. The relaxation of stress as function of time was used to determine the rate of inelastic deformation as a function of stress, from which the activation volume ${V^ * }$ of the thermally activated flow was derived. It is found that the normalized values of ${V^ * }$ were lying in the same order generally found for coarse-grained pure materials. This seems to be in conflict with the literature. However, the conflict is resolved by noting that the literature results refer to quasistationary deformation with the concurrent dynamic recovery in contrast to the present results obtained at a virtually constant microstructure. The interpretation of the two kinds of activation volumes for thermally activated flow is discussed.

This study investigated the effects of 1 wt% SiC nanoparticles addition on the microstructures and mechanical properties of Mg9Al–1Si (wt%) alloy subjected to equal channel angular pressing (ECAP). Results showed that addition of SiC nanoparticles could refine matrix grain, Mg17Al12 and Mg2Si phase of as-cast alloy, but the Mg17Al12 phase still exhibited network structure and the morphology of Mg2Si phase was still Chinese-script type. During the ECAP process, network Mg17Al12 and Chinese-script shaped Mg2Si phases were partially broken down into fine particles (∼10 µm) and much finer particles (∼2 µm) respectively. In particular, these Mg17Al12 and Mg2Si particles were uniform distribution in ECAPed Mg9Al–1Si–1SiC composite. The well-distributed particles and the existence of SiC nanoparticles could promote the formation of fine DRXed grains through enhanced grain boundary pinning. During tensile testing at room temperature, ECAPed Mg9Al–1Si–1SiC composite exhibit optimal mechanical properties, the ultimate tensile strength and elongation to failure were reached to 255 MPa and 7.9%, respectively. Furthermore, at elevated temperature of 150 °C, the tensile strength and elongation to failure were considerably increased compared to an ECAPed, SiC-free Mg9Al–1Si alloy.