It is known that the susceptibility to stress corrosion cracking of Al–Mg alloy increase with increasing Mg content, whereas the strength of Al–10Mg alloy reach to that of 2000 and 7000 series Al alloys. In-situ observation of the stress corrosion cracking of a hydrogen charged Al–10Mg alloy was conducted by using synchrotron X-ray microtomography in SPring-8. The corrosion area and crack were observed in hydrogen charged material with water atmosphere. The corrosion and crack grow up with increasing applied strain. In addition, deformation localization and high hydrostatic strain that was caused by nucleation of nanovoids during deformation was also observed in crack tip. These observations indicated that the stress corrosion cracking of an Al–10Mg alloy occurs due to the influence of hydrogen.

Hot extruded AZ31F magnesium alloy was multi-directionally forged (MDFed) to 6 passes (a cumulative strain of ΣΔε=4.8) under decreasing temperature conditions, and then the specimens MDFed to 6 passes were annealed at temperatures ranging from 373 to 623 K. The as-MDFed specimen possessed a weak (0001) texture, whereas the MDFed specimen annealed at 623 K almost random orientation. Average grain size and hardness before and after static recrystallization indicated 0.6 µm and 85.1Hv, and 3.2 µm and 58.5Hv, respectively. The relationship between hardness (Hv) and grain size (d) in both as-MDFed and as-annealed specimens followed the Hall–Petch relation, which was expressed by a unified equation of Hv=38.7+36d ^−1/2。

Effects of Zr addition on the intergranular fracture of Al–Cu–Mg and Al–Zn–Mg–Cu alloys were investigated. The alloys were Al–4.6 mass%Cu–1.5 mass%Mg (−0.17 mass%Zr) and Al–7.5 mass%Zn–2.9 mass%Mg–2.0 mass%Cu (−0.2 mass% Zr). All alloys were synthesized using high-purity aluminum with more than 99.999 mass%. The grain size and hardness of each alloy were made consistent by annealing and further aging treatment, respectively. It was revealed that the Zr addition suppresses intergranular fracture and improves the ductility under the condition that the grain size and hardness are the same. These effects of Zr addition appeared near the transition region from transgranular fracture to intergranular fracture. The first-principles calculation results indicated that Zr is the only element which segregates to the grain boundary and strengthens the grain boundary among alloying elements of Zn, Mg, Cu, and Zr in aluminum.

Pure magnesium powders together with different amounts of process control agent (PCA) were mechanically milled (MM) using a planetary type of ball mill with different processing times. MMed powders were consolidated into bulk materials by the spark plasma sintering (SPS). Changes in hardness and solid-state reactions of the MMed pure magnesium powders and the bulk materials have been examined by hardness measurements and an X-ray diffraction (XRD). Morphology of the MMed pure magnesium powders was characterised by scanning electron microscopy (SEM). The Vickers microhardness of the pure magnesium powders increased from 38.9 to 52.5 HV after 32 h of MM time with 1.00 g of PCA due to the combination of strain induced and minimized crystallite size. The Vickers hardness of the bulk materials fabricated from 32 h MMed pure magnesium powders with 1.00 g of PCA exhibited 51.4 HV that is similar to that of AZ31-O.

In Al–Si based alloy sheets for brazing, the balance between brazeability and shape retainability is important. This study shows the influence of Mn contents and brazing conditions on the brazeability and the shape retainability during brazing. The brazeability was evaluated using a test piece called “reverse T shape” and the shape retainability was evaluated by a sagging test. The results showed that the brazeability was influenced by the equilibrium liquid phase fraction during brazing. Then, Mn contents and brazing conditions had little influence on the brazeability because these factors did not change the liquid phase fraction significantly. The results also showed that the shape retainability during brazing was much influenced by the addition of Mn. Due to the addition of Mn, many particles consisting of Al, Si, Mn and Fe were formed during sheet-manufacturing process and made grains coarser when recrystallization occur during brazing. Therefore, the addition of Mn was effective for improving the balance between the brazeability and the shape retainability.

To predict hot tearing of direct chill casting ingot, both the tensile constitutive behavior and elongation of alloy are inevitable during partial solidification. For predicting both the maximum true stress σ_ss and the elongation ε_elong regardless of alloy systems, their dominant factor was examined in terms of the solidification microstructure. For an Al–Mg and an Al–Cu alloys, (i) temperature T dependences of the maximum true stress and elongation (σ_ss=f(T) and ε_elong=f(T)) and (ii) dihedral angle θ of liquid phase formed at grain boundary were measured experimentally. Then, fraction of solid cohesion C was determined by the Campbell’s model using the angle. Firstly, the solid fraction dependence of the tensile properties (σ_ss=f(f_s) and ε_elong=f(f_s)) were compared between the two alloys. The two dependences differ with each other. Secondly, the fraction of solid cohesion dependences of the tensile properties (σ_ss=f(C) and ε_elong=f(C)) were compared and the result shows that the two dependences were consistent with each other. The fraction of solid cohesion enables to explain the difference in solid fraction dependence of the tensile properties for the two alloys. The result demonstrates that the dihedral angle should be essential to predict the two tensile properties of alloy during partial solidification.