Influences of solute atoms and their contents on the uniform elongation were investigated using Al–Mg and Al–Si alloys respectively. Dislocation characteristics of both alloys were examined by X-ray diffractometry and transmission electron microscopy. In the case of solute concentration ranging between 0.3 and 1.6 (mass%), it was found that the increase of solute concentration caused the decrease of the uniform elongation for the case of Al–Mg alloys, whereas the increase of that for the case of Al–Si alloys. It was suggested that the solute Mg in aluminum caused a strong interaction on dislocation with comparison to the solute Si, which probably caused the large increase of dislocation density during the tensile deformation. It is considered that the solute Si has stronger effect of decreasing the stacking fault energy of the aluminum alloy than the solute Mg. Thus, as for Al–Si alloys, the increase of the work-hardenability and the uniform elongation may occur by retardation of the dynamic recovery during the tensile deformation.

Deformation behavior has been studied in a multifunctional beta titanium alloy, Gum Metal, using in-situ nanopillar-compression tests in transmission electron microscope in comparison with a conventional beta titanium alloy, beta III. In-situ observations for dislocation activity and phase transformation during compression test of solution treated samples have been performed in bright-field and diffraction modes. Distinct contrast of dislocations has not been observed during the tests in bright field mode, however subtle contrast change, which might be related to dislocation motion, has been observed in localized areas of the Gum Metal specimen. In the diffraction mode, pre-existing diffraction from omega phase decreased, and diffraction from alpha double prime phase increased with increase amount of plastic deformation. In addition, a pillar of Gum Metal with large length-to-thickness ratio showed a large amount of pseudoelastic deformation after unloading. These results have been discussed in relation to deformation mechanisms in these beta titanium alloys.

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.

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.