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Tensile tests and strain rate jump tests have been carried out at low temperatures (77 K $ room temperature (RT)) using pure Cu specimens that were severely deformed by accumulative roll bonding (ARB). The dependence of the flow stress on the temperature and the strain rate has been investigated and the strain rate sensitivity m and its variation caused by the change in the ARB cycle N are discussed. At RT, the strain rate sensitivity for N 4 stays at about 0.005. However, for N ! 5, m increases with increasing N to become $0:018 when N ¼ 8. The deformation mechanisms of the ARB processed Cu are discussed with the activation volume V Ã . The temperature dependence of V Ã and its variation with increasing N are also discussed.

Aluminum matrix composites having dispersoids of Al 3 Ti intermetallic compounds can be obtained by reaction centrifugal mixed-powder (RCMP) method. It is reported that Al 3 Ti intermetallic compounds act as grain refiners, since the disregistry value between Al 3 Ti intermetallic compound phase and Al matrix is smaller than 10%. In terms of lattice registry between Al matrix and Al 3 Ti phase, it is expected that the grain structure of Al matrix in Al-Al 3 Ti composites becomes more refined than that of centrifugally cast pure Al. In this study, Al-Al 3 Ti composites have been cast by the RCMP method. Effects of the Al 3 Ti phases around Ti particles formed by reaction between Al and Ti particles during RCMP method on grain refinement behavior of Al matrix have been systematically investigated. Moreover, grain refining performance of Al cast by Al-Ti refiner with grain shaped Ti particles was also studied.

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Origami, the ancient art of paper folding, has shown its potential as a versatile platform to design various reconfigurable structures. The designs of most origami-inspired architected materials rely on a periodic arrangement of identical unit cells repeated throughout the whole system. It is challenging to alter the arrangement once the design is fixed, which may limit the reconfigurable nature of origami-based structures. Inspired by phase transformations in natural materials, here we study origami tessellations that can transform between homogeneous configurations and highly heterogeneous configurations composed of different phases of origami unit cells. We find that extremely localized and reprogrammable heterogeneity can be achieved in our origami tessellation, which enables the control of mechanical stiffness and in-situ tunable locking behavior. To analyze this high reconfigurability and variable stiffness systematically, we employ Shannon information entropy. Our design and analysis strategy can pave the way for designing new types of transformable mechanical devices.