Cu composite materials was systematically summarized. • Graphene/Cu systems present an excellent electrical conductivity and increasing Debye temperature compared with pure Cu. • Compared to copper, the tensile strength of graphene/Cu composites are enhanced by 174% and 162% in parallel to the direction of graphene. • Strengthening and toughening effects of graphene in composites is originated from strain strengthening and load transfer.

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To reduce the precipitation of σ phases and to improve the hot workability of S31254 steels, boron has been added into the composition of S31254 to a concentration of 40 ppm. The precipitation behavior was investigated before and after the addition of boron in different S31254 alloys during the compression deformation, and the nose temperature at 950 • C and the phase dissolution temperature at 1074 • C were selected as the measurement temperature. The result showed that more σ phases were precipitated at the grain boundary of S31254 alloys, compared to the boron-added alloy. Meanwhile, the addition of 40 ppm boron into the alloys has obviously prevented the σ phases from the austenitic matrix, and it takes longer time for the precipitation of σ phase at 950 • C. The specific influence factors of boron on the precipitation of σ phases were also further discussed.

The second phases in the S31254 super austenitic stainless steel is easily precipitated, and the solution treatment plays an important role on the microstructure and performance. In this work, the solution treatment is performed on S31254 steel at 1180, 1200, and 1220 C for 1, 2, and 4 h, respectively. Given the grain size and precipitation of second phase, the 1200 C for 4 h or 1220 C for 2 h may be suitable as the solid-solution parameters. The corrosion resistance and impact toughness of the steel after solution treatment at 1200 C are further investigated by means of microstructural analysis and electrochemical experiments. The sample after solution treatment for 4 h, where no second phase can be observed, exhibits a lower corrosion rate and a better mechanical properties, compared to that after annealed for 1 or 2 h. The electrochemical impedance spectroscopy, Mott-Schottky, and XPS results indicate that the passive films of the samples, with a significantly decreased donor and acceptor densities and increased Cr 2 O 3 and Mo-riched oxides, may be responsible for the improvement of corrosion resistance. The impact toughness results show that the samples after solution treatment for 4 h has the highest impact energy among the studied samples.

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