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Aluminum foam sandwich structure is a new type of composite material with excellent mechanical and functional properties. As it is known that properties of aluminum foam sandwiches (AFS) vary if the foam core is sandwiched between different face sheets. To study the effects of face-sheet materials on the mechanical properties of AFS and enable a better understanding of the usage of such AFS structures under flexural load, AFS sandwiched by 6061-aluminum alloy face-sheets and 304 stainless steel face-sheets were fabricated and investigated under three-point bending by using WDW-T100 electronic universal tensile testing machine. Results showed that 6061-aluminum alloy reinforced AFS had the same peak load value with 304-stainless steel reinforced one almost so long as the thicknesses of the face-sheet material were the same and the foam core densities were the same too, but the energy absorption ability of 304-stainless steel reinforced AFS was much higher than that of 6061-aluminum alloy reinforced. However, the integrality of the 6061-sandwiched AFS was better than 304-sandwiched AFS. Deformation modes of the two types of AFS were also discussed in the present study.

The high strength low alloy steel's (HG785D) welded joint was formed by strength match under MAG (80% Ar +20% CO2). The microstructure, micro-hardness and fatigue crack growth rate of the parent metal, weld and heat affected zone were tested and analyzed. The results show that the heat affected zone's hardness is highest and the parent metal's hardness is lowest; Different part of the butt joint's fatigue crack propagation rate is different at the same stress ratio, the heat affected zone's fatigue crack propagation rate is the fastest while the weld joint is the lowest. And through the analysis of fatigue fracture and the weld microstructure from the parent metal to the weld joint, the reason why different part's fatigue crack growth rate is different is that their metallographic microstructure is different. Chinese library classification: TG407.

In order to improve the microstructure and mechanical properties of High Speed Steel (HSS), electromagnetic stirring method is adopted to enhance the solidification of target materials in this paper. The results show that optimization of the microstructure, refinement of the grain, reducing in segregation of the alloy elements, and improvement of the comprehensive properties of HSS can be obtained by the electromagnetic stirring through changing the morphology and distribution of the carbide.