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The purpose of this paper is to investigate microstructure and properties of Sn3.0Ag0.5Cu-XAl₂O₃ composite solder which were prepared through powder metallurgy route.

Sn3.0Ag0.5Cu (SAC305)-XAl₂O₃ (X = 0.2, 0.4, 0.6, 0.8 Wt. %) composite solders were prepared through the powder metallurgy route. The morphology of composite solder powders which consists of Al₂O₃ particles and SAC solder powders after ball milling was observed. The retained ratio of Al₂O₃ nanoparticles in composite solder billets and solder joints were also quantitatively measured. Furthermore, the as-prepared composite solder alloys were studied extensively with regard to their microstructures, thermal property, wettability and mechanical properties.

After ball milling, the Al₂O₃ nanoparticles added were observed embedded into the surface of SAC solder powders. Only about 5-10 per cent of the initial Al₂O₃ nanoparticles added were detected in the composite solder joints after reflow. In addition, finer ß-Sn grains were achieved with addition of Al₂O₃ nanoparticles; the Al₂O₃ nanoparticles were found retained in the composite solder matrix. Besides, negligible changes in melting temperature and the considerably reduced undercooling were obtained in composite solder alloys. Wettability was improved by appropriate addition of Al₂O₃ nanoparticles. Microhardness and shear strength of composite solders were both improved after Al₂O₃ nanoparticles addition.

This paper indicated that powder metallurgy route offered a feasible approach to produce nanoparticle reinforced composite solder. In addition, the quantitative analysis of the actual retained ratio of the Al₂O₃ nanoparticles in solder joints provided practical implications for the manufacture of composite solders.

This paper aims to present a new topology method in designing the lightweight and complex structures for 3D printing.

Computer-aided design (CAD) and topology design are the two main approaches for 3D truss lattices designing in 3D printing. Though these two ways have their own advantages and have been used by the researchers in different engineering situations, these two methods seem to be incompatible. A novel topology method is presented in this paper which can combine the merits of both CAD and topology design. It is generally based on adding materials to insufficient parts in a given structure so the resulting topology evolves toward an optimum.

By using the topology method, an optimized-Kagome structure is designed and both 3D original-Kagome structure and 3D optimized-Kagome structure are manufactured by fused deposition modeling (FDM) 3D printer with ABS and the compression tests results show that the 3D optimized-Kagome has a higher specific stiffness and strength than the original one.

The presented topology method is the first work that using the original structure-based topology algorithm other than a boundary condition-based topology algorithm for 3D printing lattice and it can be considered as general way to optimize a commonly used light-weight lattice structure in strength and stiffness.