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A novel medium-to-high strength aluminum alloy Al-6Mg-0.7Zr was prepared by using the rapid solidification-powder metallurgy process. The mechanical properties and microstructural changes of the annealed alloy were analyzed and studied through the methods，such as room temperature tensile testing，high temperature tensile testing，SEM and TEM. The results indicate that by using the rapid solidification-powder metallurgy method，the maximum solid solubility of Zr in the Al matrix is exceeded，and the successful preparation of a 0.7% Zr（mass fraction） alloy is achieved. The Al3Zr particles precipitated during the annealing process exhibit a coherent relationship with the matrix，contributing to the strength enhancement of the alloy. The nano-scale Al3Zr particles play a significant role in improving the strength of the Al-6Mg-0.7Zr alloy. At room temperature，the tensile strength of the Al-6Mg-0.7Zr alloy reaches 445 MPa，with the yield strength of 338 MPa and the post-fracture elongation of 20.10%. In addition，Al3Zr particles remain stable at high temperatures and exhibit significant hindrance to grain boundary migration and dislocation movement，thus providing the alloy with excellent high-temperature performance within temperatures below 200 ℃. At 150 ℃，the tensile strength of Al-6Mg-0.7Zr alloy reaches 320 MPa，the yield strength is 266 MPa and the elongation after fracture is 33.37%.

The influence of solid solution treatment on microstructure, tensile properties and residual stress of AlSi10Mg alloy prepared by selective laser melting was investigated by optical microscope, field emission scanning electron microscope, transmission electron microscope, tensile tests and Raman spectrometer. The results indicate that the as-built alloy has a fine microstructure and high strength, but there is obvious anisotropy and significant residual tensile stress. Both the ultimate tensile strength and the yield strength can be improved significantly by direct artificial aging treatment for as-built alloy. However, the morphologies of molten pools and eutectic silicon of aged alloy are as basically same as that of as-built alloy. The solid solution treatment can remarkably improve the anisotropy of microstructure and tensile property, and completely eliminate the residual tensile stress. Meanwhile, it also leads to structural coarsening, resulting in the ultimate tensile strength and yield strength are only about 50% of as-built alloy. For the solid solution treated alloy, there is no obvious change of microstructure, anisotropy and residual stress after artificial aging treatment. The ultimate tensile strength and yield strength reach 330 MPa and 270 MPa respectively, with the elongation after fracture about 10%-11%. The improvement of strength after artificial aging treatment is attributed to the precipitation of GP zone.

AlMg4.5Sc0.55Mn0.5Zr0.2 alloys were fabricated by selective laser melting.The effects of artificial ageing parameters on Vickers hardness of the alloy were investigated. The room temperature tensile properties and microstructures of as-built and optimized artificial ageing treated alloys were analyzed. Results indicate that the Vickers hardness of the alloy increases from 102HV to more than 140HV by artificial ageing treatment. As the rising of ageing temperature, ranging from 305℃ to 335℃, or prolongation of the ageing duration, from 1.5 h to 48 h, Vickers hardness presents increasing first, then decreasing and finally trends to be stable. The room temperature tensile properties of the alloys aged at 315℃ for 3 h or 12 h are almost equal, and there is no obvious anisotropy. The ultimate tensile strength and yield strength reach 470 MPa and 410 MPa respectively, with elongation of about 15.0%.The improvement of mechanical properties is due to the dispersion precipitation of nano-reinforced particles Al3(Sc, Zr), which possess a coherent interface with the matrix during artificial ageing.

The AlSi10Mg powder was prepared by supersonic gas atomization. After classified, the powder was fabricated into block by selective laser melting (SLM). The microstructure, phase, and evolutions of powder and block were investigated by optical microscope, scanning electron microscope and X-Ray Diffraction. The tensile properties of SLM block were tested by tensile experiments at room temperature. The results show that the size distribution of AlSi10Mg powder after classified can meet the requirements of SLM technology. The powder always is spherical and spherical-like. Meanwhile, the microstructure of powders is fine and uniform, which contain α(Al) matrix and (α+Si) eutectic. In addition, the melt pool boundaries of SLM block are legible. The microstructure is also uniform and densified, the relative density approaches to 99.5%. On the other hand, only α(Al) and few Silicon phase are detected in this condition, due to the most alloying elements are dissolved in α(Al) matrix. At room temperature, the ultimate tensile strength of SLM block reaches up to 442 MPa.

Preparation of duplex coating is an innovative way to improve components surface in terms of mechanical and tribological properties by the combination of high velocity oxy-fuel (HVOF) and physical vapor deposition (PVD) technologies. The present work focused on the construction, mechanical properties and high temperature tribological behaviors of the duplex coating consisting of a thick HVOF Cr3C2-NiCr interlayer and a thin PVD TiN top layer, as well as compared it with the Cr3C2-NiCr coating and the single TiN film. The results showed that the Cr3C2-NiCr/TiN duplex coating exhibited higher hardness, elastic modulus, H/E and H3/E2 ratios and superior load-bearing capacity than the single TiN film. The introduction of Cr3C2-NiCr intermediate layer did not affect the microstructure of TiN film but significantly improved the adhesion strength between TiN film and substrate, as well as the wear resistance sliding against WC ball at different temperatures. In addition, the friction and wear mechanism of the Cr3C2-NiCr coating, TiN film and Cr3C2-NiCr/TiN duplex coating was revealed by investigating the friction-induced morphological and structural evolutions of the sliding surface at elevated temperature. [ABSTRACT FROM AUTHOR]