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The low hardness and poor wear resistance of titanium alloy severely restrict its service life under friction conditions. Wear-resistant and self-lubricating coatings prepared on titanium alloy surface by laser cladding technology can greatly improve its wear resistance. In this paper, firstly, the influences of laser cladding technology(laser power, scanning velocity, spot diameter, specific energy, post-heat treatment, high frequency vibration, etc.) on the wear resistance of the coatings were reviewed. And then, the characteristics of different types of hard phases, matrix phases and self-lubricating phases as well as their influences on the wear resistance of the coatings were discussed. Finally, the wear-resistant and self-lubricating coatings prepared on the surface of titanium alloy by laser cladding were summarized and prospected.

2024-T4 aluminium alloy and pure copper were welded by submerged friction stir welding (SFSW) and the effect of rotation speed on microstructure and mechanical properties of SFSW joints was studied. The results indicate that the SFSW joint is well formed, without cracks, holes and other defects. With the increase of rotation speed, the surface of the SFSW joint is smooth and the smoothness is improved. Meanwhile a large number of copper is involved in the nugget zone (NZ), and the structure in NZ is gradually disordered; the forced cooling effect of water effectively inhibits the formation of grain coarsening and brittle intermetallic compound during SFSW; the tensile strength of joint is 227MPa, which is 70.3% of the tensile strength of the copper base metal(BM) at the rotational speed of 750r/min and the tensile strength and elongation of the SFSW joint decrease with the increase of rotation speed.

A Ti-50. 7% Ni (atomic fraction) shape alloy was prepared by vacuum induction melting under dynamic argon atmosphere. By analyzing the composition, deformation temperature, microstructure, and hardness of the as-cast Ni-Ti shape alloy in this study, it was found that the properties of the as-cast Ni-Ti alloy met the medical standard. To analyze the variation law of the flow stress, the flow stress of the compression deformation for as-cast Ni-Ti alloy was studied by high-temperature compression with a Gleeble-3800 simulated machine within a deformation temperature range of 750-950 ℃, strain rate range of 0. 001-1. 0 s-1, and strain level of 0. 5. To analyze the relationship between variables in the hot deformation process of as-cast Ni-Ti alloy, a constitutive equation based on dynamic material model was established. To determine the reasonable range of hot working conditions for as-cast Ni-Ti alloy deformation, hot processing maps under different hot deformation conditions were set up. The results show that when the deformation temperature decreases or strain rate increases, the flow stress of as-cast Ni-Ti alloy increases. This phenomenon shows that the main factors affecting the flow stress of as-cast Ni-Ti alloy are deformation temperature and strain rate. When the strain rate is 1. 0 s-1, the true stress-true strain curves of as-cast Ni-Ti alloy exhibits a zigzag feature. This is mainly attributed to the alternation between hardening and softening during deformation. According to the hot processing maps under different hot deformation conditions, the processing zone and unstable hot deformation region of the as-cast Ni-Ti alloy were obtained. Then, the best temperature range of hot deformation is determined as 820-880 ℃, and the true strain rate is less than 0. 1 s-1. This study provides a theoretical and data basis for the development of forging process parameters of Ni-Ti alloy.

Underwater friction stir welding (FSW) on 7A04-T6 aluminum alloy plates was carried out, and the effect of rotation rate on microstructure and mechanical properties of joints was investigated. The results show that the minimum hardness of underwater FSW joints is located in the thermo-mechanically affected zone. The hardness of welded joints at the high rotation rate of 950r/min exhibits W-shaped distribution, and the average hardness value in the nugget zone is higher than that of welded joints at the low rotation rate of 475, 600, 750r/min. When the rotation rate increases from 475r/min to 750r/min with a constant welding speed of 235mm/min, the precipitated phases in the nugget zone gradually become coarse, and the ultimate tensile strength coefficient of the joint decreases from 89.71% to 82.33%; when rotation rate increases to 950r/min, the precipitated phases dissolve into aluminum matrix during welding, and age after welding. This produces the fine and homogeneous dispersed phases, which results in an increase of the strength coefficient to 89.04% and a certain enhancement of strain hardening capacity and elongation for the joints. All the tensile fracture surfaces exhibit the mixed characteristics of microporous polymerization and cleavage fracture.

7A04 aluminum alloy plate was jointed by submerged friction stir welding(SFSW), and welded joints were treated (Post Weld Heat Treatment, PWHT), and the effect of post weld heat treatment on the microstructure and mechanical properties in SFSW was investigated. The results show that PWHT joints exhibit dispersively distributed fine precipitates phase morphology, are significantly superior than the feature of the small amount of precipitates with dispersed distribution in SFSW joints. Compared with SFSW joints, the mechanical properties of joints are improved significantly by PWHT. The average hardness of the weld joints nugget zone is increased by 39.7HV, and the tensile strength is increased by 67MPa, reaches 96.1% of the base material, strain hardening capacity of the joints is also enhanced, the tensile fracture exhibits mixed fracture feature of microporous polymerization and cleavage.

Friction stir processing was applied to cool-rolled DC04 IF steel plates with a thickness of 3 mm,and the microstructure and mechanical properties of the processed zone were investigated. A defect-free specimen with a shiny and smooth surface is fabricated at a tool rotation rate of 950 r·min-1 and a travel speed of 60 mm·min-1 using additional forced cooling technology after processing.A fine equiaxed grain structure can be obtained in the processed zone,which causes a higher hardness of HV 135.6,1.4 times as large as the base metal at the center of the processed zone,and the highest hardness of HV 312.8 in the surface. The ultimate tensile strength of processed samples with and without the surface fine-grained layer increases by 50.9% and 47.6% compared to that of the base material,respectively. The both fracture surfaces of samples before and after friction stir processing exhibit dimple ductile fracture characterization. Grain refinement is considered to be the main reason for improving the ultimate tensile strength.

Hot compression deformation experiment of pure nickel N6 was conducted on a Gleeble-3800 thermomechanical simulator at a deformation temperature range of 800 to 1100℃, a deformation rate range of 5 to 40 s-1 and at a deformation of 70%. The hot deformation behavior of this material was analyzed at high temperature and high deformation rate. The microstructural evolution and the flow stress curves were obtained at different deformation parameters. The processing maps were drawn by using the dynamic material model. Through analyzing the microstructures and the processing maps, two reasonable regions are introduced for processing pure nickel N6:the deformation temperature range of 1000 to 1100℃ and the deformation rate range of 5 to 7 s-1 or 20 to 40 s-1; the deformation temperature range of 800 to 900℃ and the deformation rate range of 5 to 10 s-1. In these two regions, the microstructure of pure nickel N6 is uniform, while in the region of rheological instability the microstructure is disordered and the grain size is varied. The grain size of pure nickel N6 after hot deformation goes up as the deformation temperature rises or the deformation rate declines.