Papers by Author: Sheng Zhu

Abstract: In this study, Ti-45Al-7Nb-4V alloy protective coating which base on γ-TiAl phase was deposited on the surface of 5803 aluminum alloy by supersonic particles deposition technology. Researchers observed the micro-structure of the TiAl alloy casting and coating by SEM, and researched the electrochemical characteristics and the galvanic corrosion between TA2 titanium alloy and 5083 aluminum alloy or TiAl alloy casting and coating by electrochemical work station. The results show that,the galvanic corrosion current between 5083 aluminium alloy and TA2 titanium alloy declines from 16.2μA to 0.27μA after TiAl protecting coatings are prepared on the substrates, besides, the corrosion susceptibility drops from E degree to A degree. It also manifests that the 5083 aluminium alloy with Ti-45Al-7Nb-4V coatings can be contacted and utilized with TA2 titanium alloy directly, which tackles the issues of gavanic corrosion prevention between aluminium alloys and titanium alloys.

Abstract: In this study, Gamma TiAl intermetallic alloy protective coating was deposited on the surface of 5803 aluminum alloy by supersonic particles deposition. Researchers observed the surface morphology of the coating by SEM, and researched tribological properties of the substrate material and the coating by CETR friction and wear tester and Talysurf 5P-120 surface morphology tester. The results show that,the bonding mechanism of the Gamma TiAl intermetallic alloy coating and substrate is mechanical interlocking and metallurgical bonding. The abrasion mechanism of Gamma TiAl intermetallic alloy coating is abrasive Wear. The friction coefficients of the coating are all lower than 5083 alumium alloy. The friction volume of coatings reduced 36.7% than 5083 aluminum alloy with the friction loads 50N. TiAl coating has great function to anti-attrition and wearability.

Abstract: Al-Mg welding wires applied extensively in aluminum alloy welding field.5183 ingot and 5356 ingot added Sc, Zr and Er were fabricated by DC casting method and extruded into welding wire, furtherly. Surfacing layer on 7A52 aluminum alloy prepared by using automatic surfacing formation system. Optical microscopy (OM) and 1600-5122VD MICROMET 5104 micro-hardness tester utilized to observe microstructure of 5183 and 5356 ingots, to measure micro-hardness of surfacing layer fabricated by using 5183 and 5356 welding wire with Sc, Zr, Er addition, respectively. The results indicated that, owing to addition of rare earth element, re-crystallization of Al-Mg extruded ingot to generate welding wire was restrained markedly; Microstructure was refined obviously when Sc added; And average size of the grains was about 10μm. Micro-hardness of surfacing layer improved after addition of Sc, Zr, Er element in the ingots.

Abstract: In order to develop new protective materials for magnesium alloy, Al-based alloys with different Si-content were fabricated by copper mold casting. Microstructure, erosion properties of the ingot samples were characterized or tested by using spectrum analysis, optical imcroscope, salt testing machine etc, respectively. The results indicated that the microstructure of Al-1.9Si-1.32Mg-0.40Mn was mostly dendritic crystal. That of Al-13Si consisted of α-Al, flaky eutectic silicon and primary crystal silicon. That of Al-18Si-0.01%P was consistent of a large proporation of primary crystal silicon phase, a part of eutectic silicon phase and a little of α-Al phase. With Si-content increasing, anti-corrosion properties of Al-based alloy gradually improved, which could provide theoretical principle to determine chemical elements of protective materials for magnesium alloy.

Abstract: 7A52 aluminum alloy was welded by using 5356 welding wire added Sc, Zr and Er. Microstructure of the welding joint was observed by using optical microscope (OM). Bending property was tested by bending tester. The results demonstrated that, compared to employ traditional 5356 welding wire, the grains in welding zone (WZ) were much finer; The grains in fused zone (FZ) nucleated and grew from the matrix; The grain size along heat affected zone (HAZ) dercearsed gradually.The welding joint prepared by using 5356 welding wire added single 0.3%Sc possessed maxium face bending strength. The welding joint fabricated by using 5356 welding wire added compond 0.1%Sc+0.2% Er possessed maxium rear bending strength. The fine isometric crystal and isometric dendrite generated at the welding zone when the new type 5356 wire added gingle Sc or compound Sc+Er was employed, which make the welding joint represent excellent bending property, respectively.

Abstract: To develop high wear-resistant protective materials for magnesium alloy, high-silica Al-based alloy modified via P-element was fabricated by DC casting method. Microstructure of ingot samples was observed by using optical microscopy (OM), etc. The results demonstrated that Al-Si-0.01%P alloy with unique microstructure and without defects such as voids and rarefaction might be generated by processing control. Owing to modification by Al-P interalloy, primary crystal silicon phase in hypereutectic Al-Si alloy were refined effectively. Its size in Al-18Si-0.01%P alloy decreased from 50μm to 20μm, and distributed uniquely than that in Al-18Si alloy. Al-P acted as heterogeneous core of primary crystal silicon phase, which was the main mechanism for Al-P interalloy to modify primary crystal silicon in Al-Si alloy.

Abstract: Numerical simulation of sequential collision behavior of multi-particles during dynamic formation of Al-based coating on magnesium alloy by supersonic particles deposition demonstrated that continuous tamping effect from subsequent sprayed particles improved significantly compression ratio of former deposited particle and promote effectively deformation and spread out. Analysis to morphology and microstructure of Al-based coating on magnesium alloy by SEM and TEM elicited that subsequent sprayed particles generated two effects including erosion and compaction to former deposited layer of the coating, induced formation of high density dislocation, grains refinement and re-crystallization, which played work-hardening strengthening effect and fine crystal strengthening effect to Al-Si coating.

Abstract: A model experiment about the hydraulic roughness of natural turf used in riverbank was carried out in flume. To examine the rationality of experimental design, the hydraulic roughness coefficient of plexiglass-flume was tested firstly. The result was 0.0085, which is quite normal. Then the tested hydraulic roughness caused by vegetation ranges from 0.020 to 0.090 for the chosen plants, which is also acceptable. Furthermore, the tested incipient velocities of krasnozem, and paddysoil had the range of 0.55~0.65m·s^-1 and 1.0~1.1m·s^-1, respectively. All these experimental results are in normal range, which means that the design of this experimental is rational. Experimental research illustrate that, the roughness coefficient of plant reduces with the increasing of flow velocity. When the mean flow velocity is over 3m·s^-1, Mannings n values vary between 0.025 and 0.035. This phenomenon is accord with the theoretic analysis. During the scouring process, not only the flow velocity, but also the flow duration has an obvious effect on the coarseness of vegetative bed.

Abstract: High entropy alloys emerge as a new type of advanced metallic materials, which have received increasing attentions from material engineers around the world. In addition to high entropy effect based on equiatomic or near-equiatomic and containing five or more principal elements, they exhibit a cocktail effect resulting from interactions among all the elements and the indirect effects of the various elements on the performances. In this study, according to high entropy alloy design principles, corrosion-resistant elements such as Al, Ni, Cr and Mo were used to improve the anticorrosion property, Fe, Co, B and Si as solid solution elements were added to promote the formation of solid solutions with simple structure, and the wear-resisting property increased.

Abstract: Al-based coating on ZM5 magnesium alloy was prepared by Supersonic Particles Deposition (SPD). Electrochemical working station was utilized to test polarization curve, corrosion potential and electrochemical impedance spectroscopy etc. The results indicted that corrosion potential of Al-Si coating was about-767.6mV, much higher than that of ZM5 Mg-substrate; And corrosion current density of the coating sample decreased three order of magnitude than that of the uncoated. Compared to Mg-substrate, the radius of capacitive impedance arc of the coating enlarged and impedance modulus improved two order of magnitude.