The polytetrafluoroethylene (PTFE), which was implanted with Ni ion to different energy and doses, fabricated metallic structures by selective electroless copper plating. The characteristic and microstructure of the copper film were studied using SEM and X-ray diffraction. Friction performance of the interface between copper film and basal body of PTFE was tested with a CETR UMT-2 (CETR Co., Campbell, CA, USA) multifunction micromechanics instrument. The test loads were 10, 20 and 40 N, while the line velocity was 8 mm s 21 , and the frequency of data acquisition was 1 Hz. The Ni ion implantation replaces the complicated electroless plating surface pretreatment, and it is an assisted technique of electroless plating of copper on the surface of PTFE and plate Cu directly on its surface. Continuous, prepressing and uniformity plating was obtained with proper technique parameters and the dosage of Ni z . The frictional performance comprehensive property of copper film was remarkably influenced by different plating methods, annealing treatment and testing loads under unlubricated condition. The friction coefficients and wear rates changed with the varied load. Annealing treatment improves the tightness and uniformity of the copper film, while it decreases its cavity. Friction performance of copper film was thus increased. The mechanisms of friction and wear of copper film under different test conditions are also discussed.
Analysis the electricmotorcar aluminum wheels’ hole defect on macroscopic and microscopic, observed that the main defects、concentrated site and the main alloy phase. Combined with the local casting technological parameters, the filling and solidification process of aluminium alloy hub was simulated by using Anycasting software. The results showed that: castings filling smoothly, at the junction of the spoke and the rim and the hub central are easy to produce casting defects. Using the optimized process parameters that is lower pouring temperature, higher pouring height and set the vent to experiment, after comparing the results with the original process known, Shrinkage and porosity defects decreased, but there are still some degree of defects, indicating optimized process parameters have some effect.
Titanium alloy castings are made by means of induction melting technology. The relationships thickness of lamellar α+β phase and tensile strength, yield strength, elongation percentage, and Vickers-hardness, as well as the effect of tensile property on the Vickers-hardness are investigated for Ti-6Al-4V alloy castings. The results show that the relationships between thickness of lamellar α+β phase, and tensile strength, yield strength, specific elongation, and Vickers-hardness meet the Hall-Petch equation. And the tensile property increases linearly with Vickers-hardness.
Using the method of numerical simulation and the AnyCasting software, the simulation for SDAS of Al-Mg alloy wheels for low pressure casting is studied. The simulation model is established and the effects of preheating temperature, melt pouring temperature and cooling water pipes on SDAS in the low pressure casting process was founded. The results show that, SDAS presents linear variation with the increase of preheating temperature and pouring temperature; opened cooling pipes make SDAS smaller. The practice of simulating casting is verified by experiments, and test results and simulation results were consistent.
Based on the interfacial reaction model between Ti and ZrO2 in gravity field, taking account of the effect of electromagnetic field, a comprehensive numerical model for simulation of heat and mass transfer is established to study the interfacial reaction between liquid Ti and ZrO2 in electromagnetic field. With the proposed model, numerical simulations are preformed to investigate the influences of pouring temperature, holding time on the oxygen concentration and reactive layer thickness in metal. The results show that both the oxygen concentration and the thickness of reactive layer in metal increase with increasing the holding time and the pouring temperature. The thickness of reactive layer in electromagnetic field is greater than that in gravity field.
In this work, the effects of centrifugal radius and mould rotation speed on the tensile strength, yield strength, specific elongation, and microhardness on Al-Cu alloy castings are investigated. The results show that, with increasing the centrifugal radius or mould rotation speed, the mechanical properties increase gradually. With increasing the centrifugal radius, the variation amplitude of mechanical properties of Al-Cu alloys at mould rotation speed 600rpm is greater than that at 300rpm. This is due to the finer microstructure and the strengthened grain boundary and then resulting in the increase of the resistance to dislocation slipping.
Al-Cu alloy castings are obtained in the vertical centrifugal field. The effects of solution treatment on the microstructures and mechanical properties of Al-Cu alloy casting were studied by OM, micro hardness tester and room temperature tension and compression test. The results show that, the strength, micro hardness and elongation percentage of Al-Cu alloy casting increase firstly and then decrease as the solution temperature increases, and the mechanical properties reach the maximum values as the solution temperature increases to 530°C. As solution time increasing, the mechanical properties of Al-Cu alloy casting increase firstly and then decrease. When the solution time is up to 6 hours, the mechanical properties reach maximum value.
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