Advanced Materials Research Vols. 189-193

Abstract: The tensile model of foams is built using UG software and the tensile deformation processes of microcellular polypropylene foams with different cell sizes are simulated using finite element method (FEM). The effect of cell size on mechanical property is evaluated based on the microstructure of the foams. The cells with small and uniform size are in a state of plane stress, which improved effectively mechanical property of the foams. Whereas the cells with large and nonuniform size are in a state of plane strain, which leads to low mechanical property. The simulation results coincide well with experimental results.

Abstract: 40Cr steel substrate is coated with TiAlN/TiN films by Multi-arc ion technology. The properties of sliding friction and wear on the surfaces of TiAlN/TiN films and substrate are tested by using the machine of friction and wear. The carrying capacity and tribological properties are investigated. The surface morphology of wear specimens is observed and the elements of wear scar center are analyzed. The results show that the friction coefficient of TiAlN/TiN films is lower than 40Cr under the same conditions. The wear scar of TiAlN/TiN films is lower and the wear loss is fewer than 40Cr. The TiAlN/TiN films can successfully reduce friction and wear resistance.

Abstract: Mo/Al₂O₃ solar energy selective absorbing coating is simulated on computer. Mo/Al₂O₃ metal ceramic mixed-film is deposited on stainless steel sheet using magnetron sputtering. Maxwell-Garnett effective medium theory is applied to analyze the optical constant of Mo/Al₂O₃ granular film. As the wavelength λ changes, the variation regulation of Mo filling factor and the optical constant n, k of metal ceramics granular film at 300 nm~800 nm is theoretically calculated, which is based on Mo/Al₂O₃ bulk materials and optical constant of sputtering film. The coating is simulated successfully with Al2O3 optical parameter found in references. The thickness of each film layer and the proportion between Mo and Al₂O₃ are simulated completely, thus the function of each layer is defined and the optimal thickness of film and Mo/Al₂O₃ proportion are determined. Production technology is improved.

Abstract: Effect of two-step deforming and aging process on the properties and structure of Cu-Cr-Zr-Mg-Si alloy was investigated. The results show under the condition of same cold deformation, two-step deforming and aging processes can improve overall performance of the alloy. The hardness obtained by two-step deforming and aging process is higher 6%-9% than that by single-step deforming and aging. The hardness and conductivity are up to 160HV and 88.1% IACS respectively after 80 % rolling and reaging at 480°C for 30min. The particles precipitate along the dislocation and pin on the dislocation during the reaging. These finer particles distribute more uniformly in the copper matrix and result in the higher strength and electrical conductivity.

Abstract: AISI 420 martensite stainless steel was plasma nitrided with/without shot peening (SP) previously at 350 °C. The FF resistance of researched material was evaluated using a rotating bending fatigue machine and a home-made apparatus. The results indicated that low-temperature nitriding alone and the combined treatment both improved the FF resistance of AISI 420 stainless steel significantly. However, the later did not lead to higher FF resistance than the former. FF cracks tended to initiate at microcrack defects induced by SP.

Abstract: In this paper, the microstructure of nanostructured zirconia (ZrO₂) based coating fabricated by newly developed process, high efficiency supersonic atmospheric plasma spraying (SAPS), is studied. The velocity and surface temperature of in-flight particles during spraying were monitored by on-line system and the microstructure and phase composition of the as-sprayed coating was characterized with SEM, TEM and XRD. Meanwhile, the bonding strength between the top coating and bond coating was measured. The results showed the average in-flight velocity of YSZ particles in SAPS was about 430m/s, which was much higher than that of conventional atmospheric plasma spraying (APS). The as-sprayed coating was composed of well-adhered fine lamellar structures with thickness of 1-4μm. The desirable structure was attributed to higher impact velocity of in-flight particles during SAPS process, resulting in the improvement of flattening degree of molten particles. Meanwhile, the SAPS-YSZ coating exhibited a bimodal distribution with small grains (30-50nm) and large grains (60-110nm), the latter was the main microstructure of the coating. In addition, it was found that the monoclinic zirconia existing in the original powders transformed into tetragonal phase after plasma spraying and the bonding strength of as-sprayed coating was as high as 46±3MPa. The high efficiency supersonic plasma spray, which offers some unique advantages over the conventional plasma spraying process, is expected to be potentially used to deposit a wide variety of nanostructured coatings at lower cost.

Abstract: Magnesium alloys have been attracting much more attentions due to its low density, high specific strength and its lightweight during the past 30 years. In this paper, the deep drawing performance of AZ31B magnisium alloy sheets at elevated temperature was studied by the experimental approach. The results indicated that the formability of the AZ31B sheets at elevated temperatures could be improved significantly. The best external forming parameters can be obtained such as heating temperature of sheet, die-punch clearance, punch fillet radius, etc. Simulating the forming process by using the numerical simulation software, we investigated the stress-strain distribution, thickness distribution and forming limit, etc. The thickness distribution by the numerical simulation agrees well with the experimental results.

Abstract: ZrTiN hard coatings were deposited by multi-arc ion plating on tungsten carbide substrates, using separated Ti and Zr targets in nitrogen and argon atmosphere, combined with ion bombardment of samples surface. The films exhibited a dense and fine grained structure with no columnar growth structure. ZrTiN coatings deposited reveal a (111) preferred crystal orientation. For the coatings, solid solutions were formed. The coatings possessed a higher microhardness value (approx. 2700 Hv_0.05) than their binary counterparts. The increased microhardness was probably due to a solid solution strengthening mechanism while depositing. The thickness of the coatings were between 2.0 and 2.3 μm. The adhesive strength of the coating-substrate system was up to more than 70N.

Abstract: Measurement process has an important impact on the reliability of measurement. The reliability of measurement is weighed by measurement uncertainty. It is very difficult to estimate the uncertainty in the indirect measurements according to the transfer formula given by GUM (Guide to the Expression of Uncertainty in Measurement). Monte Carlo method was proposed to solve the problem of uncertainty estimation and seek suitable measurement process in the indirect measurements. The mathematical relation between the measurand and the direct measures is established firstly. Then Monte Carlo method was adopted to conduct the sampling and synthesis of measurement uncertainty contributors. At last, the measurement method was evaluated and improved according to Procedure for Uncertainty Management, which is given by next generation of GPS (Geometrical Product Specification). Experimental result shows that Monte Carlo Simulation method has a good application foreground in the uncertainty estimation and measurement process design.