Advanced Materials Research Vols. 189-193

Abstract: The requirement of constructing the three-dimensional entity model for oral cavity teeth has been put forward to the research of the orthodontics based on rapid prototyping technology. This paper compares the merits and demerits of the CT scanning and the structured light scanning and finds a method of acquiring the digital model of oral cavity teeth based on the point cloud. Adopt the structured light scanning technology and 3DSS software to acquire the files of the point cloud data, and introduce the files into GeoMagic software. After processing the data files we obtain the high-quality digital model of oral cavity teeth. The optimal scheme and the processing procedure of the point cloud data in GeoMagic software are described in detail in the paper. In addition, we compare the final solid model and the point cloud data and analyses the errors.

Abstract: The regulation of ceramic coating formed by micro-arc oxidation on Mg-3Nd-0.2Zn-0.4Zr(wt%) magnesium alloys has been investigated by SEM and XRD. The relation of phase structure and corrosion resistance of MgO coating formed by micro-arc oxidation in different growth stages has been analyzed. The results have shown that in the initial stages of micro-arc oxidation, the growth of coating accords with linear regularity, which is the stage of anodic oxidation controlled by electrochemical polarization. With elongated treated time and increased thickness of the coating, the growth of coating accords with parabolic and linear regularity, which is the stage of micro-arc oxidation. In the stage of local arc light, the slope of parabola and thickness of loose coating increases so that the growth rate enhances. The phase structure of loose coating is mainly composed of MgSiO3 and the phase structure of compact ceramic coating is mainly composed of MgO. From the stage of micro-arc oxidation to local arc light, corrosion resistance of coating firstly increase and then decrease. The satisfied corrosion resistance corresponds to the coating time ranging from 7 to15minutes.The addition of rare earth elements in the magnesium alloy reduces the amount of smooth areas on ceramic surface. So the ceramic coating becomes more compact and smooth. The rare earth elements don’t form independent phases in ceramic coating but affect the relative proportion of constitution phases, resulting in the reduction of intermixed magnesium phase and the increase of the MgO and MgSiO₃ phases.

Abstract: The effects of ultrasonic deep rolling (UDR) on the fatigue behavior of pre-corroded 7A52 aluminum alloys were investigated. By means of X-Ray diffraction stress measurements and scanning electron microscopy (SEM), residual stress and fractograph of 7A52 aluminum alloys with and without UDR treatment were analyzed. The results indicated that the UDR produced compressive residual stresses with depth approaching 1mm. UDR treatment can extend the fatigue life of the pre-corroded 7A52 specimens to a large extent, depending on the level of corrosion and UDR parameter. For the slightly corrode specimens, the UDR treatment changed the fatigue crack nucleation site from surface to the transition zone between the compressive residual stresses and tensile stresses, resulted in a much longer fatigue life. For the severely corrode specimens, the crack still nucleated by intergranular cracking, however, due to the compressive residual stresses introduced and the closure of the corrosion pits and corrosion micro-crocks, UDR treatment still improved fatigue performance of the pre-corroded 7A52 aluminum alloy substantially.

Abstract: CrN films with deposition rates of 30-190 nm/min were deposited on Si (111) substrates by middle-frequency magnetron sputtering methods. XRD, SEM, EDS and microhardness tests were used to investigate the effects of bias voltages and total gas pressure on the structure and mechanical properties of the resulting CrN films. With the increasing of bias voltages and total gas pressure, the preferential diffraction orientation changed from (111) to (200). A smooth surface was observed by the SEM experiments and the thickness of the film was about 2 µm. The deposition rates and Cr content of resulting films were highly influenced by the magnitude of the bias voltage and total gas pressure. RMS and Ra properties of the CrN films increased when increased total gas pressure or decreased bias voltage. CrN films produced under optimal conditions have an almost 1:1 Cr:N ratio as determined by EDS. The hardness of the CrN film increased from 2200 to 2700 HV when increased the bias voltages from 0 to 200 V.

Abstract: A compact and versatile vibrometer is designed based on self-mixing laser diode vibrometry interference to measure the oscillation amplitude of a piezoceramics (PZT). A fraction of the light emitted by the laser diode (LD) is reflected by the PZT, and then mixes with the light inside the cavity, causing a modulation of the laser output. The self-mixing signal is detected by the photodiode accommodated in the LD package and acquired by a data acquisition and processing system based on sound card and LabVIEW. Amplitude of the PZT is detected by fringe counting. According to results of test, this device can measure the vibration signal with a measurement accuracy of λ/2. The measurable oscillation amplitude range from 0.325 um to 6.5um

Abstract: The influence of saccharin addition on cathodic polarization, cathodic current efficiency, hardness, surface morphology, and internal stress of nickel electrodeposition from a Watts-type plating bath was studied in this work. The results show that the addition of saccharin may enhance the cathodic polarization, modify the surface morphology, increase the hardness, and decrease the tensile stress. In particular, when the concentration of saccharin is 0.4 g/L, the surface of nickel deposition is smoothest. When the concentration of saccharin is 0.05 g/L, the hardness of nickel deposition is highest.

Abstract: In-situ tensile tests with specially designed SEM were conducted to trace the entire process of crack initiation and propagation till fracture in X80 pipeline steel. The mode of crack initiation induced by inclusions under tensile load was investigated. The results show that: (1) All the inclusions crazed and fracture was the typical tensile fracture, which indicates that the inclusions have little effect on the tensile properties of the X80 material under tensile load. (2) When the size of inclusion is larger than the critical size, crack initiated at inclusion/matrix interface first, and could easily propagate into matrix，but the long crack cannot form. When the size of inclusion is smaller than the critical size, cracks first formed in the inside of inclusions but not propagate into matrix. (3) If the area of cross section of round inclusion is less than 100μm², crack initiated firstly in the inside of inclusion. If the area of cross section of round inclusion is larger than 100μm², crack initiated firstly at the inclusion/matrix interface. For the rectangle inclusion, when its area of cross section is below 150μm², cracks usually initiate in the center of inclusions.

Abstract: Through the rolling and performance test, effect of cold-rolled micro-carbon steel rolling parameters and annealing temperature has been obtained on deep-drawing properties. Rolling texture was detected by X-ray diffraction and analyzed by a quantitative of ODF. R-plastic strain ratio was consistent with texture analysis, which provided with a basis for formulating the process parameters of cold-rolled and annealing of micro-carbon steel.

Abstract: The low temperature deposition principle of magnetron sputtering was discussed. Reactive magnetron sputtering technique was used to gain titanium nitride (TiN) thin films on W18Cr4V high-speed steel substrates at low temperature. A series of experiments had been conducted to study the properties of TiN films. The experimental results showed that at the low temperature(<140 °C), magnetic sputtering can be used for the deposition of TiN film with compact, uniform and high nano-hardness, and their tribological properties were excellent, which co-determined by the film structure of low temperature magnetron sputtering and the counter-parts of rubbing pairs.

Abstract: In this paper, the influence of positive and negative voltages to the formation process of ceramic coating on aluminum alloy was studied. The result indicates that, increasing of positive or negative voltage is favorable to the thickness increase and uniformity of the ceramic coating, the thickness of ceramic coating is linear correlation to the positive electrical quantity which is relative to loaded voltages. The ceramic coating is composed of α-Al₂O₃, γ-Al₂O₃ and mullite phases, and the voltages, especially negative voltage can increase the mass fraction of α-Al₂O₃ phase in the outer side of ceramic coating. The effects of voltage parameters on surface morphology of ceramic coating, thickness of ceramic coating and phase composition of ceramic coating is evident, in which the positive voltage is a decisive factor and the negative voltage is an important assistant factor.