Applied Mechanics and Materials Vols. 184-185

Abstract: To reduce average particle size，magnesium fluoride was directly synthesized from MgF2 and NH4F，the product was characterized by X-ray diffractomer，scanning electron microscopy. Orthogonal experiment was used to explore the influences of factors on the average particle size. Found that the effect order of factors on the average particle size is MgCl2 concentration，NH4F concentration，reaction temperature，reaction time，in the optimization of process conditions，average particle size is 23.1 nm.

Abstract: 2Cr11Mo1VNbN steel was mainly used in the manufacture of turbine rotor blades, bolts, nuts and other important parts. However, in actual production, the impact value of their products often failed to meet requirements leaving the material scrapping. In this paper, through observation and analysis of the sample microstructure, fracture morphology and the precipitated phase by electron microscopy and energy dispersive spectroscopy, the results showed that: the low impact value of 2Cr11Mo1VNbN steel ring forgings was caused by the abnormal and large grain, uneven tissue and bulky niobium carbide exhalatted from grain boundary which was serious damage to the stability of grain boundary.

Abstract: In this paper, a novel surface reconstruction method is presented to creat a composite surface with point data on surface obtained by CMM. In this method, the 3th non-uniform B-spline algorithm is proposed to reconstruct every single free-form surface on the whole composite surface, and the algorithm for surface blending is proposed to merge every single surface together to achieve the level of G1 continuity. Furthermore, in order to check and visualize the reconstruction model, a special closed-loop RE system is developd by VC++ to constantly guide to measure and reconstruct untill the model fits in with requirements. Examples are included to illustrate the approach.

Abstract: Ther BP neural net model which is a branch of artificial neural net theory was adopted to analyse the problem of aircraft LY12CZ structure corrosion fatigue life considering the effect of stress level and corrosion environment,and Newton interpolation algorithm was used to increase the quantity and enhance the quality of BP net model training data. The application result show that the BP net model can simulate the value and development trend of corrosion fatigue life with higher precision contrast to the traditional method of exponential function fitting.

Abstract: Through the four-point bending test of lath-shaped heat treated AZ31 magnesium alloy, the bending properties and damage characteristics were explored. The results show that the optimal bending strength of the magnesium alloy were 355.1MPa and 259.2MPa for extruded and cast samples, respectively, after corresponding heat treatment with 350°C, 90min and 400°C, 30min. The initial cracks both occurred at the loading point after applied load exceeded the yield limit of AZ31 magnesium alloy. Surface bump, cracks and other damage morphology accompanied by a large number of twinning organizations were found on the surface of the samples.

Abstract: In this paper TiN coating was prepared on stainless steel substrate using arc ion plating technique. The coating samples’ phases, surface morphology, micro-determination chemical composition, loss factor and damping ratio were tested. The phases of TiN coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the TiN coating were analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively. The damping performance of the samples was measured by hammering activation according half power bandwidth method. The loss factor or damping ratio of samples were obtained according frequency response curve. The results showed that damping performance of samples was considerably improved by TiN coatings.

Abstract: The Fe-Se powders have been prepared by hydrothermal method at temperatures of 160, 180 and 200 °C from FeCl3•6H2O and SeO2. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, the major phases of these product powders are all FeSe2, the impurity phase Se can be identified in spite of poor crystallinity of all samples. The poor crystallinity becomes seriously at lower synthesizing temperature under the experimental conditions. These product powders consist of grains, rods or flakes with sizes of 20~300nm, among which the product obtained at 180 °C has the smallest size of 20~40 nm.

Abstract: Amorphous Cr–C alloy coating was prepared by electrodepositing. The microhardness of the coating was tested after annealing from 100°C to 800°C and the crystallization evolution was studied by the analysis of X-ray diffraction (XRD) and differential scanning caborimetry (DSC). The results showed that the crystallization evolution of the coating began at 300°C and finished around 450°C, and intermetallic compound Cr₇C₃ and Cr₂₃C₆ appeared when heat treatment temperature reached around 600°C. The microhardness, corrosion resistance as well as the adhesion of the coating all increased first with the temperature and then dropped until it attained the proper values. The microhardness reached the maximum of 1610HV_0.025 at 600°C. While the corrosion resistance and the adhesion force attained the peak value at about 400°C.

Abstract: This study applies the principle of silane coupling agent (SG-Si900) of alkane chain steric hindrance effect ,using SG-Si900, tetrabutyl titanate and TEOS as the main raw materials synthesizes self-cleaning organic Ti-Si compound materials by hydrolysis, constant temperature polycondensation and distillation. To improve the comprehensive performance, we can adjust the synthesis temperature and some main reaction parameters, such as H2O/Si, SG-Si900/TEOS, Si/Ti. The experiment proves that the best preparation conditions of compound materials is at the synthesis temperature of 80°C, the ratio of H2O/Si is 8, the ratio of Si/Ti is 9, the ratio of SG-Si900/TEOS is 1. The viscosity of the compound materials which were mutually soluble with water at any ratio is 40.9 S and the contact angle of water against composite films based glass which are made by pulling method is less than 5°.

Abstract: Study the horizontal continuous casting mold solidification heat transfer process is not only to optimize the structure of the mold so that it has a uniform stress field, to improve the quality of slab, to extend the mold life basis, and improve production efficiency and cost-effective method. Therefore, oxygen-free copper horizontal continuous casting process as the research object, the establishment of a level of TU1 billet continuous casting mold solidification heat transfer model for the simulation of oxygen-free copper horizontal continuous casting mold solidification and heat transfer process has laid a theoretical foundation.