Advanced Materials Research Vols. 26-28

Abstract: The main factors that influence the deposition efficiency and forming quality are the state of in-flight particles, which are directly effected by process parameter during plasma spray forming. In this study, plasma spraying of ZrO2 powder was employed according to the method of orthogonal experiments, and the relationship between spray parameters and characteristics of in-flight particles, which were monitored by an optical monitoring system of CCD camera, were investigated. Radial basis function (RBF) neural network model had been designed to forecast the temperature and velocity of in-flight particles, and optimized spray parameter. The comparison of the simulations with the experimental results shows the validity of the model.

Abstract: A thermodynamic analysis of the Ti-Zr-H ternary system has been performed by combining first-principles calculations with the CALPHAD approach. To enable the thermodynamic description of the binary systems, the results from our previous evaluation were adopted for the Ti-H, Zr-H, and Ti-Zr systems. The ternary compound, Ti2ZrH4, with an Fd3m-type crystal structure, exists over a wide composition range, and the (Ti)2(Zr)1(H,Va)4-type three-sublattice model was applied to describe its thermodynamic properties. Because of the lack of experimental information available, the enthalpy of formation of the Ti2ZrH4 phase was evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis with some other experimental information. The calculated phase diagrams and the hydrogen isotherms were in good accordance with previous experimental results. Our calculations revealed that the ternary compound decomposes into a bcc and gas phase in the vicinity of 1270 K.

Abstract: The Conical Ring with Inner Steps (CRIS) is a typical profile ring, which is hard to be formed by ring rolling. Less-profile-filling and shrinking-drawing are the two main defects formed in the rolling process. Through the study of the rolling formability of CRIS with different ratio of height to diameter with the combination of FEM simulation method and experimental method, the main factors that affect the CRIS rolling formability are determined. The CRIS forging is designed. And the FEM simulation and experimental results show that the design method is reasonable.

Abstract: Friction stir welding (FSW) process of aluminum alloys was investigated using a two-dimensional Eulerian formulation coupling viscoplastic flow and heat transfer and strain hardening. The thermal equation for the temperature was modified to stabilize temperature distribution using a Petrov-Galerkin method. The evolution equation for strength was calculated using a streamline integration method. Predicted strength was compared with experiments. Based on crystal plasticity, texture evolution was predicted during FSW of AA6061.

Abstract: Grain boundary characteristics are defined by five parameter, grain boundary plane normal and misorientation angle/axis between two adjacent grains. The influence of the grain boundary character distribution on lattice evolution during deformation was investigated using three-dimensional crystal plasticity finite element method (CPFEM). Various combinations of grain boundaries were modeled systematically. In analyzing the numerical microstructural characterization obtained by the simulation, orientation average scheme and correlation parameters between misorientation and its special distribution are used. Inter- and intra-grain structures were investigated using the spatial distribution of lattice orientation. Main emphasis was placed on misorientation distributions around grain boundaries, where grain interaction mainly occurred.

Abstract: Recently the application of lever cam ass’y made of the high-functional polymer is increasing internationally to improve the productivity and weight reduction. But the application of injection molding of lever cam ass’y in our country is not reported yet because of the lack of the optimal selection technique of proper material and the optimal design of injection parameter. In order to solve the problem, the injection molding simulation is used. The modification of gate position and rib thickness was done and the parameters like injection time, injection temperature, packing pressure and cooling time were changed. As a result, the comparison between models was done and the optimal shape of lever cam ass’y was developed.

Abstract: Many engineers want to prevent crack defects because the defect is fatal to casting products and the desire has induced many studies of the crack generation. However, this study is intricate because the casting involves a complicated process; Casting products experience large thermal variations from pouring temperature to room temperature, phase transformation and mechanical contact with mold during the process. Especially, a crack phenomenon like hot tearing involves an interaction between stress and metallurgical properties. In this paper, we studied the relationship between hot tearing and thermal stress considering metallurgical properties. We performed thermal stress analysis as computational method and proposed a hot tearing predictor including thermal and mechanical stress phenomena and metallurgical characteristics. The proposed hot tearing predictor is verified by the results of applying this predictor to different casting conditions.

Abstract: The quality of coatings is directly influenced by the flattening and solidification of many individual molten droplets in plasma spray forming, so many properties such as thermal, electrical, mechanical etc are strongly linked to the real contact between the “piled-up” splats. The research on the transient temperature of impacting droplets and the heat transfer between droplets and substrate plays an important role in improving the quality of coatings. Because of complexity and high cost of temperature measurement systems for molten droplet during flattening in plasma spray forming at present, this paper presents a new kind of simulation measurement system for transient temperature of spray droplets when impacting on substrate based on LabVIEW, which could display the real-time changes of the temperature by waveform graph. Finally, the experiments were carried out on Pb-Sn alloy molten droplets to reveal the close connection between the impacting droplets temperature changes and the coatings quality, and the heat transfer between droplets and substrate was discussed.

Abstract: The recycling of magnesium chloride brines via a multi-step chemical reaction and precipitation process has been studied in waste bittern from a salt purification plant. In this study, the rates of particle (magnesium hydroxide) growth, the effects of initial concentration of reactants and optimum condition of reaction to make high purity magnesium hydroxide were investigated. Produced magnesium hydroxide was separated and washed using carboxy methyl cellulose as sedimentation agent, and used sodium stearate to prevent particle from aggregating. The mean particle size of obtained high quality magnesium hydroxide are 5 μm and concentration is 99.5%.

Abstract: The flow stress-strain curves and other information during hot compression testing of AZ61B magnesium alloy was investigated by simulated test on Gleeble-1500D thermal-mechanical simulator. The relations between Z and other characteristic value, including peak stress, peak strain and grain size, was calculated by regression analysis. The mathematical model of flow stress was introduced to predict the flow stress. The predicting values is close to the experimental values with not more than 10% error.