Advanced Materials Research Vols. 311-313

Abstract: Using finite element method, a quenching analysis of 7075 aluminum alloy thick plate is carried out. The effect of surface heat transfer coefficient and plate thickness on residual stress, and the effect of cladding material on residual stress are discussed. It shows that the bigger surface heat transfer coefficient or thickness is, the bigger the residual stress is, and the residual stress significantly reduces while the cladding material exists. Experiments validated the simulation results.

Abstract: The semisolid slurry of A356 Al alloy was preparation by low superheat pouring and weak traveling-wave electromagnetic stirring. The effects of pouring temperature and stirring power on the semisolid slurry were researched. The results show that the shape of primary α-Al experiences a transition from rosette-like grains to spherical grains with the pouring temperature lowing gradually, and the smaller grains with a spherical appearance distribute in the microstructure homogeneously. The appropriately raising the electromagnetic stirring power is good for the formation of the semisolid A356 Al alloy slurry with spherical microstructure. On the condition of weak traveling-wave electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring. Therefore the pouring operation is simple and convenient.

Abstract: Two kinds of ZL108 alloys containing titanium are produced with electrolytic low-titanium aluminum alloy (named as ZL108D) and pure aluminum as well as Al-Ti master alloy (named as ZL108R) respectively. The influence of different titanium alloying methods on the microstructure and wear behavior is investigated. The result shows that it is an effective for grain refining of ZL108 alloy by adding titanium to the melt before casting. Addition of titanium can improve the wear resistance of ZL108 alloy, while ZL108D is superior to ZL108R. It is attributed to the addition with electrolytic low-titanium aluminum alloy results in better grain refinement.

Abstract: Based on the characteristics of the flow stress curves for one new kind of metastable Ti2448 titanium alloy from isothermal hot compression tests, the constitutive model was developed to describe the relation between flow stress and strain, strain rate, deformation temperature completely. During this process, the flow behavior of alloy at high temperature undergo flow softening caused by dynamic recovery (DRV) was modeled by the adopted hyperbolic sine function based on the unified viscoplasticity theory, the further drop in flow stress after the peak value in stress-strain curves was assumed to be caused by temperature rise and the constitutive model was modified accordingly. Additionally, the material constants were determined by optimization strategies, which is a new method to solve the nonlinear constitutive equation. The stress-strain curves predicted by the developed constitutive model well agree with experimental results, which confirms that the developed constitutive model gives an accurate estimate of the flow stress of Ti2448 titanium alloy and can provide an effect method to model the flow behavior of metastable titanium alloy at high temperature.

Abstract: The impact disrepair and adhering disrepair of milling insert are the important factors that affect the normally running of the automated processing system. Based on machining the 45 steel, find out the difference of the impact disrepair invalidation types between the waved-edge milling insert and flat rake milling insert, build the impact disrepair life cumulating distribution function mathematic models by the mathematics statistic method and have contrast analysis of the impact disrepair average lives between them. Based on the experiments on milling the 3Cr-1Mo-1/4Vsteel, find out the difference of the adhering disrepair invalidation types between them, build the quantitative mathematic relation between milling temperature and maximal adhering disrepair depth on rake face, and analyze the rule that the milling temperature affects the adhering disrepair. All these studies provide the theoretic and experimental bases for the groove optimization.

Abstract: Aiming at the problem of the influence of joints on machine structure static performance, this paper presents a method of modeling and experiment on static characteristic of BT tool holder-spindle interface. A FEA model of tool holder-spindle interface is established by setting several equivalent springs, whose parameters are identified through experiment. The effectiveness of the proposed method is tested and verified by building finite element model and applying the spring parameters to it. The comparison between the emulational result and experimental result shows that the simulation accuracy has improved tremendously, which the relative error reduces to less than 10% under different axial forces.

Abstract: The kinetics and products of oxidation of ternary Co-10Cr-5Si alloys in 1 atm of pure O₂ at 700 and 800°C were investigated. The scales were composed of an outer CoO layer and an inner complex layer consisted of cobaltous oxide, Cr₂O₃ and SiO₂. Internal oxidation zones were found beneath the nodules formed at 800 °C. However, there was no internal oxidation zone present beneath the scales formed at 700°C.

Abstract: Chemical compositions of Cadmium and lead were measured with conditions that the temperature between 400-700°C and remaining pressure of 10-60 Pa as in which Materials containing Cadmium and lead evaporate. Activity coefficients of cadmium and lead were calculated using the generalized least squares（GLS）, three relations were deduced in Cd-Pb system，namely relation between activity coefficients and temperatures, relation between activity coefficients and chemical compositions, and that of activity coefficients and temperatures together with chemical compositions. This article provides a theoretical reference data for separation of alloys in cadmium systems.

Abstract: The determination of titanium alloy phase transformation point is very important for phase transformation is the theoretical basis of titanium alloy heat treatment. One new type of titanium alloy Ti-5Al-3.3V-8Mo-10Nb-1.0Zr-0.5Cr was designed and prepared, then the (α + β→β) phase transformation point of this alloy was determined using simulation method, calculation method and continuous heating-up method, and the comparison on these methods has been made in accuracy and simplicity. The phase transformation point was obtained rapidly by simulation method with the value of 806°C, it was obtained by calculation method with the value of 804.28°C, According to the results of software simulation method and calculation method ,the phase transformation point 805 is obtained by the continuous heating-up method. Compared the results of three methods, the results measured by three methods are quite approachable, the phase transformation point was 805±1°C, and the software simulation method is the most accurate and simple.

Abstract: Firstly, realizes module partition and simplification of product level CAD model using modularization and hierarchy design flow. Then, identifies the correlative relations of the same rank subassemblies through their individual main control part; identifies the correlative relations between all parts in one subassembly or between all features in one part through main control parameters of each part. Finally, builds an assembly tree based on all association rules for variant design of conveyor, and confirms the feasibility of this method.