Advanced Materials Research Vols. 634-638

Abstract: Because of the high content of Si, traditional machining can hardly machine micro and small structures. While there is almost no microscopic force in the process of micro-electrical discharge milling (MEDM), so it has great advantages. In the process of MEDM for high silicon aluminum (Si-Al) alloy, the impacts of electrical parameters on processing time, the trend and degree of electrode wear are researched. The Al-50wt%Si alloy made by spray forming (SF) and casting forming (CF) and electrode of copper and tungsten are adopted to do the research. Related processing laws are summarized. A micro-3D structure was made by using appropriate parameters based on the experiment and research.

Abstract: The volume change of ITO target sintering at different temperature of 1673K,1773K,1793K,1823K,1853K and 1873K were investigated by means of molecular dynamics simulation. The experimental results revealed that the rate of reduction in bulk was very fast in prior period of ITO green sintering process, and it was slow in later period. The atomic model of ITO green got the smallest value of 890.918nm3 at the 1853K, and the ITO green can receive the highest densification at this temperature. The simulation results can provide theoretical direction for ITO target normal pressure sintering method.

Abstract: The effect of different contents of Ti on mechanical properties in A356 alloy was researched in this study. The results reveal that the variation is not following the law that the more the content of Ti is, the better the tensile strength and hardness would be in the range of 0% to 7.5% Ti. However, the mechanical properties undergo improving first as the content of Ti is less than 0.3% and then reducing with the addition of Ti. Based on the different contents of Ti, the tensile fracture surfaces are studied to verify the effect of different contents of Ti, It is concluded that the variations of tensile fracture surfaces are in accordance with those of mechanical properties.

Abstract: The cellular automaton (CA) method coupling fundamental metallurgical principles was used to simulate the dynamic recrystallization (DRX) behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy in β processed. Using physically based rules for the simulation of nucleation and growth phenomena of dynamically recrystallized grains. The effects of hot deformation temperature and true strain on the DRX characteristic of the alloy during β processed was studied, and the results compared with experiments. The predictions show very good agreement with the experimental results for the alloy.

Abstract: The band microstructure has an adverse effect on the comprehensive mechanics performance of Cr-Mo steel used for ball screw. This paper dealt with the different annealing processes combined with the forming mechanism of the banded structure. It shows that the annealing with long time can basically eliminate the band microstructure.

Abstract: Aero-engine alloys (also as known as superalloys)are known as difficult-to-machine materials, especially at higher cutting speeds, due to their several inherent properties such as low thermal conductivity and their high reactivity with cutting tool materials. In this paper a finite element analysis (FEA) of machining for Incoloy907 is presented. In particular, the thermodynamical constitutitve equation(T-C-E) in FEA is applied for both workpiece material and tool material. Cutting temperature and cutting force are predicted. The comparison between the predicted and experimental cutting temperature and cutting force are presented and discussed. The results indicated that a good prediction accuracy of both principal cutting temperature and cutting force can be achieved by the method of FEA with thermodynamical constitutitve equation.

Abstract: Aluminum-Silicon based die-casting alloys have been extensively utilized in various industrial applications, but their relatively low electrical and thermal conductivities make them unsuitable as high conductivity parts. In this research, silicon content was restricted to a comparatively low level for higher conductivity and magnesium was added to enhance the castabilities. Al-1Fe-0.5Si-xMg alloys showed significantly higher electrical conductivity than conventional Al-Si based alloys. As the Mg content was increased, the mold filling ability measured using a fluidity serpentine test mold was a little decreased, however the hot cracking susceptibility was observed to be first increased and then decreased. The relationship between solidification characteristics and castabilities of Al-1Fe-0.5Si-xMg alloys was discussed based on the cooling curve analysis and microstructural characterization results.

Abstract: The detailed mechanism of divorced pearlite in bearing steels began to be actively discussed more recently. The survey of divorced pearlite in higher Mn bearing steel was carried out through scanning electronic microscope following isothermal transformation heat treatment. The results show that while divorced transformation taking place in the higher Mn bearing steel just slightly below A1, the cementite could be produced in such way as growing on the base of pre-existing cementite particles in austenite, or emerge either in globular particles or in short rod directly from the austenite. Under isothermal transformation, the carbon atoms in austenite prefer to precipitate on the original boundary of the austenite. The enough small size of the cementite particles remained in the austenite is helpful for getting spheroidal cementite particles structure through divorced eutectoid transformation.

Abstract: According to the compositional design of the calcium deoxidizer and the actual practice of producing HRB335 via converter—in BOF end, the percentages of [C] is 0.032%，the concentration of a[O] is 980ppm, the addition of calcium deoxidizer is 1.36Kg per ton of steel, and the argon oxygen activity is 42.84 ppm. The effect of deoxidization exceed the deoxidizer CaBaAlSi, the effect of deoxidization is fine and the product of deoxidization has no adverse effect on the steel quality. This deoxidization process could not only satisfy the quality requirement of the product, but also significantly reduce the cost. And both the finished product rate of rolled products and the mechanical properties meet the requirements of the national standard.

Abstract: Sub-nano structured steel was obtained by cold rolling and annealing martensite microstructure for a plain carbon steel. The mean grain size is several hundreds nanometer. The steel has very high strength and also good total elongation.