Advanced Materials Research Vols. 602-604

Abstract: Slicing of silicon, quartz crystal and other hard brittle materials mainly use dissociated abrasive multi-wire saw slicing technology, which exists some shortcomings, such as severe environmental pollution, lower cutting efficiency, etc. So it is bound to be replaced by fixed abrasive diamond wire saw in the future. At present, generally, the manufacturing technology of fixed diamond wire saw includes electroplating method and resin bonded method. Compared with electroplating diamond wire saw, the resin bonded diamond wire saw has obvious advantages, such as simpler production technique, lower cost, higher cutting efficiency, less environmental pollution, etc. In this paper, the polyurethane was chosen as matrix resin of resin bonded, and phenolic resin was chosen as curing agent, the preparation technology of thermosetting resin bonded diamond wire saw, is researched in this paper. Firstly, the effects of various compositions on resin bonded, are researched, then the optimal fomula and the manufacturing technology are determined

Abstract: With the self-designed system of welding thermal cycle test, low alloy steel of Cr-Mo series was welded through proper welding procedure according to the phenomenon of cold crack and local hardening in weld metal, and in-situ detection of thermal cycle for deposit metal was realized. The results show that self-designed system is reliable within the error range, the maximum peak temperature during thermal process was above 1700°C, it is largely improved than reported formerly.

Abstract: Maximum normal stress criterion can be used to determine the cracking angle in the uniform and non-uniform zone. According to this theory, the propagating process of the crack in non-uniform composite material is simulated based on the finite element method. The results show that the crack advances wave-like and basically along the direction perpendicular to the maximum normal stress, which is of great guiding significance for the fracture resistance of such kind of structure.

Abstract: Zirconium-based dissolver vessels containing highly radioactive and concentrated corrosive nitric acid solution needs to be joined to the rest of fuel reprocessing plant made of stainless steel(SS), which demands high integrity and corrosion resistant dissimilar joints. Vacuum brazing joining process was proposed in the present work to join zircaloy-4 and 1Cr18Ni9Ti SS since fusion welding processes produce brittle intermetallic precipitates at the interface which reduce the mechanical strength as well as the corrosion resistance of the joint. It is observed that Ag-Cu eutectic phase structure was formed in the brazing seam, a reaction layer exhibited in the interface between zircaloy-4/Ag-Cu-Ti. The concentration of the dendrites increases with an increase in bonding temperature. The width of the reaction layer increases with the increase of the brazing temperature and holding time.

Abstract: The single track is the basis of the multi-track overlapping and multi-layer molding in the accumulative manufacturing, and its quality determines the quality of the parts after their being manufactured. The single track experiment on Ti-6Al-4V powders has used Matlab software to fit the experimental data so as to establish the mathematical model. As a result, the experiment has revealed the functional relationships among the width, layer thickness, and power/speed of Ti-6Al-4V selective laser melting single track; and its relationships between its width and layer thickness, width and power/speed, with the period T1=0.0753，T2=0.0542 respectively, satisfy the Fourier series.

Abstract: The surface nanocrystallization process by high energy shot peening (HESP) was carried out on the TANDEM MIG welded joints surface of 7A52 aluminum alloy after artificial aging. The microstructure features of welded joints surface layer were systematically characterized by using optical microscopy (OM) ,transmission electron microscopy (TEM) observations and X-ray diffraction (XRD) analysis. Based on the experimental observation, the banded texture of 7A52 aluminum alloy base metal was eliminated after HESP. After 50min of HESP processing, the thickness of deformed layer in the base metal (BM), weld metal zone (WM) and heat affected zone (HAZ) was 50μm, 70μm and 60μm separately. Obtained from the TEM micrographs, the average grain size of surface layer in the base metal, weld metal zone and HAZ was about 20nm, 26nm and 32nm respectively. The size of grain in the weld metal zone and HAZ was larger than the base metal. Moreover, the distribution of nanocrystalline in the weld metal zone and HAZ was uneven compared with the base metal.

Abstract: The erosion situation of the refractories of the deep reduction electric arc furnace have been introduced firstly, including the regions such as furnace wall, tapping hole and slag hole, and analyzing on the causes of the erosion shows that high temperature, chemical erosion of oxides in slag, as well as physical scour are the main causes of the serious erosion to the lining. Based on the practical production conditions three solutions are provided including preventing oxidation of metallized pellets, control the temperature and carrying out hot-spray-mending on the furnace.

Abstract: In order to overcome the over formed intermetallic compound and the grain boundary penetration phenomenon in superalloys brazed joint using BNi-2 filler, the three variable portion of BNi2+BNi-5 composite filler is used to vacuum braze GH2132 superalloy. The results showed that the addition of BNi5 filler can decrease the formation of intermetallic compounds. For composite brazing filler of BNi2+40%BNi5, the brazing seam mainly composes of solid solution phase. The amounts of intermetallic compounds increased with the increase of brazing temperature and brazing clearance. The microhardness of the intermetallic compound is about 380~400 HV which is detrimental to the mechanical properties of the brazing joint.

Abstract: The effect of metal block as the fillet on the stress distributed in weld-bonded single lap steel joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that it is beneficial when the joints with a couple of right triangle metal block were adhered to both ends of the over lap. It is advantageous of reducing the peak stress in the adhesive layer near the ends of the lap zone in weld-bonded single lap steel joints so that the stress distribution in overlap zone was improved. The load-bearing capacity of the weld-bonded single lap steel joints may be elevated. There is no evidential difference in the effects between the steel and aluminum block.

Abstract: The effect of the shock temperature and time on the impact toughness of the adhesively bonded steel butt joint under Charpy or Izod impact test is studied using the experimental method. The results obtained show that the impact toughness decreases when the shock temperature increased. When the curing time, temperature as well as the open assembly time was set as constant, the higher the shock temperature is, the lower the impact toughness of the joint. Comparing to the Charpy impact test, the Izod impact test is more sensitive to the shock temperature. When the shock temperature is set at a value not less than 300 C, the impact toughness measured is nearly the same as zero due to decomposition, carbonization and volatilization of the adhesive.