Advanced Materials Research Vols. 314-316

Abstract: To research effect of welding thermal cycle on the microstructure and mechanical properties of welded joint, two pieces of 60mm thick plates were welded together using automatic submerged-arc welding (SAW) method with suitable welding parameters. After 17 passes welding, the microstructures and phases of the welded joint was carefully observed and analyzed by using a Carl Zeiss optical microscope in different zones of welded joint, and the surface micro-hardness of the welded joint was measured systematically by using microscopic-hardness tester Lycra. Afterwards, the mechanical properties of the weld metals were measured through stretching. Through a series of measurements and observations, the welding experiment results indicate that effect of welding thermal cycle on the microstructure and mechanical properties of welding joint is great, the grains of the bottom of the weld metal are certainty smaller and more uniform, and the bottom of the weld metal have more excellent mechanical properties.

Abstract: This paper describes the experimental system of milling force, the tool geometrical feature and the certain experimental condition in the section of experimental case, which also makes an explanation about the designing of experimental case and the analysis of the experimental data. It also represents the relationship between coefficients associated with the milling process and the milling force applied on the tool in detail. A finite element method is used to make an explicit analysis on the stress and deformation of the milling tool under the application of certain milling force. Finally, a summary is made to conclude the study and its results.

Abstract: To study of the temperature generating mechanism of Titanium Alloy Ti - 6Al - 4V in high speed, and the influence rule of the milling process parameters for milling temperatures, A temperature simulation model of the milling process was found with AdvantEdge, the relationship between the high speed milling parameters and the milling temperature of Titanium Alloy Ti - 6Al - 4V was discussed by the finite element simulation, and the milling process temperature was measured by the half artificially thermocouple methods. The result show that the highest temperature are reached at close to the tool tip in the rack face, the feed per tooth have significant effect on the milling temperature, while cutting depth and milling width have little effect. The milling temperature increase with the feed per tooth increasing，the highest temperature increase with the spindle speed increasing.

Abstract: By the analysis of chemical mechanical polishing flow field about substrate, it is found that the closer to the center of the substrate film, the polishing rate is more uniform; at the edge it isn’t; at the same time near the rotation axis of polishing pad, the polishing rate is little, while far away from the axis the rate is lager. It’s needed to choose appropriate ration on the speed of polish pad and the speed of substrate, in order to obtain a substrate with better flatness. The change on the speed of polishing pad affects polishing rate larger than the change of substrate’s. With PLM-2 precision polishing machine and S8030N slurry, when the rotation speed of polishing pad is 60rom, the substrate’s is 40rpm, sapphire substrate with complete lattice has been obtained. While BOW of substrate is less than 8 microns, TTV of substrate is less than 5 microns, substrate surface roughness is less than 0.5nm.

Abstract: Vacuum diffusion bonding characteristics of GH4169, interface bonding holes and mechanical properties of the joints were investigated. The experimental results without interlayer showed that, with the increasing of diffusion time and diffusion pressure in the range of 950-1150°C and 20-40MPa, the number and size of interface bonding holes decreased and the maximum tensile strength of the diffusion bonding joint was 658 MPa, but the discontinuous interface holes still existed. With the Cu interlayer, interfaces between the solid solution layer and the base metal were prone to intimate contact and the maximum tensile strength of the bonding joint was 745 MPa.

Abstract: ZrB₂-SiC ceramic composites was brazed by using Ti-Zr-Ni-Cu active filler in a vacuum furnace. The microstructure and interfacial phenomena of the joints were analyzed by means of SEM, EDS and XRD. The joining effect was evaluated by shear strength. The results showed that the reaction products of the ZrB2-SiC ceramic composites joint brazed with Ti-Zr-Ni-Cu active filler were TiC, ZrC, Ti5Si3, Zr₂Si, Zr(s,s) and (Ti, Zr)2 (Ni, Cu). The maximum shear strength of the ZrB₂-based ultra-high-temperature ceramic composites brazed joints is 143.5 _{Subscript text}MPa at brazing temperature T=920°C and holding time t=10min.

Abstract: Using the basic model of double edge cutting, the minimum value of the total shear area produced by the two cutting edges is calculated to determine the chip flow direction: shearing takes place in the corresponding direction of chip flow to make the shear area minimum under specific cutting parameters with sharp corner tools. The chip flow angle can be obtained using the expression of the variation of the shear area with the chip flow angle. In this study, RATIO is defined as the ratio of the main to the minor cutting edge length engaged in cutting and is set variable on the basis of the constant equivalent cutting area. The chip flow angle corresponding to different values of RATIO predicted by the current model shows good correlation with the experimental measurement and FEM simulation results for various cutting conditions. An investigation of the effects of RATIO on the chip flow angle has been made under various cutting conditions and it is demonstrated that RATIO has a significant influence on the chip flow angle.

Abstract: By three-point bending experiments on XY-plane of thin-walled super alloy honeycomb sandwich with different types and dimensions of penetrable defects, their failure modes and influence of defects of different types and dimensions on their mechanical properties are researched by observing failure modes and performance curves of test samples. Researches show that when failure occurs on sandwich structures under three-point loading, vertical to XY-plane, buckling depression occurs on center part of the upper plate along with fracture failure occurring on center part of the lower plate. Similar to three-point experiment on conventional structures, failure always occurs in the longitudinal regions near middle loading area. When lateral walls of honeycomb or strengthen points of welding are set at center loading area, fracture failure occurs on the lower plate, or only buckling deformation occurs on honeycomb cores. And by comparison, FE model can be used to evaluate its mechanical performance of thin-walled super alloy honeycomb sandwich with penetrable defects under three-point bending load. It is the experimental basis for improving the structural reliability and damage tolerance of the structure.

Abstract: The failure cause of Φ127mm G105 IEU drill pipe upset was investigated through mechanical properties testing, optical morphologies and fracture surface analysis. The result show that drill pipe upset’s failure reason is the elephant hide and decarburization layer in its out-surface caused by improper upset treatment in forging process. Elephant hide and decarburization layer existing in drill pipe upset changed seriously reduced its strength and fatigue property. Under the effect of alternating stresses, the crack first initiated from the deepest position of elephant hide and developed quickly. In the end, it leaded the drill pipe to early piecing failure.

Abstract: Manual SHS welding is a new method of emergency welding based on SHS reaction. The large amount of Al2O3 created in the reaction restricts the welding performance seriously. In this paper, CaO and MgO were added as slagging elements to improve the characters of the slag, and the effects of their addition have been studied. Results showed that the combustion velocity of the rod decreased when the content of CaO and MgO increased. The rods with 0.2g MgO and 1.2g or 1.5g CaO were easy to control, which combustion velocities were about 12mm•s-1. No obvious changing rule was found for the density of the slag when the content of additives changed. But the densities of slag were all lower than that of metal Fe and Cu. Viscosity calculation showed that the viscosity value of slag increased when the temperature drop. The additive CaO and MgO reduced the slag viscosity. The viscosity value of the slag with 1.5g CaO and 0.2g MgO added was about 0.9 Pa•s at 1450°C and was lower than 0.7 Pa•s at 1500°C. Welding experiments showed the fluidity and the detachability of the slag were improved. Phase composition and microstructure analysis showed that the slag had multi-phases and its matrix was glass. The tensile strength of the joints was above 350MPa, which meets the requirement of mechanical properties for emergency welding. SEM micrograph showed there were slag inclusion in the fracture of welded joint, which was one of the reasons restricting the mechanical performance of the weld joint.