Advanced Materials Research Vol. 852

Abstract: The structural and elastic properties of B2 ScAl doped with Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag and Cd elements are studied by using first-principles calculations. The calculated elastic coefficients of pure ScAl are consistent with other theoretical results. The results of elastic constants indicate that all the ScAl-based alloys discussed are mechanically stable. The bulk modulus B, shear modulus G, Youngs modulus Y, Pugh ratio B/G and Cauchy pressure (C₁₂-C₄₄) are investigated. It is found that the addition of Ru that prefers Al site in ScAl can increase the stiffness of ScAl and improve its ductility.

Abstract: A technic, named as mechanical-electrolysis polishing (MEP), is investigated for space-curve meshing-wheel (SCMW) made of titanium alloy by the selective laser melting rapid prototyping process (SLM), to improve their surface quality. Firstly, the effect of polishing time, voltage, gap between the cathode and the workpiece on the surface roughness and transmission accuracy are analyzed. Secondly, the post-treatment experiment results under different parameters are analyzed, and optimal parameters are obtained by the kinematics experiments. The results show that, the transmission accuracy would be raised with an average of about 1.8% by improving surface quality of titanium alloy SCMW.

Abstract: The influence of the eutectoid structure of hypoeutectic Fe-C alloys by applying electric current pulse (ECP) is carried out. The experiment results show that ECP treatment can produce Joule heating. Joule heating increases the diffusion capability of atoms and the driving force of austenite growth, which promotes austenite crystal growth and accelerate cementite dissolution. In view of the influence of the electron-wind-force made by ECP, it can increase the quantity of moving dislocation. The dislocation pile-up which made by the dislocation motion lead to cementite dissolution. Cementite dissolution can lead to concentration fluctuation in Austenite. ECP can also make the phase transformation barrier and the phase transition drive force of graphite formation decrease. As the result, these phenomena can make cryogenic ledeburite become less and graphite increase. Furthermore, it can also increase the nucleation rate and growth rate of ferrite, which can make the relative amount of ferrite increase and the relative amount of pearlite decrease. Based on our experiments, the effect becomes more obvious with the pulse width increase.

Abstract: In this paper, the Al 7003 alloy in the as-annealed condition was processed by dual equal channel lateral extrusion (DECLE) at room temperature. The microstructure and mechanical properties of the as-annealed and DECLEed alloys were examined. The results showed that the microstructure of as-annealed Al 7003 alloys was refined by the formation of deformation bands, with dislocation cells and subgrains inside these bands. The final grains with an average size of about 250nm are observed. Due to DECLE, tensile yield strength and ultimate tensile strength increase by 84.5%, 35.4%, respectively. Meanwhile, elongation to failure decreases by 40.4%. The fracture was characterized by ductile fracture due to existence of a large number of dimples.

Abstract: FeNiCr alloy with various amount of La₂O₃ powders were thermal sprayed onto 1045 carbon steel substrate. Properties of sprayed coatings were studied by an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. Electron probe microscopy analysis (EPMA), X-ray photoelectron spectroscopy (XPS), were employed to this study. The results show that La₂O₃ can refine the microstructure effectively, and make the element distribution uniform, which leads to the improvement on the properties of the coatings. Meanwhile, the wear rate of the FeNiCr alloy with 1.5% La₂O₃ is smaller than other coatings. Interestingly the rare earth can reduce the friction coefficient, and act as self-lubricant in the oxide debris layer formed on the worn surface in friction. Wear mechanism of the coatings is oxidation wear and a large amount of counterpart material is transferred to the coatings.

Abstract: The effects of solution treatment on the grain size and microstructures of an Mg-4Y-3Nd-3Nd-0.5Zr alloy were investigated. Grain size increased slowly when treated at 500 oC and 525 oC, showing that the hindering effect of eutectic phase on grain growth can be ignored. The fitting relationship equations for average grain size vs. solution time h are =49.92t^0.15 and =45.44t^0.15, respectively. When the solution temperature was increased to 550 oC, the fine dispersion phases was dissolved gradually, leading to a rapidly increase in grain size. The fitting relationship equations for vs. h is=39.69t⁰⁴⁹. The grain growth exponent n at 550 oC is far higher than those at 500 oC and 525 oC.

Abstract: This study aims to identify suitable activators for pack aluminising electroplated Ni in order to provide processing flexibility for forming Ni-aluminide/Ni hybrid coatings on creep resistant ferritic steels at temperatures below 700 °C. Experiments are made using NH₄Cl, AlCl₃ (anhydrous), NaCl and NH₄F activated packs prepared from Al and Al₂O₃ powders. Both NH₄Cl and AlCl₃ (anhydrous) are found to be suitable activators. NaCl may be used as an activator if the amount of Al added is sufficiently high. But, the fluoride salts cannot be used as activators in the low temperature range concerned here due to their strong tendency to deposit AlF₃.

Abstract: In order to meet the need of production and promote the smelting efficiency of converter, Pangang Vanadium-extracting&Steel Making Plant optimized oxygen lance nozzle according to the situation of primary 120t converter semi-steel making and have inspected new oxygen lances smelting effect in industrial test. The test shows that the average oxygen blowing intensity raised 0.19m³/t·min with optimized nozzle, shortened oxygen blowing time by 56s,total iron in final slag reduced 0.7%, dephosphorizing rate rose to 82.10% from 79.06%, which developed a good result.

Abstract: In order to solve the problems of seam tracking for automation welding of large welding structure, this paper has respectively built mathematic model for length of magnetic-control arc according to two typical forms of weld pass in multi-pass welding for V-groove seam. By using Matlab/Simulink to analyze the transformation discipline of welding currents, a method for deviation acquisition based on magnetic-control arc sensing for multi-pass welding is proposed. Welding experiments demonstrates that the method proposed can effectively resolve the dilemma of deviation acquisition during multi-pass welding for thick plates with V-groove seam.

Abstract: The stagger spinning process of 1Cr18Ni9 tube was investigated by using finite element method. The metal flow rule around the roller during the tube stagger spinning was analyzed. The influences of wall thickness of the billet on effective stress and spinning force were studied using software Deform. The simulated results indicate that the proper wall thickness of the billet should be 8~15 mm, for the billet with length of 100mm and inner diameter of 200mm.