Advanced Materials Research Vols. 785-786

Abstract: Active thermal NDT is a promising technique for the detection of structural defects in solids. In this paper, the results of the first-stage research devoted to infrared thermographic detection of cracks in titanium alloys are presented. The test results obtained show that the Fourier analysis is a convenient data processing technique in active thermal NDT. Images of phase are more noise-resistant and able to reveal deeper defects compared to images of amplitude. In application to the inspection of bottom-hole defects in 9.6 mm-thick Ti6Al4V titanium alloy samples, it has been found that a minimum detected defect should have diameter from one to two times greater than its depth.

Abstract: Vanadium extration is a significant process to improve the additional value of vanadium-bearing molten iron. This article carried out the experiments of blowing oxygen and smelting on V extration from vanadium-bearing molten iron, which is made from vanadium titanium magnetite by the process of non-blast furnace. The different controlling parameters including the reaction time, temperature and inserting depths of oxygen lance, are studied aiming to increase the rate of V extraction. The thermodynamics calculation is performed during the process. The results show that, the appropriate blowing time is 9 mins, and the end-point temperature of molten pool should be ranged of 1360-1395 °C. Moreover, the larger inserting depth is beneficial to the V extraction. The oxidation patterns of the smelting process are discussed.

Abstract: The oxidation and corrosion behavior of Sn-9Zn-1Bi lead-free solder alloys with different P content were investigated by weighing the mass of the alloy, as well as the effects of P on the microstructure. The results indicate that the oxidation resistance and the corrosion resistance of Sn-9Zn-1Bi solder alloy can be enhanced significantly with the increase of P content. The microstructure observations show that P addition into Sn-9Zn-1Bi solder alloy can refine the microstructure and the numbers of dark rod-like Zn-rich phases are decreased with increasing of P addition.

Abstract: In this paper, effects of different grain refiners on solidification structure of H62 brass under different cooling rates were investigate by macro corrosion, SEM and EDX analyses. Results of experiments indicate that the columnar crystal zone of H62 brass is completely eliminated and the grain size is reduced remarkably by 0.01%B. It has been found that the columnar grain zone is also eliminated by 0.1Ti, 0.1Zr, 0.1Ti+0.1Zr and 0.1Ti+0.1Zr+0.01B additions, respectively, but their grain refining effects are not as good as 0.01B. The grain size of H62 ingot with 0.1Ti addition prepared by sand mold casting is coarser than prepared by permanent mould casting. The microstructures of as cast H62 alloy are composed of α dendrite phases and rodlike β' phases which enrich on grain boundary to form an array structure.

Abstract: In this paper, the torsional fatigue tests under angle control at the constant strain rate of 5×10^-3/s were conducted on 63Sn–37Pb solder over a range of . The relationship of stress and strain for the 63Sn–37Pb solder was investigated. The number of cycle with loading decrease of 25% was thought as the fatigue lifetime. The parameters of Coffin-Manson equation were determined based on the experimental data.

Abstract: The present study describes the effect of trace ZrC additive on the microstructure and properties of Mo-Ti-Zr alloy fabricated by powder metallurgy method. The results indicate that, ZrC addition effectively enhanced the tensile strength of the alloy both at room-temperature and high-temperature, the alloy with 0.4wt% ZrC has the highest tensile strength, which is 611MPa and 513MPa at 25°C and 800°C, respectively. The tensile fracture mainly consists of intergranular rupture at room temperature, while dimple fracture occurred at high temperature, which indicating higher elongation. Through observation from the micrograph and EDS analysis, ZrxOyCz second-phase particles were observed,which is derived from part of ZrC particles reacted with the oxygen and can suppress the oxygen segregation on grain boundary.

Abstract: In this paper, the elastic modulus of a kind of carbide strengthened Mo alloy has been investigated at both room and elevated temperatures. OM image showed that the sintered Mo alloy has an average grain size of ~20 μm. SEM image of the fracture surface of the sintered Mo alloy after tensile deformation to facture showed that intergranular fracture is the dominant mechanism during deformation. A constitutive model has been developed to simulate the elastic modulus of Mo alloys at both room and elevated temperatures. It has been shown that the evolution trend of the elastic modulus predicted by the constitutive model broadly agrees with the experimental counterparts, although most predicted values are slightly higher than the experimental data. The relatively lower experimental data are due to the pores in the Mo alloy, resulted from powder metallurgy fabrication process.

Abstract: P/M Ti-Al-Mo-V-Ta alpha-beta alloys were processed by hot-pressing sintering technique. The effects of Ta additions on microstructure and properties of the Ti-5Al-4Mo-4V alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscope and mechanical properties tests. The results show that minor Ta addition improves the relative density and the mechanical properties of P/M Ti-5Al-4Mo-4V alloys. After sintering for 4h at 1623 K, the relative density and compression strength of Ti-5Al-4Mo-4V-5Ta alloy are 99.3% and 1950 MPa.

Abstract: Aluminum foam was fabricated by using powder compact metallurgy method. The variation of magnesium particle as the metal additive during sintering was investigated. The addition of SiC particles on the morphology of the foams was discussed. The results revealed that for the foamable precursor with magnesium powders (1wt.%) added, the diffusion boundary between magnesium and the matrix could be increased with extending the sintering time. It was thought that the viscosity of melt increased by adding SiC particles so that the coalescence among the pores during foaming was relieved. As a result, the stability of the aluminum foam would be increased during foaming.

Abstract: A comparative evaluation of the corrosion behavior of friction stir welded AZ31 weldments under immersion and electrochemical tests was revealed. Extruded Mg alloy plates of 6 mm thick of AZ31 grade were butt welded using friction stir welding (FSW) process. The specimens were exposed to immersion and polarization environments in order to evaluate their corrosion rates at the corrosive media containing Cl^- with different pH values. This research work proves a better corrosion resistance of AZ31 magnesium alloy welds at the alkaline solution than the acidic and the neutral solutions.