Advanced Materials Research Vols. 557-559

Abstract: A study has been conducted on the preparation conditions of Al₂O₃ for the catalysts for diesel particulate matter. The results show that the preparation conditions of Al₂O₃ support had great contribution to performance of Sn-Cu-K-V/Zr0₂-Al₂O₃ catalyst. The conditions of precipitant, pH value and calcination temperature were investigated. The experiment results show that the suitable precipitant was Na₂CO₃, the pH value of the solution was 9 and calcination temperature was 1000°C. The catalyst which active components were loaded on the modified support by immersion method showed better catalytic activity.

Abstract: With the increasing effects of a corrosive environment on aluminum alloys, the corrosion of aluminum alloys has become a severe problem. In this paper, the accelerated corrosion test environment spectrum and corrosion equivalent relationship was systematically studied. The Accelerated Corrosion Test Environment Spectrum of aluminum alloys under a typical marine atmospheric environment was established. The Spectrum is composed of three parts, namely, a periodic infiltration test, a UV irradiation test, and a salt spray test. The Spectrum can well simulate aluminum alloy corrosion in a typical marine atmospheric environment.

Abstract: Effects of melt superheating holding time on microstructure and mechanical properties of AZ31B magnesium alloy were studied. The results show that the grain size of AZ31B magnesium alloy is gradually increased with the elongation of holding time. The grain is the finest without insulation work, and the increase amplitude of grain size is the most when holding for 20 minutes in this experiment. The higher is the melt superheating temperature, the larger the increase amplitude of grain size when holding for 20 minutes is. The tensile strength, yield strength and elongation percentage of AZ31B magnesium alloy specimens are small declined with the elongation of holding time under lower melt temperature. At 850°C or 900°C, the mechanical properties are rapidly declined with the elongation of holding time when holding time is less than 20 minutes, whereas the mechanical properties are slight increased when holding time is more than 20 minutes. DSC analysis shows that the elongation of holding time causes the increase of solidification onset temperature and the augment of solidification range, so the undercooling degree and nucleation rate are decreased in the melt, which result in the grain coarsening and the mechanical properties decrease.

Abstract: The microstructure of as-cast NiAl-33.5Cr-0.5Zr alloy is the eutectic colonies of NiAl and Cr phase with non-continuous Heusler (Ni2AlZr) phase segregating at the cell boundaries. After hot isostatic press (HIP) processing at 1573K, 100MPa for 2h, the Ni2AlZr phase changes into Zr-rich phase. The elevated temperature tensile strength and elongation of the HIP-ed alloy are much higher than those of as-cast alloy. It was noted that this alloy either as-cast or HIP processing exhibits a brittle to ductile transition behavior, which is difference between as-cast and HIP-ed alloy. HIP processing decreases the BDTT of the alloy, especially in high strain rates, and lower the range of BDTT. When the strain rate increases by two orders of magnitude, the BDTT has an approximate increase from150K for as-cast alloy to 100K for HIP-ed alloy. The mechanism responsible for elevated temperature deformation has also been discussed.

Abstract: The electrochemical corrosion behavior of as-cast Mg-7Li alloy in 3.5wt% NaCl aqueous solution was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical workstation. Results showed that the Ecorr and the Icorr of Mg-7Li alloy were -1.5857V and 2.235×10-4A/cm2, respectively. The cathode process was chiefly the hydrogen evolution reaction, and the corrosion rate of Mg-7Li alloy was mainly controlled by anode dissolution. The corrosion products on the alloy surface consisted of Mg(OH)2, Li2O2 and Al(OH)3. The electrochemical impedance spectroscopy (EIS) of Mg-7Li alloy contained two capacitive loops and one inductive loop. The inductance value increased to 250 ohm•cm-2 with a rise in frequency at low frequency region. The value of capacitive reactance decreased with increasing frequency at medium frequency. The capacitive reactance maintained the value of 50 ohm•cm-2 with increasing frequency at high frequency region.

Abstract: Horizontal continuous casting (HCC) Al-18%Si alloy billets were prepared with the addition of fine-grained Al-18%Si as a master alloy. The influence of cooling conditions and this fine-grained structural materials addition on the microstructure and tensile properties were studied. The uniformity of the HCC Al-18%Si alloy billets was also analyzed. The results denote that the HCC Al-18% Si alloy billets showed finer microstructure and better mechanical properties after double cooling. Fine-grained structural material addition can effectively reduce macrosegregation and make both primary and eutectic silicon much finer. The ultimate tensile strength clearly increased with an addition of 15 percent fine-grained structural material compared to the HCC alloy with no addition of fine-grained structural material. However, a small decrease occurred after an addition of fine-grained structural material up to 30 percent.

Abstract: Aimed at the ore characteristics，the flotation flowsheet of one—stage coarse grinding—bulk flotation of copper and molybdenum—regrinding of bulk concentrate—separation of copper and molybdenum was determined effected．Experiment uses the above flowsheet and reasonable conditions to process molybdenum crude ore of molybdenum and copper crude grade being 0.066% and 0.03%,and the better indexes of the molybdenum grade of concentrate is 51.68%,the copper grade of concentrate is 12.60% and molybdenum recovery is 74.33% are got.

Abstract: According to hot compressive test date, relationship between flow stress, temperature, strain rate and strain is studied. Material constant value is researched through single regression, such as activation energy Q, stress level parameters and structure factor A. The results show dynamic recovery is principal in the softening process of .titanium and Ti-6Al-4V-Rare Earth Titanium is positive strain rate sensitive material.

Abstract: After Hydrogen-induced cracking (HIC) test, many hydrogen blisters appeared on the surface of A333Gr6 pipeline steel. The amount of hydrogen blistering depends on the sample location. The amount and area rate of the hydrogen blistering on the surface of A333Gr6 sample near the internal wall are more than those of the sample near the external wall. After the upper part of the hydrogen blisters were torn off, the fracture surfaces of the upper and lower parts of the blister were analyzed by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The cell segregation inclusion of alloying elements which contain Ca and Al sulfides and oxides were observed in most of the nucleation sites of hydrogen blisters. The result shows that the dislocations and the increasing vacancy concentration are the main reasons to form hydrogen cavities in the nucleation sites. The hydrogen pressure which exceeds the strength of the materials will cause the formation of hydrogen blister.

Abstract: The inhibition effect of 2-Mercaptobenzothiazole (2-MB) against the corrosion of carbon steel in sulfuric acid solution was studied by weight loss measurement and electrochemical measurements(potentiodynamic polarization techniques). The results show that 2-MB acts as a good corrosion inhibitor in sulfuric acid solution. Adsorption of 2-MB is found to obey Langmuir isotherm. Polarization curves indicate 2-MB is a mixed-type inhibitor. The effects of temperature and sulfuric acid concentration were also studied.