时效工艺对2519铝合金热轧板材抗应力腐蚀敏感性的影响

以腐蚀的强度指标(Kσ)和腐蚀的伸长率指标(Kδ)评定合金的抗应力腐蚀敏感性, 研究了2519铝合金热轧板材在T6、T7和T8状态下的抗应力腐蚀敏感性.试验结果表明,2519铝合金热轧板材的抗应力腐蚀敏感性按T8>T7>T6 排序,而它们的力学性能按T6>T8>T7的顺序排列.另外,测试了室温下T6、T7 和T8状态2519铝合金试样的恒电位极化曲线,发现可以以合金的极化电阻定性地描述合金的抗应力腐蚀敏感性,且当合金的极化电阻越大时,合金的抗应力腐蚀敏感性越好.     

Introduction of carboxylic acid group to polypropylene fabric for battery separator

Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto a polypropylene (PP) nonwoven fabric for a battery separator. The AAc-grafted PP nonwoven fabric was characterized by IR, SEM, and TGA. The wetting speed, electrolyte retention, electrical resistance, and tensile strength were evaluated after grafting of AAc. It was found that the wetting speed, electrolyte retention, thickness, and ion-exchange capacity increased, whereas the electrical resistance decreased with increasing grafting yield. The elongation of AAc-grafted PP nonwoven fabric decreased with increasing grafting yield in dry state, whereas the elongation increased in wetting state.     

Pitting corrosion of rheocast A356 aluminium alloy in 3.5 wt.% NaCl solution

In this study, the microstructure and corrosion behaviour of rheocast and gravity-cast A356 aluminium alloys were examined and compared. Scanning Kelvin probe force microscopy (SKPFM) results proved that large potential differences between iron-containing intermetallics and the α-Al matrix were responsible for the initiation of the attack at the intermetallics/α-Al interfaces. For longer immersion times, corrosion attack proceeded through the eutectic areas. Semisolid processing refined the eutectic silicon and iron-intermetallics and reduced the potential difference between secondary phases and the matrix. This resulted in improved pitting corrosion resistance of the rheocast A356 aluminium alloy.     

Erosion–corrosion of HVOF-sprayed Fe-based amorphous metallic coating under impingement by a sand-containing NaCl solution

Erosion–corrosion (E–C) behaviour of a Fe-based amorphous metallic coating (AMC) compared with 304 stainless steel (304 s.s.) was studied under a slurry impingement condition in a sand-containing NaCl solution. AMC exhibited much higher resistance to E–C than 304 s.s. The weight loss reached the maximum at an impact angle of 90° and the critical flow velocity was about 15 m/s for AMC, while 45° and 9 m/s for 304 s.s. The increment in passive current density under impingement for AMC was about 10 times lower than 304 s.s. Passive films formed at different impact velocities were of different thicknesses.     

In search of functionality for efficient inhibition of mild steel corrosion both in HCl and H2SO4

Abstract

While the organic ammonium compounds are known to be effective against mild steel corrosion in HCl, these cationic salts are not as effective in sulphuric acid media. A new series of tertiary diallylamines containing C₁₂, C₁₄, C₁₆ and C₁₈ alkyl hydrophobes, N-hexadecylpyrrolidine and their corresponding ammonium salts were found to be among a rare class of inhibitors in arresting mild steel corrosion in HCl as well as in H₂SO₄ media effectively. While all the inhibitor molecules exhibited excellent inhibition efficiencies (%IEs) (～99%) in 1M HCl, ammonium salts containing alkyne moiety at 400 ppm provided 93–97%IE even in 7·7M HCl. The inhibitors (400 ppm) containing diallyl moiety demonstrated the %IEs in the range 80–97% in 0·5M H₂SO₄. The interactions of the π electrons in the diallyl moiety with the low lying vacant d-orbitals of iron help the inhibitor molecules to undergo adsorption and interfere with the anodic dissolution process.     

Effect of chloride ions on corrosion behaviour of austenitic nickel and nickel free stainless steels in phosphoric acid solutions

The effect of chloride ions' presence (0·005–1·0M NaCl) in phosphoric acid solutions (5, 40 and 75%) on the corrosion behaviour of three austenitic stainless steels (an experimental steel Fe–18Cr–12Mn–0·6N and two trade grades, Fe–18Cr–9Ni and Fe–14Cr–15Mn–0·2N) has been studied by potentiodynamic polarisation measurements. The surface examinations of the samples tested involved X-ray photoelectron spectroscopy as well as optical and scanning electron microscopy. It was established that chlorides added to phosphoric acid solutions deteriorate the general corrosion resistance, and under anodic polarisation, they provoke pitting corrosion. The composition of the stainless steels significantly influences its corrosion behaviour in the phosphoric acid solutions containing chloride ions. The replacement of nickel with manganese and nitrogen on top of lower chromium content has a strong negative effect on the corrosion resistance.     

Resistance spot welding control based on the temperature measurement

Abstract

In this paper a novel approach for temperature measurement during resistance spot welding is presented. The temperature is measured by two thermocouples mounted at the ends of both the electrode tips. The authors chose to mount them there because it was expected that it would be possible to measure the temperature at this point using a digital camera in the near future. The research was, therefore, motivated to obtain various pieces of information about the welding process from the measured temperature profiles. The measured temperature profiles showed a good correlation with the weld strength. Other phenomena, such as expulsion and electrode wear, can also be related to a temperature profile.     

Analysis of weld defects in similar and dissimilar resistance seam welding of aluminium,zinc and galvanised steel

Abstract

In the present investigation, a microstructural characterisation of welds performed by resistance seam welding was carried out, with special focus on weld defect analysis. In order to perform a comparative weldability analysis, the welds were performed using similar welding procedures. Similar welds in aluminium (5754-H22) and zinc (Zintek) alloys, as well as dissimilar welds between galvanised steel and zinc, were studied. The defective aluminium welds were found to be characterised by important grain growth inside an inhomogeneous nugget and by the presence of important voids and cracks. The zinc welds showed a well defined nugget, but with porosities and some cracks. In the dissimilar steel–zinc welds, important macroscopic defects were observed. Microstructural analysis evidenced the occurrence of melting at the zinc side of the welds; meanwhile, no microstructural modifications could be observed for the steel side. Defect formation, as well as weld morphologies, was related to the variation in welding parameters.     

TiC增强高锰钢基复合材料的组织与磨损性能

高锰钢是传统的耐磨材料。为进一步提升高锰钢的耐磨性能,使其能满足复杂工况的使用要求,本文采用凝固析出方法制备了不同体积分数TiC增强的高锰钢基复合材料,系统研究了复合材料的显微组织和磨料磨损性能。热处理后,复合材料由奥氏体和TiC两相组成,TiC颗粒均匀分布在高锰钢基体中,颗粒与基体界面清洁。磨料磨损实验表明,TiC颗粒的引入提高了复合材料耐磨性能。然而,复合材料的磨损性能随着TiC体积分数的增加而降低。研究表明这是因为随着TiC体积分数的提高,陶瓷粒径尺寸增大且部分形成团簇,陶瓷颗粒在磨损过程中发生破碎从而提高磨损率。     

EIS assessment of critical pitting temperature of 2205 duplex stainless steel in acidified ferric chloride solution

In this study, critical pitting temperature (CPT) of 2205 duplex stainless steel (DSS2205) was assessed using electrochemical impedance spectroscopy (EIS) in ferric chloride solution. In order to verify the results other methods such as ASTM G 48, potentiodynamic and potentiostatic polarisation and zero resistance ammeter (ZRA) were also employed. The results show a strong close relation between the results of this method by those of previous methods. CPT of the alloy is 40 °C based on standard method and 44 °C, 49 °C according to the ZRA and potentiostatic methods. Both potentiodynamic and EIS methods give an almost identical CPT value.