Microstructure and corrosion behaviour of arc sprayed Zn–Al–Mg–RE cathodic protection coatings on steel substrates

Abstract

Cored wires and high velocity arc spraying technologies have been used to produce Zn–Al–Mg and Zn–Al–Mg–RE (where RE is rare earth) coatings on A3 steel. The durability of coatings in terms of corrosion resistance is the focus of this paper. To study the effect of RE, Zn–Al–Mg coatings also have been produced as a comparison. The microstructures of original coatings and corroded coatings have been investigated after corrosion tests by SEM and XRD. The potentiodynamic polarisation and electrochemical impedance spectroscopy techniques were carried out to determine the corrosion behaviour of the two coatings in 5% NaCl solution. Metallographic as well as electrochemical corrosion results illustrate that the coatings possess a self-sealing capacity, and that the corrosion products can refine the microstructure and enhance the corrosion resistance. Compared to the Zn–Al–Mg coating, the Zn–Al–Mg–RE coating presents a more obvious and stable self-sealing process.     

Scalable,continuous variable,cellular automaton model for grain growth during homogenisation of vacuum arc remelted Inconel* 718

Abstract

A scalable, continuous variable, cellular automaton (CA) model for the quantitative simulation of normal grain growth is presented. The CA model is based on a discrete solution of the classical Turnbull rate equation for grain boundary motion on a mesoscopic scale. The domain is discretised using a regular cubic lattice considering the first and second nearest neighbourhoods. CA rules were usedto determine the state of each cellbased on the local driving force. The effects of both the boundary curvature and the misorientation of grains were incorporated. The driving force was used to determine the direction of the movement of each boundary cell, forming the basis of a continuous variable cell transition rule. The use of experimental grain boundary characteristics (e.g. energy and mobility) allows one to make predictions on industrially applicable spatial and temporal scales. The model was applied to quantitatively predict grain growth during the homogenisation heat treatment of vacuum arc remelted Inconel 718.     

Microstructures of super high strength Al–10Zn–2˙5Mg–2˙3Cu–0˙14Zr alloys under electromagnetically stirred direct chill casting

Abstract

In this report solidification and homogenisation structures of a super high strength aluminium Al–Zn–Mg–Cu alloy were discussed. Al–9˙8Zn–2˙5Mg–2˙3Cu–0˙14Zr alloy was produced by low frequency electromagnetic casting. Solidification structure constituents of this alloy cast by low frequency electromagnetic casting was first discussed, in particular, boundary phases formed mostly by eutectic reaction were discussed: MgZn₂ included with Cu is a major eutectic phase in boundaries; T [Mg₃₂(Al,Zn)₄₉] included with Cu and Si, and S (Al₂CuMg) are located with boundaries as eutectics; Al₂Cu is crystallised as eutectic among which a part is found separately as globular; Al₇Cu₂Fe is crystallised as a facet shape. Second microstructure homogenised for 10 h at 460^u C was discussed. Constituents homogenised were MgZn₂ with Cu and Al₇Cu₂Fe with Zn.     

一起真空开关炸毁的原因分析

介绍了一起ZN28系列真空开关爆炸事故，并从继电保护动作情况和事故现场两方面对事故原因进行了分析。根据分析的结果得出了事故教训，提出了改进建议。在对后期购进的相同型号的开关进行检查时，发现厂家已进行了与本文观点相同的改进，从而证明了分析的正确性。     

柴油机废气涡轮增压器的研制

介绍了ZN310A4、ZN285A型增压器与柴油机匹配的性能和运用可靠性,针对增压器在可靠性方面出现的问题,实施了多种有效的改进措施;介绍了2001年、2002年开发的新产品———最高压比达4 3、适用于16V240ZJB、C、D以及12V280ZJ型柴油机的ZN315A1、ZN315B型增压器与柴油机匹配取得的显著效果和运用情况、;阐述了为适配16V280ZJB型柴油机新研制的ZN350A型增压器的平台试验性能;推出了正在研制中的最高压比达5、采用无水冷涡轮出气壳的ZN340新型增压器。