Ruina Ma

Influences of Si on corrosion of Fe–B alloy in liquid zinc

Abstract Influences of silicon content on the microstructure and corrosion resistance of a Fe–2·5 wt-%B alloy have been investigated by using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. Si can change the microstructure from hypereutectic to eutectic and furthermore, enhance the corrosion resistance of the alloy in molten zinc. The high corrosion resistance of the alloy was mainly attributed to the eutectic phase increase and solubility of Si in α phase enhancement. The corrosion of these alloys in liquid zinc was controlled by the diffusion mechanism. The reaction products are FeZn6·67, Fe5SiB2 and FeSi. The reaction layer further prevents the diffusion of zinc atoms into the base material and delays the reaction between the substrate and the molten zinc efficiently.

Microstructure and properties of an Al–Ti–Cu–Si brazing alloy for SiC–metal joining

An Al–Ti–Cu–Si solid–liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500–600°C was designed for SiC–metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al–8.5Ti–5Cu–10Si alloy is mainly composed of Al–Al2Cu and Al–Si hypoeutectic low-melting-point microstructures (493–586°C) and the high-melting-point intermetallic compound AlTiSi (840°C). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al4C3 phase at the interface is suppressed by the addition of 10wt% Si to the alloy.

Effect of Si addition on the stability of Al-10Ti-5Cu-xSi alloy/SiC interface

Abstract The effect of Si addition on the interfacial stability of Al-10Ti-5Cu-xSi (x = 0, 5, 10, 15) alloy/SiC is investigated. SiC and the Al-10Ti-5Cu-xSi alloys were compacted to obtain a stable interface with 10 wt% Si. Analysis of the processing conditions and the microstructures indicated that an excellent Ti3SiC2 phase had been formed and the deleterious Al4C3 phase had been eliminated successfully by the addition of 10 wt% Si to the Al-10Ti-5Cu alloy. Formation of Ti3SiC2 increased at first and then decreased, while the formation of Al4C3 was gradually inhibited with increasing Si content. Ti3SiC2 possesses good chemical stability, and flexibility. However, Al4C3 degrades within few days, in composites exposed to ambient conditions. The presence of Ti3SiC2 at the interface and the elimination of Al4C3 together ameliorate the bonding of Al-10Ti-5Cu-xSi alloy to SiC, thereby improving the interfacial stability of Al-10Ti-5Cu-xSi/SiC.

Corrosion behaviour of stoichiometric Fe3Si alloy in liquid zinc

Abstract The corrosion behaviour of stoichiometric Fe3Si alloy in a liquid zinc bath for 3 and 62 h at 500°C was examined. The corrosion products at the Fe3Si/liquid zinc interface were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The corrosion process was controlled by the diffusion of iron and zinc atoms. There were scarcely any silicon atoms diffusing at Fe3Si/liquid zinc interface from the matrix to liquid zinc. The phase transition process of the stoichiometric Fe3Si alloy in liquid zinc was Fe3Si, α, α+ FeSi+δ, FeSi+δ, and the main corrosion products were periodic array of FeSi and δ phase.