Effect of Mg on the Formation of Periodic Layered Structure during Double Batch Hot Dip Process in Zn-Al Bath

The article presents the results of studies on the influence of Mg on the formation of the periodic layered structure of the Zn-AlMg coatings. These coatings were produced by the double batch hot dip method in a Zn bath and then in a Zn-Al(Mg) bath with a content of 15, 23, 31 wt.% Al and 3, 6 wt.% Mg. The microstructure of the coatings (OM, SEM) was revealed and the phase composition (XRD) obtained in two-component Zn-Al baths and Zn-AlMg baths were determined. The periodic layered structure was found to consist of alternating FeAl3 phase layers and a bath alloy (Zn + Al + Mg). Moreover, it was observed that the addition of 3 wt.% Mg reduces the thickness of the coating in baths containing 23 and 31 wt.% Al. However, the addition of 6 wt.% Mg causes complete disappearance of periodic layered structure in a bath with 23 wt.% Al. In a bath with a content of 31 wt.% Al the addition of 6 wt.% Mg creates a compact layer consisting of the FeAl3 phase containing the precipitation of the MgZn2 phase and Fe2Al5 phase. Such a structure of the coating transition layer limits the growth of the periodic layered structure in the coating.

Forming Mechanism and Bonding Properties of Fe-Si-B Amorphous Strip/Al Foil Laminate Composites by Ultrasonic Addictive Manufacturing (UAM)

Iron-based amorphous foils and metallic aluminum foils are stacked in alternating layer and welding as laminate composites by ultrasound consolidation process with high-frequency acoustic vibrations. It makes the material to play their own advantages as the new focus. In the consolidation process, the most important standard parameters of the mechanical properties of the material are mainly controlled by the normal force, amplitude of the ultrasonic vibration and the travel speed of the sonotrode imposed by the forming. Ultrasonic vibrations, typically 20 kHz, are applied to the foil laterally (along its width) through a sonotrode (welding tool) .In this paper, the optimum parameters of 25μm amplitude, 2.5kN static force and 20mm / s traveling speed are obtained. It is well-known that the microstructure is the most intuitive way to measure the mechanical properties of materials, including hardness and so on. In addition, in this paper, the forming mechanism of Al 1080/ amorphous (Fe-Si-B) and the connection performance of ultrasonic bonding technology are described in detail. scanning electron microscopy (SEM) found that there is a mechanical interface mechanism and metallurgical bonding mechanism. And the recrystallization temperature of aluminum was calculated. The kinetics of interfacial growth at the grain boundary was analyzed. The composition of interfacial material was analyzed by energy dispersive spectroscopy (EDS) in the metallurgical bonding interface of the recrystallized region. It was preliminarily concluded that the Al-rich FeAl3 phase and the AlB2 phase were inferred. In the exfoliation experiment, it was found by X-ray diffractometry (XRD) that the amorphous did not appear to be crystallized. Finally, the laminated materials were tested for mechanical properties.

Corroded Behavior of 310S Stainless Steel in Molten Al-Si Eutectic Alloy

Corroded behavior of 310S stainless steel by molten Al-Si eutectic alloy in high temperature thermal cycles of 495～620°C was investigated. SEM/EDX, XRD and metallographic technique were used for observing and analyzing the morphology, composition and internal microstructure of the corrosion specimens. Results showed: on the surface of 310S stainless steel, after corroded through 300 melting-solidification thermal cycles, a corrosion layer of about 3μm thick, composed mainly of Fe2Al5 phase and FeAl3 phase was formed. Besides, upon observation of internal microstructure of 310S stainless steel after corrosion, plenty intercrystalline precipitation was present, which resulted in relatively severe intercrystalline corrosion. This was considered the principal factor that compromised mechanical property of the specimen of 310S stainless steel.