Hui Diao

Compressive behaviour of nanocrystalline Mg–5Al alloys

Abstract Magnesium alloys are attracting increasing research interests due to their low density, high specific strength, good machinability and availability as compared to other structural materials. However, the deformation and failure mechanisms of nanocrystalline (nc) Mg alloys have not been well understood. In this work, the deformation behaviour of nc Mg–5Al alloys was investigated using compression test, with focus on the effects of grain size. The average grain size of the Mg–Al alloy was changed from 13 to 50 nm via mechanical milling. The results showed that grain size had a significant influence on the yield stress and ductility of the Mg alloys, and the materials exhibited increased strain rate sensitivity with a decrease in grain size. The deformation mechanisms were also strongly dependent on the grain sizes.

Bonding of Aluminum Alloy by Hot-Dipping Tin Coating

This paper presents bonding technology of aluminum alloy by hot-dipping tin. The dissolution curve of copper in molten tin liquid was obtained in the experiment of hot-dipping Sn. Optimal hot-dipping parameter which was suitable for soldering was designed. To elucidate characteristics of interfacial evolution, the microstructure of the coatings, soldered joint were analyzed using optical microscopy, SEM and EDX. The shear strength of soldered joints was tested as high as 39.9Mpa, which is high enough to achieve the requirement of electronic industry.

Indentation Size Effect and Strain Rate Sensitivity of Nanocrystalline MG–AL Alloys

Deformation behaviour of microcrystalline and nanocrystalline (nc) Mg-5%Al alloys were investigated using instrumented indentation tests. The hardness values exhibited significant indentation size effect (ISE), with nc alloys showing weaker ISE. Relative higher strain rate sensitivity and inverse Hall–Petch relationship were observed in the nc alloys. This is attributed to highly localized dislocation activities and relative smaller activation volume, as compared to their mc counterparts. It is believed there is an increasing role of grain boundaries in plastic deformation mechanisms with decreasing the grain size.

COMPRESSIVE BEHAVIOUR OF NANOCRYSTALLILNE Mg-5%Al ALLOYS

Magnesium alloys are attracting increasing research interests due to their low density, high specific strength and good mechineability and availability as compared to other structural materials. However, the deformation and failure mechanisms of nanocrystalline Mg alloys have not been well understood. In this work, the deformation behavior of nanocrystalline Mg-5% Al alloys was investigated using compression test, with a focus on the effects of grain size. The average grain size of the Mg-Al alloy was changed from 13 µm to 50 nm via mechanical milling. The results showed that grain size had a significant influence on the yield stress and ductility of the Mg alloys, and the materials exhibited increased strain rate sensitivity with decrease of grain size. The deformation mechanisms were also strongly dependent with the grain sizes.

Deformation behaviour of nanocrystalline Mg-Al alloys during nanoindentation

The deformation behaviour of Mg-5%Al alloys and its dependence with gain size and strain rate were investigated using nanoindentation. The grain sizes were successfully reduced below 100 nm via mechanical alloying method. It was found that the strain rate sensitivity increased with decreasing grain size. The smaller activation volumes and the plastic deformation mechanisms involving grain boundary activities are considered to contribute to the increase of strain rate sensitivity in the nanocrystalline alloys.