Gan Chunlei

Microstructure of Al-4.99Zr-1.1B Master Alloy and Its Grain Refinement Effect on AZ31 Magnesium Alloy

Abstract An Al-4.99Zr-1.1B master alloy was fabricated by in-situ synthesis from Al melt and K2ZrF4+KBF4 mixed powder. The microstructure of the Al-4.99Zr-1.1B master alloy and its grain refinement effect on AZ31 magnesium alloy were studied by XRD, OM, SEM and EDS. Results show that a large number of fine ZrB2 particles can be observed in the Al-4.99Zr-1.1B master alloy. With increasing the addition amount of Al-4.99Zr-1.1B master alloy, the primary α-Mg grains of AZ31 magnesium alloy are further refined and the network structure of the intermetallic β-Mg17Al12 phase is changed into small blocky structure. Upon adding 0.6% Al-4.99Zr-1.1B master alloy, the average size of primary α-Mg grains is reduced from 170 μm to 45 μm. The present results indicate that the ZrB2 particles can act as the effective heterogeneous nuclei of α-Mg grains and is responsible for the grain refinement of AZ31 magnesium alloy.

Microstructure evolution and mechanical properties of biomedical Mg-Zn-Gd alloy wires

In order to manufacture the Mg-Zn-Gd alloy fine wires for the development of new biomedical Mg alloy implant devices, a hot extrusion and cold drawing process which is used to develop the Mg-Zn-Gd alloy fine wires were investigated. The results demonstrate that the Mg-Zn-Gd alloy has good formability. The microstructure and properties of the Mg-Zn-Gd alloy wires were studied by the observations of optical microscopy and scanning electron microscopy. The results show that the process is successfully developed to manufacture the high-quality wires with 3.00 mm diameter. The achievement of the high-quality Mg-Zn-Gd alloy wires is ascribed to the refined microstructure due to dynamic recrystallization during hot extrusion. Additionally, the grain morphology can play an important role in affecting the subsequent cold drawing performance.