Wang Shuncheng

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, Texture and Mechanical Properties of Extruded Mg-Zn-Zr Mg Alloy Profiles

Abstract The microstructures, texture and mechanical properties of large scale ZK60 magnesium alloy profiles were systematically investigated by XRD diffraction, microstructure observation and tensile testing at room temperature. The results indicate that there are mainly two phases in the extruded ZK60 Mg alloy, i.e. α-Mg and MgZn 2 , while a small amount of Mg 2 Zn 11 and Zn 2 Zr 3 phases were also observed. Initial coarse grains were significantly refined and broken down along the extrusion direction (ED), and partially dynamic recrystallization (DRX) also takes place during the hot extrusion process. The basal plane in most grains is aligned to ED and transverse direction (TD) rather than commonly extruded fiber texture. In the tensile test, the samples of 45ED direction exhibit the highest elongation to failure (δ=28% and 23%), and the ED direction reveal the highest ultimate tensile strength (σ b =325 MPa and 312 MPa) along middle and side parts, respectively.