Microstructures and mechanical properties of Mg-Zn-Zr-Dy wrought magnesium alloys

摘要

Microstructures and phase compositions of as-cast and extruded ZK60-xDy (x = 0-5) alloys were analysed by optical microscope, scanning electron microscope, X-ray diffraction and differential scanning calorimetry. Meanwhile, the tensile mechanical property was tested. With increasing Dy content, Mg-Zn-Dy new phase increases gradually, while MgZn_2 phase decreases gradually to disappear. As-cast microstructure is refined gradually; meanwhile extruded one is refined further with decreasing average grain size to 1 μm. for ZK60-4.32Dy alloy. Second phase, tending to distribute along grain boundary by continuous network in as-cast state, breaks and distributes dispersedly in extrusion state. As-cast tensile mechanical property remains almost unchanged at ambient temperature; however, extruded ones are enhanced significantly at ambient and elevated temperatures, respectively. Tensile strength at 298 and 473 K increases gradually from 355 and 120 MPa for ZK60 alloy to 395 and 171 MPa for ZK60-4.32Dy alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.