Papers by Author: Zhen Yi Huang

Abstract: This paper investigates the evolution of the deformation mechanisms in a homogenized Mg-10Gd-2Y-0.5Zr alloy ingot compressed at 300-500 °C and 0.1-20 s^-1. It can be found that the basal slip and mechanical twinning are the major deformation mechanisms in the alloy compressed at 300 and 0.1-20 s^-1. Increasing the testing temperature to 350 °C, basal slip, non-basal slip and mechanical twinning control the plastic deformation of the alloy compressed at 0.1-20 s^-1. When the testing temperatures increase further to 400-500 °C, the mechanical twinning is replaced gradually by the local shear bands which are formed by dynamic recrystallization (DRX) grains (referred as transformation bands). The transformation bands have the trend to form the typical DRX microstructure with increasing the temperatures (might be caused by increasing testing temperatures or strain rates). Besides, the transformation bands can also be found in the sample compressed at 350 °C and 20 s^-1 when the temperature in the deformation alloy is high enough to activate non-basal slip and form DRX grains at local zone.

Abstract: In this paper, an as-extruded Mg-10Gd-2Y-0.5Zr alloy was compressed at 3265 s^-1 and -20 °C using a split Hopkinson pressure bar (SHPB) machine. Details about the initial texture and the lattice parameters of the as-extruded alloy were obtained by pole figures combined by orientation distribution function (ODF) and X-ray diffraction (XRD) Rietveld refinement method, respectively. It can be obtained that the maximum average orientation factor being 0.297 can be obtained at 45^o angled to the extruded direction that is the force axis, resulting in the fracture of the impact compressed sample along a plane orientated at an angle of ~45^o to the compression axis. Analysis of the fracture reveals that the fracture forms near the periphery of one face of the specimen and then penetrates into the bulk material subsequently meet near the other face. Even though the local shear deformation exists in the compressed sample, the fracture of the as-extruded Mg-10Gd-2Y-0.5Zr alloy compressed at 3265 s^-1 and -20 °C is not caused by forming the adiabatic shear band (ASB).

Abstract: This paper investigated the twinning mode in a homogenized Mg-10Gd-2Y-0.5Zr ingot compressed at 300 oC and 1 s-1 using transmission electron microscopy observation and schematic method. Details about the primary twinning mode was studied based on the minimum sear criterion by comparing the values of the four major twinning modes in the magnesium alloys. The results show that the twins are formed first by {10-11} primary twinning being step characteristics, and then the secondary twins are formed later around the step by {10-12}secondary twinning. The results also show that the XRD Rietveld refinement method is an effective means to obtain the lattice parameter and to calculate the twinning shear that has important effect on the primary twinning mode in a h.c.p alloy.