Shi Wei Xu

Equal Channel Angular Pressing of Magnesium Alloy Containing Quasicrystal Phase

ZWK510 (Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr) magnesium alloy containing Mg3YZn6 quasicrystal phase was prepared by conventional permanent mold casting. Part of the cast ingot was subjected to equal channel angular pressing (ECAP) directly; another part of the cast ingot was extruded initially, then ECAP was applied to the extruded alloy. After 4-pass ECAP, the fraction of coarse grains of the as-cast alloy was decreased to about 30%, and the grain size of fine grain was decreased to about 2 μm. Both strength and ductility of the as-cast ZWK510 alloy were significantly improved with increasing ECAP passes, which was resulted from broken and dispersed I-phase, and fine grains formed due to recrystallization. The as-extruded ZWK510 had an initial grain size of about 2 μm and bands of quasicrystal phase parallel to the extrusion direction. After the extruded alloy was subjected to ECAP, the grain size of the extruded alloy was further refined, the grain size was refined to below 0.5 um after 8-pass ECAP; and the quasicrystal phase was further broken and dispersed in the matrix. After ECAP, the elongation to failure of the extruded alloy was improved. However, both yield strength and ultimate tensile strength were decreased, which is considered to be resulted from the texture modification during ECAP.

Microstructure and Tensile Properties of Magnesium Alloy Containing Quasicrystallines Processed by Equal-Channel-Angular-Extrusion

Equal channel angular extrusion (ECAE) was performed on as-cast ZW1101 (Mg-11wt%Zn- 0.9wt%Y) Mg alloy containing quasicrystallines. The grain size of α-Mg was effectively refined, and coarse eutectic quasicrystalline phases were broken and dispersed in the alloy by ECAE. The alloy processed by ECAE exhibited a good combination of high strength and high ductility, which is due to the grain refinement and fine dispersed quasicrystallines in the alloy.

Effect of Equal Channel Angular Extrusion on the Microstructure and Mechanical Properties of Magnesium Alloy Containing Quasicrystallines

Equal channel angular extrusion (ECAE) was applied to an extruded ZW1101 (Mg - 11wt%Zn - 0.9wt%Y) Mg alloy containing quasicrystallines. The as-extruded ZW1101 alloy had an initial grain size of about 12 µm and bands of quasicrystalline phases parallel to the extrusion direction. After the extruded alloy was subjected to ECAE processing, the grain size was refined to about 0.5 µm, and the quasicrystalline phases were further broken and dispersed in the matrix. After the ECAE processing, the micro-hardness and yield strength of the alloy were increased, however, the ultimate tensile strength and the ductility of the alloy were slightly decreased.

Mechanical Properties and Damping Behavior of Magnesium Alloys Processed by Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) was applied to commercial pure magnesium alloy, Mg-1wt%Si alloy and Mg-4.2wt%Zn-0.7wt%Y alloy. With increasing ECAP passes, both tensile strength and ductility of the alloys are increased, which are mainly resulted from the grain refinement. At the same time, for the Mg-Zn-Y alloy with inherent low damping capacity, damping capacity is increased after ECAP passes, however, the damping capacity is still low even after 6-pass ECAP. While for the commercial pure magnesium and Mg-Si alloy with inherent high damping capacity, although the damping capacity is decreased obviously after ECAP, Q-1 is still greater than 0.01. The damping capacity after ECAP processing is mainly influenced by grain size and deformation microstructure. ECAP paves a way for the development of magnesium alloys with high strength and high ductility combined with high damping capacity.

Microstructure and Tensile Properties of a Mg-Zn-Y-Zr Alloy Containing Quasicrystal Phase Processed by Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) was performed on extruded Mg-Zn-Y-Zr (Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr) alloy at 300 oC. After 8 ECAP passes, average grain size of the alloy was reduced to about 1.4 μm, and the quasicrystalline phases were broken and dispersed in the matrix. In addition, nano- quasicrystallines were precipitated from the matrix during ECAP processing. After ECAP, the elongation to failure of the extruded material was significantly improved. Only after 2 ECAP passes, the elongation to failure was 29%, and after 8 ECAP passes, it reached 35%, which was three times larger than that of the as-extruded alloy. However, both yield strength and ultimate tensile strength were decreased with the increasing ECAP passes, which was considered to be resulted from the {0002} basal plane texture modification during ECAP.

Effect of Deformation on the Damping Capacity of Magnesium Alloys

Equal channel angular extrusion (ECAE) was applied to an as-cast AZ91D magnesium alloy. The strain amplitude dependence and temperature dependence of damping capacities of the as-cast and ECAE processed AZ91D alloys were investigated by dynamic mechanical analyzer (DMA). Microstructures of AZ91D alloys after ECAE were observed by optical microscopy (OM). In higher strain region, the damping value of 4-pass ECAE deformed AZ91D alloy was the highest among all the AZ91D alloys under different conditions. The damping peaks of ECAE deformed AZ91D alloys detected during heating from room temperature to 400°C were considered to be related to the migration of grain boundaries and the movement of dislocations during recrystallization.