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AZ91 reinforced with four different concentrations (0,0.3,0.6,1)wt% of WS 2 micro particles were fabricated using stir casting method. The samples were deformed by equal channel angular pressing (ECAP) after homogenization. The scanning electron microscopy and X-ray diffraction were used to investigate the microstructure and phase composition respectively. The results reveal that rod-like precipitates produced during the homogenization process are refined and bounded in the grain boundaries by the combined effect of WS 2 enrichment and increasing number of passes of ECAP. The needle precipitates are eminent in 1pass 0.3 wt%WS 2 /AZ91. The β-Mg 17 Al 12 and extracted Al particles are dissolved and secondary phases are produced by dynamic recrystallization after 2pass 1 wt%WS 2 /AZ91. The maximum crystallite size and microstrain distribution have been observed for 1pass 0.6 wt%WS 2 /AZ91. The mechanical properties investigation represents that 2pass 0.6 wt%WS 2 /AZ91 has optimal yield strength and ultimate tensile strength. The (22.143)%, (44.735)% and (92) % increment in yield strength, ultimate tensile strength and elongation have been observed in 2pass 1 wt%WS 2 /AZ91 compared with homogenized monolithic AZ91 alloy respectively. The maximum young's modulus (6696.218MPa) has been found for 1pass homogenized WS2/AZ91 and minimum (4108.165MPa) for homogenized 0.6 wt%WS 2 /AZ91. The ECAP deformed 1pass 0.3 wt%WS 2 /AZ91 exhibits the maximum strain hardening rate. The YTS, UTS, and elongation are (30.41) %, (47.6) % and (51.9)% increased after 2pass-0.6 wt%WS 2 /AZ91. [ABSTRACT FROM AUTHOR]

High-performance as-extruded and peak-aged Mg-9.2Gd-3.3Y-1.2Zn-0.9Mn (wt%) alloys have been fabricated by semi-continuous casting, heat-treating, extruding and ageing processes. The effects of different heat treatments on the microstructure and mechanical properties have been investigated. Lamellar and bulk-shaped 14H-type long-period stacking ordered (LPSO) phase and few RE-rich (RE: rare earth element) particles form by different heat treatments. After hot extrusion, the heat-treated alloy with bulk-shaped LPSO phase exhibits an equal-axial microstructure, while the heat-treated alloy with lamellar LPSO phase across the grains shows bimodal grain microstructure consisting of fine equal-axial grains and coarse deformed grains. The more profuse lamellar LPSO phase in heat-treated alloy generates higher volume fraction of deformed grains and finer equal-axial grains, hence leads to higher strength but lower ductility. After ageing, the alloy with profuse LPSO and β′ phases achieves the superior mechanical properties with ultimate tensile strength (UTS) of 525 MPa, tensile yield strength (TYS) of 420 MPa and elongation to failure (EL) of 6.3%. The alloy strengthening is mainly attributed to the bimodal grain microstructure, LPSO phase, Mg 5 Gd (β) phase and β′ phase. [ABSTRACT FROM AUTHOR]

The Mg-8Gd-4Y–1Zn–Mn (wt%) alloys prepared by semi-continuous casting and homogenizing treatment were extruded using different extrusion ratios and subsequent cooling processes. The microstructure, texture and mechanical properties of extruded alloys were investigated. The dynamic recrystallization process is promoted by increasing the extrusion ratio, while the static recrystallization process is suppressed by subsequent water cooling rather than air cooling. When the recrystallization ratio is relatively low, the non-recrystallized region showing a fiber < 10 1 ‾ 0 > Mg //extrusion direction (ED) texture component dominates the texture characteristic. With the increase of the recrystallization ratio, the recrystallized region exhibiting an abnormal <0001> Mg //ED texture gradually dominates the texture characteristic. The grain boundary energy anisotropy and the grain boundary mobility anisotropy are assumed to be changed by the Gd and Y addition, which affect the preferential growth of the abnormal <0001> Mg //ED oriented grains and eventually lead to the formation of abnormal texture component. The as-aged alloy extruded at the extrusion ratio of 6 followed by air cooling shows the highest strength. The extruded alloys with an intensive abnormal texture component exhibit the best mechanical isotropy in both as-extruded and as-aged conditions. The differences in strength along different directions are mainly resulted from the fiber strengthening. [ABSTRACT FROM AUTHOR]

The ageing behavior of as-extruded Mg-1.5Gd-1.3Y-0.6Zn-0.6Mn (at%) alloy was investigated. The strength and ductility are simultaneously improved during ageing at the peak hardness platform. The alloy aged for 100 h exhibits ultrahigh ultimate tensile strength (UTS) of 538 MPa and good elongation to failure (EL) of 13.1%. [ABSTRACT FROM AUTHOR]