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The objective of this research is to investigate the effects of equal channel angular pressing (ECAP) plastic deformation processes on the evolution of microstructural distributions and mechanical properties of SiC particles reinforced magnesium metal matrix composites (Mg MMCs). Investigations of the combined effects of the number of ECAP passes and SiC particles weight percentages were considered. The microstructural analysis results demonstrated a uniform distribution of matrix grain sizes and SiC particles (SiCp) segregation along the matrix grain boundaries as the number of ECAP passes increased. As the number of ECAP passes increased the presence and size of secondary phases were reduced at the pure AZ61 magnesium ally and 2 wt% SiCp/AZ61 Mg MMC. In the case of 5 wt% SiCp/AZ61 Mg MMC, the brittle Mg 2 Si secondary phase was observed and detected throughout the whole ECAP processes. The corresponding mechanical properties experimental investigation results confirmed that the elastic modulus was reduced by 47.98% for pure AZ61, increased by 5.38% for 2 wt% SiCp/AZ61 Mg MMC and increased by 25.9% for 5 wt% SiCp/AZ61 Mg MMC. The ECAP deformed 2 wt% SiCp/AZ61 Mg MMC showed the highest performance of strain hardening rate, strength and ductility. [ABSTRACT FROM AUTHOR]

The corrosion behavior and the corrosion films formed on the surfaces of Mg– x Sn ( x = 0.5, 1.0, 1.5, and 2.0 wt.%) alloys in 3.5 wt.% NaCl solution were investigated by immersion tests, electrochemical measurements, corrosion morphology observations, and X-ray diffraction analysis. Immersion tests and electrochemical measurements illustrated that the best corrosion resistance was reported for the Mg–1.5Sn alloy. Both Mg(OH) 2 /SnO 2 corrosion product film and Mg(OH) 2 /MgSnO 3 clusters formed on Mg–1.5Sn alloy surface. Mg(OH) 2 /MgSnO 3 clusters were compact and suppressed the cathodic effect of the impurity inclusions greatly. The Mg– x Sn ( x = 0.5, 1.0, and 2.0 wt.%) alloys only formed loose Mg(OH) 2 /SnO 2 corrosion product film during the corrosion process. [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 microstructure and corrosion behaviors of Mg–15.24Gd–4.75Zn (in wt.%) alloy exposed to 3.5 wt% NaCl solution were investigated under as-cast, solution (T4), and aging-treated (T6 and T6F) conditions. Results show that the LPSO phase is absent in as-cast and T4-treated alloys but present in T6 and T6F alloys. All lamellar LPSO phases are distributed in α-Mg intragrains, which separates the matrix from the eutectic phase. The lamellar LPSO phase can act as a corrosion barrier, and protect the matrix from being easily corroded by decreasing the surface area of the matrix exposed to the NaCl solution at early stages of corrosion. The LPSO phase can also act as an anode during micro-galvanic corrosion with the W-phase, thereby protecting the matrix and restraining the cathodic reaction of hydrogen evolution. The interior of the LPSO phase can further prevent penetration of corrosive ions during subsequent corrosion processes. Thus, samples with the LPSO phase display uniform corrosion morphologies and considerably improved corrosion resistance. [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]