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In this work, as-cast Mg–Ni–Y alloys were proposed to develop a feasible material for fracturing balls, and their mechanical performance and corrosion behavior were systematically investigated. Long period stacking order (LPSO) phase was firstly introduced to improve both the mechanical properties and degradation rate of magnesium alloys. With the increase of LPSO phase, the compressive strength was improved significantly, while the elongation of the alloys decreased owing to the relatively brittle nature of LPSO phase. Due to the higher corrosion potential of LPSO phase, the LPSO phase can accelerate the corrosion process by providing more micro-couples. However, the LPSO phase would serve as the corrosion barrier between the corrosion medium and the matrix when the contents of LPSO phase are too high in Mg92.5Ni3Y4.5 and Mg87.5Ni5Y7.5 alloys. As-cast Mg97.5Ni1Y1.5 alloy with satisfactory mechanical properties and rapid degradation rate was successfully developed, exhibiting a high degradation rate of 6675 mm/a (93 °C) in 3 wt.% KCl solution and a favorable ultimate compressive strength of 410 MPa. The degradation rate of Mg97.5Ni1Y1.5 alloy is 2–5 times of the current commercial magnesium alloy fracturing materials. [ABSTRACT FROM AUTHOR]

Abstract The high-performance Mg-8.8Gd-3.4Y-1Zn-0.8Mn (wt%) alloy sheets were prepared by large-strain high-efficiency rolling process. The large strains with ~ 87% and ~ 91% total reduction were introduced in the hard-to-deform Mg alloy by hard-plate rolling process at 400 °C for merely 3 and 2 rolling passes. The microstructural morphology and texture were examined, and the tensile tests were performed along rolling direction (RD) and transverse direction (TD). The large-strain rolling process brings in refined grains, homogeneous dispersive LPSO phase and β phase and weakened basal texture. The anisotropy of the strength and elongation is improved after rolling. The as-rolled sample with ~ 91% total reduction exhibits excellent mechanical properties with ultimate tensile strength (UTS) of 434 MPa, tensile yield strength (TYS) of 318 MPa and elongation to failure (EL) of 10.7% parallel to the TD. By quantitating the relation between grain orientations and the deformation modes, it is confirmed that the basal slip and prismatic slip are the dominant deformation modes at the initial stage of plastic deformation, meanwhile the pyramidal slip and extension twinning are the complementary deformation modes. Highlights • The hard-to-deform Mg alloy has been rolled with a large reduction per pass (~ 70%) and a large total reduction (~ 91%). • The as-rolled Mg alloy exhibits an improved anisotropy with high strength and appreciable ductility. • The quantitative relation between grain orientations and the deformation modes has been uncovered. [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 effect of Al content on the microstructure, damping behavior and mechanical properties of Mg-xAl-0.5Ce (wt%) damping alloys was systematically studied. Al content had a great effect on the morphology features of Al 4 Ce phases. The quasi-rectangular network structure was observed in as-cast Mg-1Al-0.5Ce alloy. The Al addition promoted the dynamic recrystallization during extrusion process and led to the texture weakening, but the basal texture was sharpened with further Al addition due to the consumption of the Ce solute. The as-extruded Mg-1Al-0.5Ce alloy showed the best damping capacity among as-extruded Mg-xAl-0.5Ce alloys, which was mainly ascribed to the texture weakening. The ductility was improved with increasing Al content, while the strength was reduced. This behavior was related with the texture weakening and increasing grain sizes. The as-extruded Mg-1Al-0.5Ce alloy exhibited the excellent comprehensive performance. The peak P 2 of as-extruded alloys in the first heating run was a superimposed peak, consisting of a grain boundary relaxation peak and a recrystallization peak. The grain boundary peaks P 2 in the second heating run shifted to lower temperatures and their activation energies decreased with increasing Al content. The reasons for the variation of the grain boundary peak P 2 were discussed. [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]