Search

Compared with the sole Ca or Ce/La element, the Ca-Ce/La synergistic microalloying represents an excellent strengthening effect in extruded Mg–Zn alloy, which is mainly attributed to the grain refinement during the extrusion process. Ca-Ce/La addition results in the refinement of the secondary phases and precipitates, promoting the pinning effect for dynamic recrystallized grain growth and dispersion strengthening effect, which also contributes to the increased yield stress. Furthermore, Ca-Ce/La combined addition leads to the more uniform distributions of fine secondary phases, which can improve the ductility and promote the particle stimulated nucleation effect, resulting in a weak basal texture in extruded Mg–Zn alloy. [ABSTRACT FROM AUTHOR]

Abstract: The effect of long period stacking ordered (LPSO) phase on the microstructure, texture and mechanical properties of extruded Mg–Y–Zn alloys with compositions of Mg98.5Y1Zn0.5, Mg95.5Y3Zn1.5 and Mg92.5Y5Zn2.5 (at%), was systematically investigated. The LPSO phases were aligned along the extrusion direction (ED) in the as-extruded Mg–Y–Zn alloys, and significantly enhanced the dynamic recrystallization (DRX) process during the hot extrusion. With the increase of LPSO phase, the degree of DRX process of Mg alloy was more completed, the growth of the DRXed grains resulted in the grain coarsening, and the following phenomena were also observed that the conventional basal fiber texture was remarkably weakened, a novel texture component of 〈0001〉//ED appeared in the Mg alloys with higher volume fraction of LPSO phase. The microhardness and tensile yield stress (TYS) of Mg–Y–Zn alloy was improved by LPSO phase, but the ductility was degraded. The strengthening effect of LPSO phase was dominant over that from the grain refinement and texture. [Copyright &y& Elsevier]

CuO was coated on the surface of Al 18 B 4 O 33 whiskers by hydrothermal synthesis and CuO coated Al 18 B 4 O 33 whiskers reinforced 6061Al composites with different coating contents were fabricated by squeeze casting. The preparation process and characterizations of the CuO coated Al 18 B 4 O 33 whiskers were studied. The effects of CuO coating of whiskers on the microstructures, tensile properties and aging behaviors of the composite were investigated. The results showed that a uniform CuO coating of Al 18 B 4 O 33 whiskers could be prepared by hydrothermal synthesis. CuO reacted with molten 6061Al during squeeze casting and meanwhile a layer of continuous MgAl 2 O 4 formed at the interface. With increasing the contents of CuO coating on whiskers, the ultimate tensile strength of the composite gradually increased. The elongation to fracture of the composite initially increased and later decreased. Impressively, the ultimate tensile strength of the composite could be further improved after T6 heat-treatment. CuO coating of the whiskers could also obviously change the aging behaviors of the composite. [ABSTRACT FROM AUTHOR]

Tensile yield strength of extruded Mg–5.3Zn–0.5Ca–0.5Ce/La (weight percent) alloy is remarkably increased to 316 MPa from 163 MPa, via the warm rolling process. The tension twinning can be activated after low-strain (5–21%) rolling, and the dynamic recrystallization occurs with increasing rolling reduction. The dislocations are gradually accumulated within the original grains during the rolling, and the number fraction of low angle grain boundary is increased. The coarse secondary phases are gradually broken into small pieces, due to the increased rolling deformation. The weak fiber texture with 10 1 ̅ 0 parallel to extrusion direction in the extruded alloy is modified to the typical 0002 10 1 ̅ 0 texture after rolling, and the yield strength is notably improved, because of the multiple strengthening effects (grain refinement, work hardening, dispersion and texture). A good balance between strength (> 310 MPa) and ductility (~ 9.5%), has been achieved through the warm rolling. [ABSTRACT FROM AUTHOR]

As-cast Mg–5.3Zn–0.6Ca (weight percent) alloy was indirectly extruded at 300 °C with different deformation rates (ram speeds of 0.1, 0.3, 0.5 mms − 1 ), and the microstructure, texture and mechanical properties of the as-extruded alloys were investigated in the current study. With the increase of deformation rates, the average size and volume fraction of dynamic recrystallized grains were remarkably increased. The basal fiber texture became weak in the as-extruded alloy with higher volume fraction of recrystallized grains, because most of the basal planes in these grains were tilted to extrusion direction about 30–40°. The higher deformation rate decreased the tensile yield stress due to the grain coarsening and basal texture weakening, while the elongation was improved, which was resulted from the enhanced work hardening rate. [ABSTRACT FROM AUTHOR]

The yield strength of the extruded Mg−9.9Y−3.7Zn (wt%) alloy at room temperature is remarkably increased from 240 MPa to 364 MPa using low-stain rolling. This significant improvement is ascribed to the combination of intensive basal texture, fine long-period stacking ordered phase particles and a high density of dislocations. The elongation of the rolled alloy increases as the strain of rolling increases, which is attributed to the homogenous distribution of fine long-period stacking ordered phases. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a rare earth (RE) free Mg69Zn27Ca4 bulk metallic glass (BMG) of diameter 1.5mm was successfully fabricated by the injection casting method using recycled materials in atmospheric air. Without using high vacuum conditions, high purity starting materials and expensive rare earth materials, the findings of the work are of significance in reducing the cost and improving the manufacturability of BMGs. The results of the uniaxial compression tests further showed that there were no obvious differences between BMGs prepared under high vacuum or in atmospheric environment. The electrochemical polarization measurements in simulated physiological media revealed that the atmospheric Mg69Zn27Ca4 BMG manifested much lower passive current densities, higher pitting potential and a wider passive region than those of ZK60 and pure Mg alloys. The findings not only present Mg69Zn27Ca4 BMG as low cost material for potential biomedical applications, but also provide new insights into understanding of the effects of oxygen on glass formation. [Copyright &y& Elsevier]

Abstract: Indirect extrusion of as-cast Mg–5.25 Zn–0.6 Ca (wt%) alloy was performed at 300°C with different extrusion ratios (ER, 20:1 and 10:1), and the microstructure, texture and tensile properties of the as-extruded alloys were investigated in the current study. With the increase of ER, the volume fraction of DRXed grains was remarkably increased, but the average DRXed grains size was almost unchanged. The basal texture weakening phenomenon occurred in the as-extruded alloy with higher ER, which resulted from the higher volume fraction of the DRXed grain. Intensive basal fiber texture was observed in the unDRXed grains, but the basal planes of the DRXed grains were inclined to ED from 0° to 35°. The ER had only little effect on the tensile properties of the as-extruded alloys; due to the similar strengthening effect from the unDRXed and DRXed grains, a competitive mechanism exists between the fine grain strengthening and texture weakening effect. [Copyright &y& Elsevier]