7 research outputs found

    Unexpected formation of hydrides in heavy rare earth containing magnesium alloys

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    AbstractMg–RE (Dy, Gd, Y) alloys show promising for being developed as biodegradable medical applications. It is found that the hydride REH2 could be formed on the surface of samples during their preparations with water cleaning. The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments. It increases with the increment of RE content. On the surface of the alloy with T4 treatment the amount of formed hydride REH2 is higher. In contrast, the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys. Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water. The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides

    Recent research and developments on wrought magnesium alloys

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    Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys. In this contribution, recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design, focusing on Mg-Al, Mg-Zn and Mg-rare earth (RE) systems. The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms, e.g. grain refinement, precipitation and texture hardening effect. Finally, the new alloy design and also the future research of wrought magnesium alloys to improve their mechanical properties are discussed. Keywords: Wrought magnesium alloys, Alloy design, Mechanical propertie

    Strengthening and ductilizing of magnesium alloying with heavy rare earth elements

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    Among all alloying elements the rare earth elements (RE) play a key role in improving the ductility, high temperature strength and corrosion resistance effectively for magnesium and its alloys. The present work investigated the influences of single alloying or multi heavy REs (Gd, Dy and Y) alloying on the strengthening and ductilizing of magnesium. These heavy REs have a higher solid solubility in magnesium than that the light REs such as Nd and Ce. It is found that the solid solution strengthening caused by Gd follows the linear relationship with the exponent n value of 1/2 or 2/3. When adding two or more heavy REs in Mg, owing to their interactions and resultant synergetic effects, the effectiveness of strengthening and ductilizing caused by multiple RE addition is much better than that by single RE addition

    In situ compressive investigations on the effects of solid solution Gd on the texture and lattice strain evolution of Mg

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    The present work studies the effects of solid solution Gd on the texture and lattice strain evolution of an extruded Mg15Gd alloy under uniaxial compression. In situ experiments were carried out using high energy X-ray diffraction on samples of the investigated materials with three different orientations. The original textures of the pure Mg and the Mg15Gd alloy exhibit basal planes that are preferentially parallel and perpendicular to the extrusion direction (ED), respectively. The c/a ratio of the Mg15Gd alloy decreases with increasing Gd content in the solid solution, leading to a different deformation behavior compared with pure Mg under the compressive load. The addition of Gd enhances the slip and twinning modes. However, prismatic slip is activated earlier in the Mg15Gd alloy due to the lower c/a ratio

    Influence of the amount of intermetallics on the degradation of Mg-Nd alloys under physiological conditions

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    The influence of amount of intermetallics on the degradation of as-extruded Mg-Nd alloys with different contents of Nd was investigated via immersion testing in DMEM+10% FBS under cell culture conditions and subsequent microstructural characterizations. It is found that the presence of intermetallic particles Mg41_{41}Nd5_5 affects the corrosion of Mg-Nd alloys in two conflicting ways. One is their negative role that their existence enhances the micro-galvanic corrosion. Another is their positive role. Their existence favours the formation of a continuous and compact corrosion layer. At the early stage of immersion, their negative role predominated. The degradation rate of Mg-Nd alloys monotonously increases with increasing the amount of intermetallics. Mg-5_5Nd alloy with maximum amount of intermetallics suffered from the most severe corrosion. With the immersion proceeding (≥7 days), then the positive role of these intermetallic particles Mg41_{41}Nd5_5 could not be neglected. Owing to the interaction between their positive and negative roles, at the later stage of immersion the corrosion rate of Mg-Nd alloys first increases with increasing the content of Nd, then reaches to the maximum at 2 wt. % Nd. With a further increase of Nd content, a decrease in corrosion rate occurs. The main corrosion products on the surfaces of Mg-Nd alloys include carbonates, calcium-phosphate, neodymium oxide and/or neodymium hydroxide. They are amorphous at the early stage of immersion. With the immersion proceeding, they are transformed to crystalline. The existence of undegradable Mg41_{41}Nd5_5 particles in the corrosion layer can enhance the crystallization of such amorphous corrosion products
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