Papers by Author: Yan Long Ma

Abstract: The effects of different solid solution and aging technologies on the microstructure of AM50 were studied. The results indicated that heat-resistant Al-Mn phases were the major second phases in AM50 alloy under all testing conditions. Highest microhardnesses were obtained not only in as-aged sample but in as-solution treated sample, which indicated that the strengthening mechanism for AM50 alloy was not limited to precipitation reinforcement.

Abstract: The latest research results on new types of magnesium alloys containing strontium or rare earth elements are reviewed. Special attentions are paid to the alloying design, microstructure and properties controlling, the influence of minor addition of Sr and RE on the microstructure and properties of existing magnesium alloys. Some new types of magnesium alloys containing Sr or RE are introduced and discussed.

Abstract: In this paper, the effects of Sb and RE on the solutionized microstructure and microhardness of Mg-6A1-1Zn-0.7Si magnesium alloy are investigated. The research results indicate that the solid solution treatment can result to the modification of Chinese script shaped Mg2Si phases in the microstructure of experimental alloy, and adding small amounts of RE and Sb can strengthen the modification efficiency. In addition, after the solid solution treatment at 420°C, the Mg-6A1-1Zn-0.7Si alloy added 0.4%Sb and 0.25%RE exhibits higher microhardness, but the effect of Sb and RE additions on the changing law between microhardness and solutionized time, is not obvious.

Abstract: In the present paper, nine kinds of alloys with different contents of zinc and zirconium were cast and the influence of zinc and zirconium individually and jointly on the microstructure of the ZK alloys were investigated. The results indicated that the shape and amount of the eutectic were closely related to the content of Zn. With the increase of Zn content, the eutectic was prone to have fish-bone-like shape. When the eutectic grew up to contact with each other, then network eutectic formed; Zr could intensively refine not only the grain size but also the eutectic, but when Zr>0.6%, compound containing Zr or pure Zr granules would appear. That the increase of the Zn must go with the increase of the Zr proved the combined influence of the two alloy elements.

Abstract: This paper reviews the latest research and development status of processing technologies for wrought magnesium alloys including extrusion, forging, (twin-roll) thin strip casting, rolling, stamping, and superplastic forming. Existing problems and the development trends of these processing technologies are analyzed and discussed. Up to the present, the R&D on the processing technologies of wrought magnesium alloys has made great global progress. Nevertheless there is a long way to achieve large-scale industrialization and application of wrought magnesium alloys.

Abstract: Morphologies of precipitation phases along grain boundaries of the as-cast Mg-6.0Zn-0.45Zr, Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys were investigated. The experimental results indicated that the main precipitation phase along grain boundary of the as-cast Mg-6.0Zn-0.45Zr was a Mg-Zn binary compound. There were two kinds of precipitation phases along grain boundaries for Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys. One grew at triangular grain boundary, which was fish-bone -like in shape and a Mg-Zn binary compound. The other distributed mainly around the grain, which was net-like in shape and a Mg-Zn-Y ternary compound. In addition, there were lots of granular phases, extending to the interior of the grain, at the rim of grain boundary phases. Y was found to affect obviously morphology of precipitation phases along grain boundary of the as-cast Mg-Zn-Zr (ZK60) alloys.

Abstract: Alloy phases in the as-aged (T6) ZK60 magnesium alloy were investigated. More attentions were paid to types and morphologies of main alloy phases in the as-aged ZK60 magnesium alloy. The experimental results indicated that there was an abundant flower-shaped segregation in the solution-treated ZK60 magnesium alloy. A small quantity of undissolved compounds, MgZn2, was also found. They distributed irregularly in the form of similar parallelogram, with a dimension of 200nm~500nm and not sensitive to heat-treatment. Mg2Zn3 was found to be a main secondary compound in the as-aged ZK60 alloy, which precipitated during aging. Another precipitation phase, MgZn, in the as-aged ZK60 magnesium alloy was also found in the form of long and thin rods with a dimension of 500nm.