Effect of Mg 2 Si particles on the elevated temperature tensile properties of squeeze-cast Mg-Al alloys
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Communications Effect of Mg2Si Particles on the Elevated Temperature Tensile Properties of Squeeze-Cast Mg-Al Alloys MIN SOO YOO, KWANG S. SHIN, and NACK J. KIM Magnesium alloys are the lightest structural alloys commercially available and have great potential for applications in aerospace and automotive industries.[1,2,3] One of the major issues for Mg alloys has been obtaining the optimum combinations of strength, toughness, and corrosion resistance.[4–7] However, in recent years, improving the elevated temperature properties has become a critical issue for possible applications of Mg alloys in hot components.[8–20] The most common way of improving the elevated temperature properties is the use of thermally stable dispersoids. It has been shown that the addition of rare earth elements forms the thermally stable dispersoids in Mg matrix and improves the elevated temperature properties of Mg alloys.[11–14] However, these elements are expensive, limiting widespread application of such alloys. Recently, other relatively low-cost Mg alloys have been developed, which have good elevated temperature properties. These include, for example, Mg-Al-MnCa,[21,22,23] Mg-Al-Sr,[13,24] and Mg-Al-Zn-Sb[18,19] alloys. As evidenced by the popularity of Mg-Al-Si (AS) alloys, Si addition also improves the elevated temperature properties of Mg alloys.[25] However, Si addition often promotes the precipitation of Mg2Si particles in Chinese script form,[17] which has a deleterious effect on ductility and toughness. Recently, it has been shown that the addition of Ca or P modifies the morphology of Mg2Si particles from the originally Chinese script type to the polygonal type, resulting in an improvement in room-temperature strength and ductility.[17,26] It is expected that these modified Si containing alloys will have improved elevated temperature properties because Mg2Si particles are thermally stable and have favorable morphology such as polygonal shape and homogeneous distribution in the Mg matrix. In the present study, the effect of polygonal Mg2Si particles on the elevated temperature tensile properties of squeeze-cast Mg alloy is investigated and compared with the effect of other second-phase particles such as Mg17Al12 present in the commercial AZ91D alloy. Table I shows the compositions of the AZ91D alloy and the AZ61-Si-P alloy, which is the P-modified Si-containing alloy. The AZ61-Si-P alloy was prepared by melting highpurity metals in an induction melting furnace under an Ar
MIN SOO YOO, formerly Graduate Student with the Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), is Senior Technical Staff Member, Hynix Semiconductor Inc., Ichon 467-701, Korea. KWANG S. SHIN, Professor, is with the Division of Materials Science and Engineering, Seoul National University, Seoul, Korea 151-742. NACK J. KIM, Professor, is with the Center for Advanced Aerospace Material, POSTECH, Pohang, Korea 790-784. Contact e-mail: njkim@ postech.ac.kr Manuscript submitted Octo
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