Microstructure and Mechanical Properties of Light Multi-component Alloys

• Main Author: 洪楨雄
• Other Authors: 金重勳
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/93021404940631970985

碩士 === 國立清華大學 === 材料科學工程學系 === 93 === The aim of this research is to develop light and high strength multi-component alloys with a density below 5 g/cm3. The major constituent elements of these multi-component alloys are Al, Be, Si, Ti, Y, that has a density below 5 g/cm3. Except for the major composition series, Si free series, Be free series and heavy elements (V and Zr) modified series were also investigated. These alloys were prepared by arc melting and their microstructure, hardness, and thermal properties were studied. The results showed that the alloys form a major FCC solid solution and two precipitations, silicides and the Y-Al compounds, randomly distributed over the matrix . In Si free series, it was observed that the alloys have two main phases forming drop-lets in each other. In Be free series, there are silicides distribution over the matrix. Among all the alloys, the composition, AlBeSiTiVY, exhibits the highest hardness of HV860. This may originate from the solid solution strengthening and precipitation hardening mechanisms. Over all 5-element alloys, AlBeSiTiY, exhibits the highest hardness above HV700. The hardness of Be free series is higher than that of Si free series. From the DTA analysis, it was found that all alloys are stable at high temperature of 1400 oC except for Si free series. The alloys, AlBeTiVY and AlBeTiVYZr, partly melted at 1000 oC. The density of all of the alloys is lower than 5 g/cm3, and the ratio of hardness to density is larger than 40, except AlBeTiVYZr. They are highly strengthened alloys. For instance, the ratio of hardness to density of the aluminum alloy, 7075 – 6T which is the hardest alloy in aluminum alloys, is 18.3. The ratio of 7075 - 6T is lower than that of high-entropy alloys, AlBeSiTiY-V,Zr. Therefore, it is very potential for industrial applications such as cutting tools, structural materials and wear resistance surface.