Effects of direct ultrasonic treatment on microstructure and elongation of semi-solid Sn-62Bi alloy

• Published in: China foundry 2015-05, Vol.12 (3), p.163-168
• Main Authors: Zheng, Hui-ting, Hu, Yong-jun, Li, Ren-jie, Yang, Hong-huan, Sun, Xiao-yan, Li, Zhi-hao
• Format: Article
• Language: English
• Subjects: Alloys; Degassing of metals; direct ultrasonic treatment; semi-solid; Sn-Bi; microstructure; elongation; Elongation; Liquids; Metallurgy; Microstructure; Properties; Semi-solid processing; Slurries; Structure; Tin; Tin base alloys; Ultrasonic treatment
• ISSN: 1672-6421; 2365-9459; 1672-6421

A new direct ultrasonic treatment（DUT） setup with the ultrasonic horn placed in the horizontal direction was developed and used in the preparation of semi-solid Sn-62 Bi slurry. The influence of DUT temperature on microstructure and properties of Sn-62 Bi alloy were studied. The test results of XRD showed that the semi-solid Sn-62 Bi alloy obtained by the DUT process exhibits pronounced preferential orientation of Bi（2 0 2）, Bi（-1 1 1）, Bi（-2 0 1）, Sn（1 1 0） and Sn（2 2 0） planes. Compared to the conventional liquid casting Sn-62 Bi alloy without DUT, it was discovered that the primary Bi blocks of semi-solid Sn-62 Bi alloy prepared with the DUT process distribute more homogeneously and are smaller. With the treatment by ultrasonic vibration in the semi-solid state for 120 s, the higher the primary Bi phase fraction in the slurry, the smaller the size of primary semi-solid Bi blocks formed after solidification. The average side length of the primary Bi blocks was from 30 μm to 80 μm. The elongation of Sn-62 Bi alloy treated by DUT for 120 s at 145 °C is 43.21%, reflecting a distinctly improvement by 129.10%, as compared to the conventional liquid casting Sn-62 Bi alloy without DUT. This indicates that DUT process could improve dramatically the ductility of Sn-62 Bi alloys content. The microstructure evolution mechanism of semi-solid Sn-62 Bi alloy slurry was also analyzed.