Dual-frequency ultrasonic treatment on microstructure and mechanical properties of ZK60 magnesium alloy

Publication date: January 2018
Source:Ultrasonics Sonochemistry, Volume 40, Part A
Author(s): Xingrui Chen, Fangkun Ning, Jian Hou, Qichi Le, Yan Tang
Compared with other dual-frequency acoustic applications, melt-treatment with dual-frequency ultrasound was less researched, especially in magnesium field. In this present work, traditional single-frequency ultrasonic field (SUF) treatment and dual-frequency ultrasonic field (DUF) treatment were used to refine the as-cast microstructure and improve the mechanical properties of the ZK60 (Mg–Zn–Zr) magnesium alloy. The influences of DUF on the microstructure evolution and mechanical properties were systematically investigated, and the cavitation bubble's dynamic behaviors were investigated by numerical simulation. α-Mg grains and second phases were dramatically refined by introduced ultrasound, and DUF showed higher refinement efficiency than SUF. The DUF treatment promoted the formation of small α-Mg globular grains and changed the distribution and morphology of MgZn2 phases. Mechanical properties of the as-cast alloy were much promoted with DUF. Yield strength, ultimate tensile strength and elongation increased to 153MPa, 239MPa and 13.9% respectively after 1400W DUF treatment, which were 30.8%, 42.3% and 58.0% higher than the values obtained from untreated samples and 20.5%, 20.7% and 30.0% higher than 1200W SUF treated samples. The DUF can generate more and larger cavitation bubbles, and make more bubbles into instantaneous bubbles, improving refinement efficiency.



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