Dependence of nonlinear ultrasonic characteristic on second-phase precipitation in heat-treated Al 6061-T6 alloy

Jongbeom Kim; Kyung-Young Jhang; Chungseok Kim

doi:10.1016/j.ultras.2017.07.015

Dependence of nonlinear ultrasonic characteristic on second-phase precipitation in heat-treated Al 6061-T6 alloy

Ultrasonics. 2018 Jan:82:84-90. doi: 10.1016/j.ultras.2017.07.015. Epub 2017 Jul 21.

Authors

Jongbeom Kim¹, Kyung-Young Jhang², Chungseok Kim³

Affiliations

¹ School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
² School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea. Electronic address: kyjhang@hanyang.ac.kr.
³ Department of Metallurgy and Materials Engineering, Chosun University, 309, Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea.

PMID: 28783487
DOI: 10.1016/j.ultras.2017.07.015

Abstract

It is well known that nonlinear ultrasound is sensitive to certain microstructural features in materials such as dislocations and precipitates. This paper investigates the dependence of the nonlinear ultrasonic characteristic on Mg_nSi_m precipitation in heat-treated Al 6061-T6 alloy specimens. The specimens were heat-treated at a constant temperature of 220°C for different exposure times up to 6000min. The accuracy of the ultrasonic measurement setup that determines the absolute ultrasonic nonlinearity parameter β_u was first validated. The nonlinearity parameter and the yield strength were measured for each of the artificially aged specimens. The experimental results show fluctuations in the nonlinearity parameter and yield strength over the aging time, but with an interesting correlation between the nonlinearity parameter and the yield strength over the aging time. Microstructural observations confirmed that those fluctuations are due to the formation and evolution of precipitates that occurs in a unique precipitation sequence in this alloy. These results suggest that the nonlinear ultrasonic measurement can be useful for monitoring second phase precipitation and related mechanical properties in the Al 6061-T6 alloy.

Keywords: Al 6061 alloy; Microstructure characterization; Nonlinear ultrasound; Precipitation hardening.

Publication types

Research Support, Non-U.S. Gov't