Kim Jongbeom, Jhang Kyung-Young, Kim Chungseok
School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
Ultrasonics. 2018 Jan;82:84-90. doi: 10.1016/j.ultras.2017.07.015. Epub 2017 Jul 21.
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 MgSi 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 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.
众所周知，非线性超声对材料中的某些微观结构特征（如位错和析出物）敏感。本文研究了热处理后的Al 6061-T6合金试样中非线性超声特性对MgSi析出的依赖性。试样在220°C的恒定温度下进行不同时长（最长6000分钟）的热处理。首先验证了用于确定绝对超声非线性参数β的超声测量装置的准确性。对每个人工时效试样测量了非线性参数和屈服强度。实验结果表明，随着时效时间的延长，非线性参数和屈服强度存在波动，但在时效时间内非线性参数和屈服强度之间存在有趣的相关性。微观结构观察证实，这些波动是由于该合金中独特析出序列中析出物的形成和演变所致。这些结果表明，非线性超声测量可用于监测Al 6061-T6合金中的第二相析出及相关力学性能。
