Introduction of ultrasonic testing for root flaw imperfection on friction stir welding of aluminum alloys and magnesium alloys (JISZ3083)

Abstract

　Friction stir welding (FSW) is applied to various types of aluminum alloy structures because this weld method has many features. It's expected to be applied to magnesium alloy structures. However, practical ultrasonic inspection method to detect micro sized flaw in FSW was not developed. In the beginning of the evaluation, we prepare FSW test samples with 0 mm, 0,1 mm and 0,2 mm high root flaw, which includes incomplete penetration and lack of penetration, made by aluminum alloy and magnesium alloy. We applied a usual phased-array ultrasonic inspection method and a new type of the phased-array TFM/FMC (Total Focusing Method and Full Matrix Capture) method as the practical ultrasonic nondestructive inspection methods to detect root flaw in FSW. In the first step, we confirmed that the above two inspection methods basically enable to detect 0 mm, 0.1 mm and 0.2 mm high root flaws in the above FSW samples by using manual scanning of linear-array probes, whose frequencies are 10 MHz (32 channels) and 15 MHz (64 channels). Secondly we applied the phased-array TFM/FMC method to evaluate scanning profile of the ultrasonic echo intensity of 0 mm, 0.1 mm and 0.2 mm high root flaws by using manual scanning of the same probes with contact method. As a result of the above evaluation, we confirmed the possibility to identify 0.1 mm and 0.2 mm height root flaw. We also developed a draft JIS document for Ultrasonic flaw detection inspection method for root flaw in FSW of aluminum alloy and magnesium alloy. It was published as JIS Z 3083 in the end of 2018.