Nondestructive Detection of Cold Flakes in Aluminum Alloy Die-Cast Plate with Ultrasonic Measurement

Abstract

Aluminum alloy die-cast plates (ADC 12) were subjected to ultrasonic measurement to obtain a relation between the intensity distribution of the ultrasonic wave and positions of cold flakes appearing in the plate for developing a nondestructive method to detect cold flakes in the diecasts. Die-cast plates of 170 mm in length, 50 mm in width and 6.8 mm in thickness were produced with wider gates to introduce larger cold flakes in the plate. Then the ultrasonic measurement was carried out with the immersion method by using a probe generating a longitudinal wave of 20 MHz in frequency. Intensity distributions of the ultrasonic wave were obtained from the surface to the bottom. The cross section analysis was carried out to examine the distribution of the cold flake. From the cross section analysis, three types of cold flakes were observed: the type A with a straight boundary of initial solidification with oxide thin layer, the type B with a straight boundary without oxide layer, and the type C of an irregular and wavy boundary without oxide layer. In the case of the type C, the oxide layer was thought to be out of the observed section. The ultrasonic wave was slightly reflected from the front and rear boundaries between the cold flake and the matrix, and it was found that the position and the thickness of the cold flake can be detected by ultrasonic measurement.

Noncontact Laser Ultrasound Detection of Cracks Using Hydrophone

“…Typically, there are two types of noncontact ultrasonic techniques: water immersion ultrasonic [ 11 , 12 , 13 , 14 , 15 , 16 ] and noncontact laser ultrasonic. The water immersion ultrasonic technique is mostly performed on small objects with uneven surfaces.…”

OS4-5-1 Influence of Cold Flake on the Fatigue strength of Aluminum alloy Die-Cast ADC12

“…Recently, the authors [4,5] carried out the ultrasonic measurement and the acoustic microscopy of aluminum alloy die-cast (ADC12) plates containing cold flakes, to show that the oxide layer and the body of the cold flakes can be detected as bright or dark regions in the acoustic image, respectively.…”

Influence of Casting Defects on Tensile Properties of ADC12 Aluminum Alloy Die-Castings

“…27) Although many efforts have been done to eliminate cold flakes, no success has been attained to eliminate them completely from die-cast products. 28) Recently, the authors 29,30) carried out the ultrasonic measurement and the acoustic microscopy of aluminum alloy die-cast plate (ADC12) containing cold flakes, and it was found that the oxide layer and the body of the cold flake were observed as bright and dark regions in the acoustic image, respectively. The authors 30) also carried out the bending test, and showed that a crack propagated through the coarse cold flake directing transversely to the bending stress.…”