2012 Volume 53 Issue 2 Pages 417-424
For the development of nondestructive detection method of casting defects in SiC particulate-reinforced Al–Si alloy composite (the MMC castings), plates of the alloy composite and the Al–Si alloy were cast, and holes of different diameters were introduced at different depths. Then the ultrasonic measurement was carried out in water with the longitudinal waves of 5 and 10 MHz in frequency by the normal incidence, and also with the surface acoustic wave (SAW) of 5 MHz in frequency. The hole of 2 and 1 mm in diameter or larger was detected at a depth of 2 to 10 mm below the surface of the MMC castings and the Al–Si alloy castings, respectively, by the normal incidence. And the hole of 2 mm in diameter or larger was detected at a depth less than 1 mm below the surface of the MMC castings by the SAW measurement. The reflection intensity from the hole in the MMC castings took a far lower value than the DGS curve. The DGS curve was modified in consideration of scattering of the ultrasonic wave by cast structures and casting defects, and took a similar tendency with the reflection intensity form the hole. Then, plates of MMC castings were subjected to X-ray radiography and ultrasonic measurement, and the depth of pores and shrinkage cavities of more than 2 mm in size were estimated by the ultrasonic measurement successfully.
