Ultrasonically aided laser drilling of particle reinforced aluminium based composites

An ultrasonically aided laser drilling technique has been developed to raise the performance of traditional laser drilling on metal matrix composite materials. In the process, the workpiece is rigidly attached on top of a transducer which vibrates at a frequency of 20 kHz. Ultrasonic vibration has significantly increased liquid expulsion in laser drilling. For blind hole drilling of an aluminium alloy 2124/SiC composite, the thickness of the recast layer was reduced greatly by about 30-80% at different segments of the hole. In the recast layer the size and the amount of carbides were reduced when vibration was employed. Moreover the depth of drill can be increased by as much as 20% when vibration was used. In through hole drilling of some 0.6-1.2 mm thick materials the recast layer was virtually removed and a reduced heat affected zone was obtained with no apparent deposition found at either end of the hole. Also the diameter of the through hole became more uniform.