Abstract
In the aluminium-silicon system, eutectic alloys (about 13%Si) and hyper eutectic alloys (17∼23%Si) in particular show good high-temperature strength, comparatively small coefficients of thermal expansion and good anticorrosive properties. These alloys are therefore, rare of increasing concern for piston and other uses. In machining these alloys, however, it is difficult to obtain good cut surfaces and, especially, the hyper-eutectic alloys show severe tool wear. In this study, the hot machining is applied to these high silicon aluminium alloys for the improvement of their machinability. The turning tests are conducted on these alloys by varying the heating temperatures between 100 and 300°C at the beginning of cutting tests by gas heating. In addition, the orthogonal cutting tests of plate-type specimens are performed to compare the obtained results.
The shear stress on the shear plane decreases and the cutting resistance decreases with increasing heating temperature. As the heating temperature and the silicon content increase, the rate of increase of shear angle becomes higher and, in addition, the formation of a built-up edge decreases with improvement of the cut surface. When the temperature of the tool edge is over 500°C, however, the tool wear progresses severely in hype-eutectic alloys.
