FRICTION CHARACTERISTICS OF STIR-CAST AL-PB ALLOYS

The coefficient mu of friction of stir-cast Al-Pb alloys with different lead contents and with the same lead content but cast at different agitator speeds against carburized steel has been determined under dry sliding conditions in a Timken wear- and lubricant-testing machine. It is observed that mu remains almost steady with increase in load or sliding velocity for all the stir-cast Al-Pb alloys and commercially pure aluminum but for commercially pure lead it increases sharply with increase in load and sliding velocity. It has also been observed that mu decreases with increase in lead content in Al-Pb alloys until about 20 wt.% but, beyond this composition, it increases sharply. To understand the friction mechanism, the friction tracks are studied by scanning electron microscopy.