WEAR MECHANISM OF XD(TM) ZL201 TIB2 IN-SITU COMPOSITE

The microstructure and dry sliding wear behaviour of XD(TM) ZL201-TiB2 in situ composite were studied by scanning electron microscopy, trans mission electron microscopy, X-ray diffraction, pin-on-ring friction a nd wear testing. The microstructural constituents of the ZL201-TiB2 co mposite aged at 175 degrees C for various ageing times were found to b e dispersive submicrometre TiB2 particles, fine theta'', theta'-precip itates and a-Al solid solutions. As contrasted to the unreinforced ZL2 01 alloy, the ZL201-TiB2 composite possessed a higher microhardness an d wear-resistance as well as a shorter ageing time for peak hardness. With the increase of sliding distance, transition of the dominant wear mechanism for the ZL201-TiB2 composite occurred from adhesive wear to fatigue wear in sliding contacts. At the earlier stages of wear, adhe sive wear characteristics featured by mild scratchings and plastic sme aring were observed on the worn surface and platelet-type wear debris; but at the later stages, contact fatigue failure of a relatively thic k surface layer in relative motion, which revealed a build-up of layer -like structure and the presence of spherical particles of debris, bec ame the dominant factor for the removal of composites. (C) 1998 Chapma n & Hall.