Influence of ZrB₂/hBN particles on the wear behaviour of AA7075 composites fabricated through stir followed by squeeze cast technique

Abstract

This paper reports on the effect of ZrB2 and hBN solid lubricant particles on the dry sliding wear behaviour of the AA7075 composite, fabricated by stir-squeeze cast technique. ZrB2 and hBN at levels of 5 wt% were chosen as reinforcements for the study. The optical microscope images revealed uniform distribution of particles and a low order of porosity in microstructure, possibly due to the squeeze pressure. The ZrB2 particles reinforced composite (AZ) showed an improvement in hardness compared to as-cast (A0) and hBN containing composite (AH). A minor reduction in the hardness of ZrB2–hBN hybrid composite (AZH) was observed. This is attributed to changes in the hardness induced by the individual ZrB2 and hBN particles. The hybrid composite (AZH) exhibits a superior wear resistance, possibly due to the formation of good quality B2O3 and H3BO3 self-lubricating film.

Tribological behaviour of AZ91D/ultra-high-temperature ceramic composites at room and elevated temperatures

“…This was due to the abrupt disturbance of the oxide layer, which further breaks as the sliding distance progresses. 13 It can be further noted that the COF of composites is decreasing with an increase in wear testing temperature. As shown in Figure 12(b), the COF of ATB has the least value, followed by ATC and ATN.…”

“…The combination of stir–UST–squeeze casting processes increases the wettability of matrix particles, facilitates degassing, eliminates ceramic particles agglomeration, and disperses them in the matrix homogeneously. 10–13…”

“…Such uniformly distributed particles refine the grain structure and resist local plastic deformation of the matrix during indentation. 10,13 It should be noted that the application of squeeze pressure prevents the formation of micropores resulting in an increase in hardness of materials. 32 Although the hardness values of the three composites are almost equal, the hardness of ATB is slightly large.…”

“…11 At present, much attention has been paid to the stir-squeeze casting process with the aid of UST for the manufacturing of composites. 12,13…”

“…11 At present, much attention has been paid to the stir-squeeze casting process with the aid of UST for the manufacturing of composites. 12,13 Many studies focused on the use of titanium compounds as reinforcements in various Mg composites produced through various manufacturing techniques are described in the existing literature. Anasori et al 14 stated that due to the incorporation of TiC (54 ± 2 vol.%) by a pressureless melt infiltration process, the hardness and grain size of AZ91D matrix composite were significantly enhanced.…”