Effect of milling time on the mechanical properties of zirconia toughened alumina composites

Abstract

Due to high reliability, longer useful life and sustainability in harsh environment, zirconia toughened alumina (ZTA) are prominent composite used by multifarious industries. In general, the components of ZTA are fabricated through powder metallurgy route consisting of various steps like milling, compaction, sintering, post polishing etc. Every step has propounded its dire effect on the mechanical properties. A lot of investigations are dedicated on thermal effect, but very little research is available on the milling of powders before densification. Therefore, this study discloses the effect of milling time on the bulk density, hardness and fracture toughness of ZTA composite. Co-precipitation process is opted to fabricate the ZTA composites. The synthesized ZTA composites are milled for five different time period i.e. 30, 60, 90, 120 and 150 min. A significant effect of milling time is observed on the mechanical properties. In case of, bulk density an improvement is noticed upto the optimal grain size. Beyond that the bulk density decreases, due to the inferior compaction resulting in high porosity inside the matrix. The evaluated value of hardness resembles same trend of bulk density due to direct relationship. The fracture toughness shows continuous increment with increase in milling time, but significantly improvement is noticed at high milling time. The said result may be attributed to the presence of high porosity inside the cluster of composite.