Effect of ZrO2 and MgO added in alumina on the physical and mechanical properties of spark plasma sintered nanocomposite

Abstract

The aim of the present research work was to investigate the effect on the properties such as density, surface roughness, microhardness, fracture toughness and microstructure added with MgO and ZrO2 in an alumina matrix. The magnesia-zirconia toughened alumina spark plasma sintered nanocomposite samples were developed successfully and found the suppressing grain growth and crack free microstructure. No damage was found due to thermal shock up to 1350 °C. The amount of ZrO2was added with 5 vol%, 10 vol% and 15 vol%, while MgO added with 0.5 vol%, 1 vol% and 2 vol% in an aluminamatrix. Each composition was weighed and mixed together. After that, the powders were pressed under the rapid heating at the sintering temperature of 1250 °C, 1300 °C and 1350 °C and for 5 min holding time under pressure of 60 MPa simultaneously. The optimum properties were found with the compositions of 10 vol% of ZrO2, 1 vol% of MgO in the Al2O3 matrix. It showed highest relative density (99.68%), minimum surface roughness (1.123 μm), highest microhardness (19.46 GPa) and minimum average grain size (0.595 μm). The highest fracture toughness was found to be 6.7 MPa.m1/2 the added with 15 vol% of ZrO2,1 vol% of MgO in the Al2O3 matrix for the holding time 5 min and a sintering temperature of 1300 °C. The X-ray diffraction analyses indicate the presence of major phases were ZrO2, α-Al2O3, MgO, magnesia phase with minor peaks of the secondary phase MgAl2O4. This was found due to chemical reactions between the composite constituents present in the matrix during the sintering. Uniform microstructure was observed using a field emission scanning electron microscope and obtained the sub-micron level of grain size without any significant increases of grain size. The developed compositehas high hardness and toughness to make it more suitable for applications such as ballistic armor and thermal barrier coating.