Structural and Mechanical Properties of Alumina-Zirconia (ZTA) Composites with Unstabilized Zirconia Modulation

Md Abdul Gafur,Md Zahangir Alam,Md Al-Amin,Md Saifur Rahman Sarker

doi:10.4236/msa.2021.1211036

Md Abdul Gafur, Md Zahangir Alam + Show 2 more

Open Access

https://doi.org/10.4236/msa.2021.1211036

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Abstract

Zirconia toughened alumina (ZTA) ceramics are very promising materials for structural and biomedical applications due to their high hardness, fracture toughness, strength, corrosion and abrasion resistance and excellent biocompatibility. The effect of unstabilized ZrO2 on the density, fracture toughness, microhardness, flexural strength and microstructure of some Zirconia-toughened alumina (ZTA) samples was investigated in this work. The volume percentage of unstabilized ZrO2 was varied from 0% - 20% whereas sintering time and sintering temperature were kept constant at 2 hours and 1580°C. The samples were fabricated from nanometer-sized (α-Al2O3: 150 nm, monoclinic ZrO2: 30 - 60 nm) powder raw materials by the conventional mechanical mixing process. Using a small amount of sintering aid (0.2 wt% MgO) almost 99.2% of theoretical density, 8.54 MPam? fracture toughness, 17.35 GPa Vickers microhardness and 495.67 MPa flexural strength were found. It was observed that the maximum flexural strength and fracture toughness was obtained for 10 vol% monoclinic ZrO2 but maximum Vickers microhardness was achieved for 5 vol% ZrO2 although the maximum density was found for 20 vol% ZrO2. It is assumed that this was happened due to addition of denser component, phase transformation of monoclinic ZrO2 and the changes of grain size of α-Al2O3 and ZrO2.

Highlights

All materials can be broadly classified into three categories: Metal, Ceramic and Polymer
The analysis reported that stabilized zirconia has a great effect on the mechanical properties
It has been seen that the density of the sintered body increases with increasing zirconia contentand the porosity decreases with increasing zirconia

Summary

Introduction

All materials can be broadly classified into three categories: Metal, Ceramic and Polymer. Strength, toughness and chemical inertness properties make it superior for the ceramic composites at temperature well above the melting temperature of alumina It needs to be stabilized for avoid cracking under stress conditions. If any stress is applied, the stabilized tetragonal phases of zirconia at room temperature change their phases into monoclinic with expanding their volume by absorbing the energy applied on them and stop the crack to propagate further which is referred to as stress-induced phase transformation of zirconia [7] Through applying this phase transformation mechanism, it increases the fracture toughness of the composite materials that are generally defined as the toughening mechanism.

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