Microhardness, Young's modulus and fracture toughness of alumina implanted with Zr+, Cr+, Ti+ and Ni+. The effect of the residual stresses

Ion implantation is known to be capable of modifying the surface and near-surface chemical and mechanical properties of solids pertaining to hardness, elastic modulus and fracture toughness. In this study polycrystalline alumina was implanted with Zr+, Cr+, Ti+ and Ni+ ions (110 keV) to a dose of 1017 ions/cm2 at room temperature. Mechanical properties such as hardness and Young's modulus were determined using ultra-low load microindentation hardness tester. With the Vickers indentation method, using different loads, the fracture toughness of the implanted layer was determined. The nature of the chemical phases were characterized by X-ray photoelectron spectroscopy (XPS). Implantation caused an increase in the hardness and the fracture toughness with no detectable effect on the Young's modulus. These modifications were attributed to microstructural changes caused by the implantation. The residual stresses were determined by a previously described indentation technique. They were found to be compressive in nature and ranged from 800 to 1800 MPa. (Author)