Dec 24, 2016 - By comparing ZTA ceramics with and without addition of MgO the result found an ..... Journal of Alloys and Compounds (2010) 497(1):316-320.
Available online at www.icemme.com Proceedings of the
1st International Conference on Engineering Materials and Metallurgical Engineering 22- 24 December, 2016
Bangladesh Council of Scientific and Industrial Research (BCSIR) Dhaka, Bangladesh
EFFECT OF MgO ADDITION ON THE PHYSICAL AND FRACTURE BEHAVIOR OF ZIRCONIA TOUGHENED ALUMINA Md. Abdullah Al Mahmooda*, M.A. Gafurb, M.E. Hoquea, M.R. Qadirb, Muhammad Shahriar Basharb a
Rajshahi University of Engineering & Technology, Rajshahi 6204, Bangladesh Bangladesh Council of Scientific and Industrial Research, Dhaka, Bangladesh
b
Abstract The effects of MgO addition on the phsical and mechanicalproperties such as density, porosity, microstructure, Vickers hardness, and fracture toughness of ZTA ceramics composites were investigated. The amount of ZrO2 used in the experiment was fixed at 15 wt% while the MgO addition was varied from 0 wt% to 1.5 wt%. Each composition was weighed, mixed, and pressed using hydraulic press under 300 MPa into 10 mm pellets. The pellets were sintered at 1450°C, 1520°C and 1590°C for 5 hours under pressureless condition. Vickers hardness and fracture toughness of the sintered samples were measured using the Vickers indentation method. Other properties like as density and porosity was also measured. XRD and SEM analysis was carried out to examine the presence and effect of MgO on the properties of ZTA. By comparing ZTA ceramics with and without addition of MgO the result found an increasing of fracture toughness and hardness of the materials. The optimum amount of addition of MgO was found 1-1.5% depending upon sintering temperature bellow 1600°C. Keywords: Zirconia Toughened Alumina; MgO; Vickers hardness; Fracture toughness
INTRODUCTION Zirconia Toughened Alumina (ZTA) provides mechanical strength and wear resistance and is used as the ideal intermediate solution between Zirconia and Alumina [1]. The main advantage of Zirconia Toughened Alumina (ZTA) is the additional strength and toughness over alumina [2]. Zirconia Toughened Alumina (ZTA) ceramics offer an exceptional performance to price ratio. Like Yttria Stabilized Tetragonal Zirconia Polycrystal (YTZP), Zirconia Toughened Alumina (ZTA) belongs to a family of ceramics that have a toughening mechanism due to transformation of the crystal structure under an applied stress. Their microstructures have been tailored to produce a significant enhancement of structural properties over basic alumina materials. These improved properties are the result of a combination of factors, most significantly a phenomenon known as “transformation toughening”. ZTA’s carefully tailored microstructure with a uniform dispersion of YTZP particles in an alumina matrix results in a more fracture resistant structure than alumina alone [3]. Regardless of their advantages, ceramic materials exhibit very low toughness which eventually limits their overall applications [4–8]. The use of ZrO2-based ceramics is one of the possible alternatives to circumvent the limitation of low fracture toughness [9, 10]. Most investigators concluded that a optimum amount of zirconia should be in the turn of 8-15 vol%( in ZTA) considering a trade-off between improvements in fracture toughness, decrease grain size and lower hardness [11-14]. Beside all advantages of using ZTA, it is difficult to have ZTA with high density and always the reported bulk density of ZTA is lower than mono phase ceramic of alumina and zirconia which lead to lower definitive properties in applied engineering in the compare with research studies [11,14,15]. There exist many possible additives, mainly metal oxides which, with various efficiencies, act as sintering aids and grain growth inhibitors for alumina and in limit cases they are used for ATZ. One of the most used and also one of the most effective is magnesia (MgO). Because of its efficiency, very small amounts of MgO are needed for good densification and to limit abnormal grain growth during sintering [11,13,14,16-18]. Azhar et.al. and Rejab et.al. [19-21] suggested that a small amount of MgO addition to the ZTA can improve its hardness and microstructural properties. Also it can help to reduce the sintering temperature of ZTA and helps to inhibit the
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Abdullah Al Mahmood/ Proceedings of the 1 ICEMME, 22-24, Dec, 2016, Dhaka,Bangladesh
agglomeration and abrupt grain growth of Al2O3. In this work small amount of MgO (0-1.5 wt%) added to the Alumina and Zirconia nanopowder to achieve better physical and mechanical properties. MATERIALS AND METHODOLOGY The commercially available powders used in this work were the α-alumina powder (Nanocrystalline, crystal size 40nm, particle size 150nm) , Yttria-stabilized zirconia (3 mol%, Purity 99.9%, particle size
