Ti3Al - ZrO2 composites
Krzysztof Biesiada, Andrzej Olszyna Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 3 No. 7, 2003 pages 182-186
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abstract The study is concerned with the modification of the properties of Ti3Al, in particular aimed at improving the fracture toughness of this material, by introducing ceramic particles of the tetragonal zirconium oxide (TZ-3Y) into its matrix. The technological operations involved in the production of the Ti3Al+x%ZrO2 composite are: mixing the starting powders, drying the mixture at T = 90oC, granulating, uniaxial pressing at p = 20 MPa, isostatic compacting at p = 120 MPa, and free sintering at T = 1400÷1550oC in vacuum or argon for 1 h or hot pressing at T = 1400oC, p = 35 MPa for 1 h (Fig. 3). The physical properties of the Ti3Al+x%ZrO2 composites thus produced, such as the density, porosity and absorptivity were determined using the hydrostatic method (Figs. 4-6). The phases identified in the Ti3Al+40wt.%ZrO2 composite by a qualitative phase analysis were: tetragonal and monoclinic (traces) zirconium oxides and hexagonal Ti3Al (Fig. 7). The strength properties of the composite, such as the hardness (HV) and fracture toughness, were also examined using the Vickers method (Figs. 9 and 10). The Ti3Al+x%ZrO2 (x = 0, 10, 20, 30, 40 wt.%) composites hot-pressed under a pressure of 35 MPa show a high hardness of 710 HV10 and a high stress intensity factor KIc of 45 MPa ⋅ m1/2 (the latter value was measured in the Ti3Al+40wt.%ZrO2 composite). The increased values of the strength parameters of the Ti3Al+x%ZrO2 composites can be attributed to the presence of the t-ZrO2 ceramic phase grains. The mechanisms responsible for the hardening observed in the composites can directly be related to the tetragonal-to-monoclinic phase transformation that takes place during the sintering. Key words: intermetallic phases, intermetallic-ceramic composites, fracture toughness