Modification of mechanical properties of Ti-Al intermetallic matrix by introducing TiB2 ceramic
Marek Kostecki, Andrzej Olszyna Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Quarterly No. 3, 2006 pages 65-70
DOI:
keywords: intermetallics, composites, fracture toughness
abstract Modification of mechanical properties of Ti-Al intermetallic matrix by introducing TiB2 ceramic The study is concerned with improving the mechanical properties of TiAl (α2+γ) by introducing ceramic particles of titanium diboride (TiB2) into its matrix. The material examined was prepared of the TiAl powder (manufactured by the Alfa Aesar) and the TiB2 powder (delivered by the Borax Consolidated Ltd), of a purity of 99.5%. The average size of the TiAl and TiB2 particles was 12.7 μm and 1.6 μm, respectively (Fig. 2). The powders were mixed by homogenizing in an agate mill filled with ethanol, to produce mixtures of various weight proportions: TiAl+xwt.%TiB2 with x = 0, 10, 20, 30, 40 wt.%, by homogenizing in an agate mill filled with ethanol. After drying, the powders were granulated and subjected to uniaxial pressing under a load of 20 MPa and then again pressed under isostatic pressure of 120 MPa. The samples were sintered under a pressure of 35 MPa (HP) in an argon atmosphere at the temperature T = 1250°C for 1 h. After sintering, the composite shows a high relative density 95÷98% (Fig. 4), hardness of 514 HV30 (Fig. 5) and a high stress intensity factor KIC = 16 MPa⋅m1/2 (value obtained for the TiAl+10wt.%TiB2 composite) (Fig. 6). The increased strength of the TiAl+10wt.%TiB2 composites can be attributed to the presence of the TiB2 ceramic grains. The hardening occurs as a result of the cracks formed in the ceramic phase particles being deflected and bridged (Fig. 7).