Characterization of Ti{sub 4}AlN{sub 3}
Bulk samples of Ti{sub 4}AlN{sub 3} were fabricated by reactive hot isostatic pressing (hipping) of TiH{sub 2}, AlN, and TiN powders at 1,275 C for 24 hours under 70 MPa. Further annealing at 1,325 C for 168 hours under Ar resulted in dense, predominantly single-phase samples, with <1 vol pct of TiN as a secondary phase. This ternary nitride, with a grain size of {approx}20 {micro}m on average, is relatively soft (Vickers hardness 2.5 GPa), lightweight (4.6 g/cm{sup 3}), and machinable. Its Young's and shear moduli are 310 and 127 GPa, respectively. The compressive and flexural strengths at room temperature are 475 and 350 MPa, respectively. At 1000 C, the deformation is plastic, with a maximum compressive stress of {approx}450 MPa. Ti{sub 4}AlN{sub 3} thermal shocks gradually, whereby the largest strength loss (50 pct) is seen at a {Delta}T of 1,000 C. Further increases in quench temperature, however, increase the retained strength before it ultimately decreases once again. This material is also damage tolerant; a 100 N-load diamond indentation, which produced an {approx}0.4 mm defect, reduces the flexural strength by only {approx}12 pct. The thermal-expansion coefficient in the 25 C to 1,100 C temperature range is 9.7 {+-} 0.2 x 10{sup {minus}6} C{sup {minus}1}. The room-temperature electrical conductivity is 0.5 x 10{sup 6} ({Omega}{center{underscore}dot}m){sup {minus}1}. The resistivity increases linearly with increasing temperature. Ti{sub 4}AlN{sub 3} is stable up to 1,500 C in Ar, but decomposes in air to form TiN at {approx}1,400 C.
- Research Organization:
- Drexel Univ., Philadelphia, PA (US)
- OSTI ID:
- 20015610
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 31, Issue 2; Other Information: PBD: Feb 2000; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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