Mechanical properties of Ir-Nb alloys containing Ni and Al |
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Authors: | X H Yu Y Yamabe-Mitarai S Nakazawa Y Ro H Harada |
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Affiliation: | (1) the Department of Mechanical and Industrial Engineering, University of Manitoba, R3T 5V6 Winnipeg, MB, Canada;(2) the High-Temperature Materials 21 Project, National Research Institute for Metals, 305-0047 Ibaraki, Japan |
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Abstract: | Two alloys made by adding 5 or 10 at. pct, respectively, of Ni-18.9 at. pct Al to an Ir-15 at. pct Nb alloy were investigated.
The microstructure and compressive strength at temperatures between room temperature and 1800 °C were investigated to evaluate
the potential of these alloys for ultra-high-temperature use. Their microstructural evolution indicated that the two alloys
formed fcc and L12-Ir3Nb two-phase structures. The fcc and L12 two-phase structures were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The
0.2 pct flow stresses were above 1000 MPa at temperatures up to 1200 °C, about 150 MPa at 1500 °C, and over 100 MPa at 1800
°C. The strength of the quaternary Ir-base alloys at 1200 °C was even higher than that of Ir-base binary and ternary alloys.
And the strength of quaternary Ir-Nb-Ni-Al was equivalent to that of the Ir-15 at. pct Nb binary alloy at 1800 °C. The compressive
ductility of quaternary (around 20 pct) was improved drastically compared with that of the Ir-base binary alloy (lower than
10 pct) and the ternary Ir-base alloys (about 11 pct). An excellent balance of high-temperature strength and ductility was
obtained in the alloy with 10 at. pct Ni-18.9 at. pct Al. The effect of Ni and Al on the strength of the Ir-Nb binary alloy
is discussed. |
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