Structure and Properties of TiAl-Based Alloys Doped with Niobium and Chromium
2016
Quaternary as-cast Ti
96–x
Nb
2
Cr
2
Al
x
and Ti
93–x
Nb
5
Cr
2
Al
x
alloys, where x = 44, 46, 48, and 50, melted from pure components (~99.9 wt.%) in a laboratory arc furnace, were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and differential thermal analysis (DTA). Bending testing and fracture toughness measurements were performed at room temperature, and compression testing was carried out in a range from room temperature to 750°C. The alloys were found to consist mainly of a superfine lamellar structure formed during decomposition of hightemperature phases. In addition, the alloys with 50 at.% Al contain grains of the γ phase, and all others have precipitates of the cubic β/β
0
phase at boundaries of the high-temperature phases because of double enrichment of the last melt drops with Cr. The tests show that the Ti
96–x
Nb
2
Cr
2
Al
x
alloys with 46 and 48 at.% Al possess the most balanced properties.
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