Structure and properties of a β solution treated,quenched, and aged si-bearing near-α titanium alloy |
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Authors: | G Sridhar D S Sarma |
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Affiliation: | (1) Department of Metallurgical Engineering, Banaras Hindu University, 221 005 Varanasi, India;(2) Present address: National Metallurgical Laboratory, 831 007 Jamshepur, India;(3) Department of Metallurgical Engineering, Banaras Hindu University, 221 005 Varanasi, India |
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Abstract: | The microstructure, tensile properties, and fractographic features of a near-α titanium alloy, IMI 829(Ti-6.1 wt pct Al-3.2
wt pct Zr-3.3 wt pct Sn-1 wt pct Nb-05 wt pct Mo-0.32 wt pct Si) have been studied after aging over a temperature range of
550°C to 950°C for 24 hours following solution treatment in the β phase field at 1050°C and water quenching. Transmission
electron microscopy studies revealed that aging at 625°C and above produced discrete silicides at α′ interplatelet boundaries.
However, aging at 900°C and above has also resulted in the precipitation of β phase along the lath boundaries of martensite.
The silicides have been found to have a hexagonal structure withc=0.36 nm anda=0.70 nm (designated as S2 by earlier workers). There is a significant improvement in yield and ultimate tensile strength after aging at 625°C, but
there is less improvement at higher aging temperatures. The tensile ductility is found to be drastically reduced. While the
fracture surface of the unaged specimen shows elongated dimples, the aged samples show a mixed mode of fracture, consisting
of facets, featureless parallel bands, and extremely fine dimples. |
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