Microstructure and fracture behavior of Ti-44Al-xM derivatives
- Univ. of Birmingham (United Kingdom)
The microstructures of Ti-44Al alloys containing either 2 at.% Mo or 2 at.% Cr have been studied on as-cast, as HIPped and on heat-treated samples. Room temperature tensile tests have been carried out on the as-HIPped samples. It has been found that the microstructure of the as-cast sample of Ti-44Al-2Mo consists of large lamellar [alpha][sub 2]/[gamma] colonies and B2 and [gamma] blocks at subgrain boundaries, which divide the colonies into a number of small grains. The microstructure of the as-cast Ti-44Al-2Cr is fully lamellar [alpha][sub 2]/[gamma] with a small amount of segregation. The Ti-44Al-2Mo alloy shows a novel microstructure consisting of [gamma] grains, ([alpha][sub 2] + [gamma]) lamellae and B2 plates across the ([alpha][sub 2] + [gamma]) lamellae either after HIPping at 1,250 C or after annealing at 1,200 C, while large lamellar colonies were observed in the Ti-44Al-2Cr sample after the same treatments. Tortuous fracture surfaces with small cleavage facets and diverted crack paths have been observed by SEM in the Ti-44Al-2Mo samples. Delamination along [alpha][sub 2]/[gamma] interfaces and lamellar colony boundaries is the predominant failure mode of the Ti-44Al-2Cr sample. As HIPped samples of Ti-44Al-2Mo with a duplex microstructure modified by B2 have much higher room temperature tensile strengths and elongation than the as-HIPped samples of Ti-44Al-2Cr.
- OSTI ID:
- 6987526
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 42:9; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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