Effect of Ti/Al ratio and Cr, Nb, and Hf additions on materials factors and mechanical properties in TiAl

Journal Article · Thu Dec 31 23:00:00 EST 1992 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02669611· OSTI ID:6353372

Kawabata, T ^[1]; Tamura, T ^[2]; Izumi, O ^[3]

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1. Atom Material Research Lab., Sendai (Japan)
2. Sony Corp., Ltd., Tagajo (Japan)
3. Tohoku Univ., Sendai (Japan)

The effect of the Ti/Al ratio and Cr, Nb, and Hf additions on material factors, such as the grain size, second phase, lattice parameters and the axial ratio, and on mechanical properties in TiAl-base alloys has been studied. The grain size was decreased by the deviation from the stoichiometric composition to the Ti-rich side and the addition of the third elements. The lattice parameters, a and c, and the axial ratio, c/a, of the binary alloys varied linearly, with decreasing Al content even in the dual-phase region. In the Cr added alloys, the decrease of volume of a unit cell, due to the substitution of Cr atoms for Ti and Al atoms, was larger than that expected from the difference of atom sizes. The Nb addition increased the volume. The Hf addition caused a larger increase of volume of a unit cell than that expected. The authors suggested that the Cr addition increases and the Nb and Hf additions decrease the bond strength in TiAl. The deviation from stoichiometry and the addition of third elements caused an increase of work-hardening rate. The alloys with Ti-rich composition have superior mechanical properties compared to those of alloys with Al-rich composition. The Cr addition resulted in high solution hardening, and the Ti-47Al-3Cr (in atomic percent) alloys had the highest fracture strain of 2.7 pct in all alloys tested. The Nb addition resulted in poor ductility in both Ti- and Al-rich alloys. The Hf additions to the Ti-rich composition caused better mechanical properties than those of Al-rich alloys. This trend was also similar to the Nb-added alloys. In the Hf-added alloys, the Ti-49Al-2Hf alloy has rather high ductility of about 2.15 pct. The effect of structural parameters on mechanical properties was discussed. The smaller grain size and the smaller axial ratio tended to result in larger ductility. The increase of the bond strength might improve ductility.

• OSTI ID: 6353372
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 24:1; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
CHROMIUM
CHROMIUM ADDITIONS
CHROMIUM ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DUCTILITY
ELEMENTS
FRACTURE PROPERTIES
GRAIN SIZE
HAFNIUM
HAFNIUM ADDITIONS
HAFNIUM ALLOYS
HARDENING
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALS
MICROSTRUCTURE
NIOBIUM
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
PHASE STUDIES
SIZE
STOICHIOMETRY
TENSILE PROPERTIES
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
TRANSITION ELEMENTS