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Structure and Microstructure of Al2Ti Intermetallic Alloy

Published online by Cambridge University Press:  01 January 1992

John E. Benci,
John C. Ma and
Thomas P. Feist
John E. Benci
Affiliation:
Department of Materials Science and Engineering, Wayne State University, Detroit, MI 48202.
John C. Ma
Affiliation:
Department of Materials Science and Engineering, Wayne State University, Detroit, MI 48202.
Thomas P. Feist
Affiliation:
Central Research and Development, E.I. DuPont de Nemours & Company, Inc., Wilmington, DE 19880.
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Abstract

Alloys based on intermetallic compounds in the Ti-Al binary system have been extensively investigated as candidate light weight structural materials for elevated temperature applications. However, one compound in this system, Al2Ti, has been virtually ignored. Al2Ti, like Al3Ti, is expected to possess lower density and better oxidation resistance compared to Ti3Al and TiAl based alloys. Since the structure and stability of Al2Ti are poorly understood, this work was undertaken to determine the compound's equilibrium crystal structure and the microstructures in the as-cast, melt-spun, and annealed conditions. Powder X-ray diffraction shows that annealed melt-spun Al2Ti has the tetragonal Ga2Hf crystal structure containing 24 atoms per unit cell with a = 3.9705 Å, c = 24.322 Å and a calculated density of 3.530 g/cm3. Optical microscopy and scanning electron microscopy with energy dispersive spectroscopy were used to investigate the material's microstructures. Cast Al2Ti has a small volume fraction of TiAl second phase particles. Rapidly solidified and annealed Al2Ti is single phase. Powder processing (melt spinning and hot isostatic pressing) Al2Ti yields material with a finer microstructure, a higher hardness, and increased resistance to room temperature cracking than as-cast material. Additionally, microhardness results indicate that Al2Ti has an increased resistance to cracking at room temperature than identically processed Al3Ti with a similar hardness.

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References

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