Phase transitions in reactive formation of Ti{sub 5}Si{sub 3}/TiAl in situ composites

Journal Article · Wed Mar 01 04:00:00 EST 2000 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-000-0018-1· OSTI ID:20023150

Du, Y J; Rao, K P; Chung, J C.Y.; Han, X D

A new method is developed for preparing Ti{sub 5}Si{sub 3}/TiAl in situ composites by incorporating metastable phases (called metastable precursors) into TiAl (a mixture of elemental Ti and Al) matrix powders. Metastable precursors with a starting composition of Ti-14Al-2lSi are prepared by mechanical alloying (MA). They have been proven through X-ray diffraction (XRD) analysis and transmission electron microscope (TEM) observations to be mainly consisting of mixtures of nanostructured solid solution and milling-formed TiAl compound. Particularly, phase reactions and transitions in the precursors and the composites during heating have been investigated in detail by using diffraction thermal analysis (DTA) in conjunction with XRD. It has been found that Ti{sub 5}Si{sub 3} is in situ formed through a phase transition chain, TiSi{sub 2} {r_arrow} Ti{sub 5}Si{sub 4} {r_arrow} Ti{sub 5}Si{sub 3}. When the composite powder (precursor, Ti and Al) is heated, a combustion reaction first occurs in the matrix, which results in the formation of TiAl{sub 3} and/or TiAl followed by the completion of the previously mentioned silicide transitions in a very short time. Scanning electron microscopy (SEM) observations indicated the locations of reinforcements in the reaction-formed composite, and TEM observation provided some details of the structures for the reinforcements and their neighborhood. This method is intriguing because a designed phase hierarchy is possible.

• Research Organization: City Univ. of Hong Kong, Kowloon (HK)
• OSTI ID: 20023150
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 3 Vol. 31; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
COMPOSITE MATERIALS
ELECTRON MICROSCOPY
FABRICATION
INTERMETALLIC COMPOUNDS
PHASE STUDIES
POWDERS
TITANIUM ALLOYS
TITANIUM SILICIDES
X-RAY DIFFRACTION