Combustion synthesis of cubic Al sub 3 Ti alloys

Journal Article · Thu Oct 01 04:00:00 EDT 1992 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1992.2733· OSTI ID:6979663

Wright, R N; Rabin, B H; McFerran, W H ^[1]

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1. Idaho National Engineering Laboratory, EG G Idaho, Inc., Idaho Falls, Idaho 83415-2218 (United States)

Combustion synthesis of elemental powder compacts has been used to produce alloys with compositions corresponding to Al{sub 3}Ti, Al{sub 73}Ti{sub 24}Cr{sub 3}, and Al{sub 67}Ti{sub 25}Cr{sub 8}. The binary composition exhibits a strong exothermic reaction at {similar to}665 {degree}C, resulting in formation of single phase Al{sub 3} Ti with the tetragonal D0{sub 22} structure. The heat of formation of the compound at 298 K, {Delta}{ital H}{sub {ital f}}{sup 0}(298), was estimated from peak reaction temperature measurements to be {minus}35.0 kJ mol{sup {minus}1}. Additions of Cr lowered the reaction initiation temperature and resulted in the formation of intermediate products attributed to Al--Cr reactions. The D0{sub 22} structure remained the primary reaction product in Cr-containing alloys. The Cr particles did not completely dissolve during initial reaction; an additional heat treatment at 1200 {degree}C or above was required to homogenize the material, resulting in partial or complete transformation of the D0{sub 22} structure to the cubic L1{sub 2} structure, depending upon Cr content. Homogenization at 1250 {degree}C for 4 h produced material consisting approximately of a 50-50% mixture of the D0{sub 22} and L1{sub 2} structures for Al{sub 73}Ti{sub 24}Cr{sub 3}, and 100% L1{sub 2} for Al{sub 67}Ti{sub 25}Cr{sub 8}. In all cases, reaction at ambient pressure was accompanied by swelling, resulting in final densities less than 60% of theoretical. Application of external pressure, either during or subsequent to combustion synthesis, produced near theoretical density materials exhibiting a homogeneous and equiaxed microstructure.

• DOE Contract Number: AC07-76ID01570
• OSTI ID: 6979663
• Journal Information: Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 7:10; ISSN JMREE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
ALLOYS
ALUMINIUM ALLOYS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
COMBUSTION
ENTHALPY
FORMATION HEAT
OXIDATION
PHYSICAL PROPERTIES
POWDERS
REACTION HEAT
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
THERMOCHEMICAL PROCESSES
THERMODYNAMIC PROPERTIES
TITANIUM ALLOYS