Creep deformation and fracture of a two-phase TiAl alloy

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Scripta Metallurgica; (United States)

DOI:https://doi.org/10.1016/0956-716X(91)90325-U· OSTI ID:5528434

Huang, J S ^[1]; Kim, Y W ^[2]

---

1. Lawrence Livermore National Lab., CA (United States). Chemistry and Materials Science Dept.
2. Metcut-Materials Research Group, Wright-Patterson, AFB, OH (US)

This paper reports that gamma TiAl (L1{sub 0} structure), which is structurally stable up to about 1460{degrees}C and exhibits good specific strength, modulus, and oxidation resistance at high temperature, is a potential candidate structural material for high temperature service such as required for heat engines. Due to it inherent brittleness at ambient temperature, extensive efforts have been made in recent years to develop more ductile alloys. This was primarily done through additions of Cr, V, Mn, Nb, and Ta, and manipulation of microstructure for two-phase (gamma + alpha-2) alloys based on Ti. Depending upon heat treatments, these alloys exhibit four different types of microstructure: fully-lamellar, nearly-lamellar, duplex, and nearly-gamma. Fully-lamellar structures consisting of large grains with alternating gamma and alpha-2 platelets are know to yield high toughness and creep resistance, and duplex microstructures result in the highest ductility at room temperature. A number of researchers have studied the deformation behavior of single-phase TiAl alloys, while there are only limited number of reports on the deformation behavior of two-phase alloys. The results show that in single phase (gamma) Ti-(52-54) at.% Al binaries, the slip systems are {l brace}111{r brace} planes and dislocation of a/2 {l angle}110{r angle}, a {l angle}101{r angle} and a/2 {l angle}112{r angle} types are present. The a{l angle}101{r angle} and a/2 {l angle}112{r angle} dislocations are superdislocations, which were found to undergo complex dissociation reactions, creating sessile faulted dipoles and contributing to the brittleness of TiAl alloys. For two-phase alloys, only the easy-slip type unit dislocation a/2 {l angle}110{r angle} and {l brace}111{r brace} twins were present after tensile deformation at room temperature.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5528434
• Journal Information: Scripta Metallurgica; (United States), Vol. 25:8; ISSN 0036-9748
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CORROSION RESISTANCE
CREEP
FRACTURE MECHANICS
PHASE STABILITY
YOUNG MODULUS
OXYGEN
DIFFUSION
TITANIUM ALLOYS
CRACK PROPAGATION
DEFORMATION
EMBRITTLEMENT
GRAIN BOUNDARIES
OXIDATION
SLIP FLOW
TEMPERATURE EFFECTS
THERMODYNAMIC PROPERTIES
ALLOYS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
ELEMENTS
FLUID FLOW
GAS FLOW
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
NONMETALS
PHYSICAL PROPERTIES
STABILITY
360103* - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies
360105 - Metals & Alloys- Corrosion & Erosion
360104 - Metals & Alloys- Physical Properties