Micromechanisms of monotonic and cyclic subcritical crack growth in advanced high-melting-point low-ductility intermetallics. Annual report No. 1, 15 Apr 90-14 Apr 91

Technical Report · Wed May 01 04:00:00 EDT 1991

OSTI ID:5164903

Rao, K T; Murugesh, L; DeJonghe, L C

The next generation of high-performance jet engines will require markedly stiffer materials, operating at higher stress levels and capable of withstanding temperatures of up to 1650 C. Prime candidates for such applications include ordered intermetallics, ceramics and composites based on metal, intermetallic and ceramic or carbon matrices, all of which are currently of limited use due to their low ductility and fracture properties. Moreover, there is a lack of fundamental understanding on the micromechanisms influencing crack growth in these materials, particularly intermetallics. Accordingly, the present study is aimed at exploring the potential of intermetallic alloys and their composites as advanced structural materials by identifying the critical factors influencing the crack-propagation resistance under monotonic and cyclic loads. Attention is focused on the Nb{sub 3}Al and TiAl intermetallic systems. In both cases, the principal mechanism of toughening is to impede crack advance from crack bridging by ductile second phase particles. Reactive sintering and vacuum hot pressing techniques are successful is processing Nb{sub 3}Al intermetallics and duplex Nb/Nb{sub 3}Al microstructure with a stringy niobium phase can be achieved through thermal treatments. Characterization of mechanical properties will commence in the second year.

• Research Organization: California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering
• OSTI ID: 5164903
• Report Number(s): AD-A-238151/5/XAB; CNN: AFOSR-90-0167
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
AIRCRAFT
ALLOYS
ALUMINIUM ALLOYS
BRIDGES
CERAMICS
COMPOSITE MATERIALS
CRACK PROPAGATION
CRACKS
CRYSTAL STRUCTURE
DUCTILITY
ELEMENTS
FABRICATION
FRACTURE MECHANICS
FRACTURE PROPERTIES
HEAT TREATMENTS
HOT PRESSING
INTERMETALLIC COMPOUNDS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
MECHANICAL STRUCTURES
MECHANICS
METALS
MICROSTRUCTURE
NIOBIUM ALLOYS
PARTICLES
PRESSING
SINTERING
STRESSES
TENSILE PROPERTIES
TITANIUM ALLOYS