Effects of microstructure on creep of Ti-24Al-11Nb polycrystals

Thesis/Dissertation · Mon Dec 31 23:00:00 EST 1990

OSTI ID:5404598

Albert, D E

The purpose was to determine the steady-state creep rate (CRSS) of various microstructures of Ti-24Al-11Nb (a/o). This alloy is a two-phase ({beta} + {alpha}{sub 2}) Ti{sub 3}Al-based aluminide with niobium added to stabilize {beta}. The microstructure of the heat-treated alloy is lath {alpha}{sub 2} surrounded by a thin film of {beta} arranged in a basketweave morphology, while the as-received microstructure consists of equiaxed {alpha}{sub 2} plus a small amount of {beta}. SSCR vs. stress and vs. temperature curves were determined to find Q{sub a}, apparent creep activation energy, and n, power law stress exponent. At low stresses, Q{sub a}s determined for all microstructures were found to be between 106 kJ/mol and 145 kJ/mol, which agrees fairly well with the value of 121 kJ/mol previously obtained for grain boundary diffusional creep in titanium at low stresses. Mechanical-test results show that microstructures with a coarse {alpha}{sub 2} lath size in general display improved creep resistance over fine-lathed structures. Specimens with an equiaxed {alpha}{sub 2} phase microstructure exhibit much greater creep rates at all stresses and temperatures.

• Research Organization: Carnegie-Mellon Univ., Pittsburgh, PA (United States)
• OSTI ID: 5404598
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
CREEP
CRYSTAL STRUCTURE
ENGINES
GAS TURBINE ENGINES
HEAT ENGINES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INTERNAL COMBUSTION ENGINES
MATERIALS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
MICROSTRUCTURE
NIOBIUM ALLOYS
TITANIUM ALLOYS
TITANIUM BASE ALLOYS