Pd. Nicolaou et Sl. Semiatin, AN INVESTIGATION OF THE EFFECT OF TEXTURE ON THE HIGH-TEMPERATURE FLOW BEHAVIOR OF AN ORTHORHOMBIC TITANIUM ALUMINIDE ALLOY, Metallurgical and materials transactions. A, Physical metallurgy andmaterials science, 28(3A), 1997, pp. 885-893
The effect of mechanical and crystallographic texture on the flow prop
erties of a Ti-21A1-22Nb (at. pct) sheet alloy was determined by condu
cting uniaxial tension and plane-strain compression tests at temperatu
res between 900 degrees C and 1060 degrees C and strain rates between
10(-4) and 10(-2) s(-1). Despite, the presence of noticeable initial t
exture, all of the mechanical properties for a given test temperature
and strain rate (i.e., peak stress, total elongation to failure, strai
n-rate sensitivity, and normal plastic anisotropy) were essentially id
entical irrespective of test direction relative to the rolling directi
on of the sheet. The absence of an effect of mechanical texture on pro
perties such as ductility was explained by the following: (1) the init
ially elongated second-phase particles break up during tension tests p
arallel to the rolling direction of the sheet, thereby producing a glo
bular morphology similar to that noted in samples taken transverse to
the rolling direction; and (2) failure was flow localization, rather t
han fracture, controlled. Similarly, the absence of an effect of mecha
nical texture on strain-rate: sensitivity (m values), normal plastic a
nisotropy (r values), and the ratio of the plane strain to uniaxial fl
ow stresses was rationalized on the basis of the dominance of matrix (
dislocation) slip processes within the ordered beta phase (B2) as oppo
sed to grain boundary sliding. Aggregate theory predictions supported
this conclusion inasmuch as the crystallographic texture components de
termined for the B2 phase ((001) [100] and (<(1)over bar 12>) [110]) w
ould each produce identical r values and uniaxial and plane-strain flo
w stresses in the rolling and transverse directions.