Ct. Forwood et Ma. Gibson, Slip transfer of deformation twins in duplex gamma-based Ti-Al alloys. Part II. Transfer across gamma-alpha(2) interfaces, PHIL MAG A, 80(12), 2000, pp. 2785-2811
The interactions of 1/6[112]{111}gamma slip dislocations in deformation twi
ns with {111}(gamma)-(0001)alpha (2) interphase interfaces, intersecting al
ong both [101](gamma) (30 degrees -type) and [110]gamma (edge-type) directi
ons. in duplex Ti-Al alloys after room-temperature deformation in tension,
have been investigated by transmission electron microscopy. The dislocation
reactions involved in each of these types of interaction have been fully i
dentified by image matching between experimental and computed images. Slip
transfer of 30 degrees -type 1/6[112]{111}, twinning dislocations across th
e gamma-alpha (2) interface into 1/3[1120]{1100}(alpha2) slip dislocations
has been confirmed and completely characterized. In addition to this: prima
ry slip system a new secondary slip system of 1/3[1(1) over bar 20](3(3) ov
er bar 01}alpha (2) is activated within the alpha (2) phase under condition
s of high levels of plastic strain. This new slip system has also been obse
rved to be the favoured route for slip transfer of incoming 30 degrees -typ
e 1/6[112]{111}(gamma) twinning dislocations when the plane of the gamma-al
pha (2) interface deviates significantly from {111}(gamma)-(0001)alpha (2)
and the line of intersection is no longer close to [101](gamma). For the in
teraction involving edge-type 1/6[112]{111}(gamma) twinning dislocations wi
th {111}(gamma)-(0001)(alpha2) gamma-alpha (2) interfaces, no significant t
ransfer of dislocations into the alpha (2) phase was observed. Instead, str
ess relief of the incoming twinning dislocation pile-up at the yat interfac
e occurs via 1/2[110]{001}(gamma) slip dislocations 'reflecting' back into
the gamma phase coupled with the generation of a new twinned gamma grain at
the gamma-alpha (2) interface. No dislocation reactions involving c-compon
ent dislocations in the alpha (2) phase were observed for any of the intera
ctions investigated.