Protrusions formed during primary recrystallization of cross-rolled coarsegrained niobium

D.R. ALMEIDA; H. R.Z SANDIM; M. AVALOS; T. BREKAILO; R. BOLMARO

INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HARD MATERIALS

Elsevier

Año: 2019 vol. 85 p. 105080 - 105092

0958-0611

The growth of recrystallization nuclei towards the deformed matrix generally does not proceed isotropically.Local disturbances in the migration along grain boundaries lead to the formation of protrusions. This importantaspect in recrystallization is rarely explored in the literature, especially in the sense of understanding whichmicrostructural mechanisms explain its formation. The aim of this work is to study the formation of protrusionsduring the recrystallization of a niobium oligocrystal. A coarse-grained niobium plate was cut out from thelongitudinal section of an electron-beam cast ingot. Five coarse grains (A, B, C, D and E) were randomly selectedfor this study to evaluate likely orientation effects on protrusion formation. The plate was cold rolled withseveral passes up to 50% thickness reduction. The sheet was then cut into two parts. The former was straightrolled until 70% thickness reduction while the latter was rotated 90° around the normal direction with respect tothe initial rolling direction. Important orientation and rolling mode effects were noticed regarding their recrystallization behavior. Protrusions were more abundant in the cross-rolled specimens. It was not possible toidentify and associate significant differences regarding either CSL-type special boundaries or highly-misorientedboundaries ahead of the boundaries showing protrusions.