Hot Flow Behavior of B-Added Steel

Materials Science and Engineering A 480 (2008) 49–55

Hot flow behavior of boron microalloyed steels

E. L´ pez-Chipres a , I. Mej´a a,∗ , C. Maldonado a , o ı a , M. El-Wahabi b , J.M. Cabrera b,c A. Bedolla-Jacuinde

Instituto de Investigaciones Metal´ rgicas, Universidad Michoacana de San Nicol´ s de Hidalgo. u a Edificio “U”, Ciudad Universitaria, 58066 Morelia, Michoac´ n, Mexico a b Departament de Ci` ncia dels Materials i Enginyeria Metall´ rgica, ETSEIB, Universitat Polit` cnica de Catalunya. e u e Av. Diagonal 647, 08028 Barcelona, Spain c CTM Centre Tecnol` gic. Av. de las Bases de Manresa, 1, de Manresa, 08240 Manresa, Spain o Received 5 April 2007; received in revised form 23 June 2007; accepted 25 June 2007

a

Abstract This research work studies the effect of boron contents on the hot flow behavior of boron microalloyed steels. For this purpose, uniaxial hotcompression tests were carried out in a low carbon steel microalloyed with four different amounts of boron over a wide range of temperatures (950, 1000, 1050 and 1100 ◦ C) and constant true strain rates (10−3 , 10−2 and 10−1 s−1 ). Experimental results revealed that both peak stress and peak strain tend to decrease as boron content increases, which indicates that boron additions have a solid solution softening effect. Likewise, the flow curves show a delaying effect on the kinetics of dynamic recrystallization (DRX) when increasing boron content. Deformed microstructures show a finer austenitic grain size in the steel with higher boron content (grain refinement effect). Results are discussed in terms of boron segregation towards austenitic grain boundaries during plastic deformation, which increases the movement of dislocations, enhances the grain boundary cohesion and modificates the grain boundary structure. © 2007 Elsevier B.V. All rights reserved.

Keywords: Hot flow behavior; Boron microalloyed steel; Dynamic recrystallization; Boron segregation; Solid solution softening; Austenitic grain size...