Effects of rolling deformation on microstructure orientations and tensile properties of TiB/(TA15-Si) composites

Abstract

To explore the orientation evolution and interfacial characteristics under the β-phase region, rolling deformation with different reduction ratios of 40– 90% was carried out by hot-pressing sintering and multi-pass hot rolling on a series of TiB whiskers reinforced Ti-6.5Al-2Zr-1Mo-1 V-0.3Si (TiB/(TA15-Si)). As rolling deformation increased, the matrix exhibited slight refining and distortion within lamella α + β, and a stronger T-type α texture was gradually formed. A portion of Burgers Orientation Relation (BOR) between parent β and α phases gradually disappeared due to a decrease in rolling temperature and post deformation after phase transformation. Meanwhile, TiB rotated and presented an intenser orientation of {100} 〈010〉. Silicides heterogeneously precipitated along the α/β phase boundaries both near and away from TiB. Silicide/matrix remained fine interfaces owing to resolution and reprecipitation. Finally, the ultimate strengths at room temperature were monotonously improved with the increase of deformation due to strong work hardening. And an anisotropy of tensile properties was found under large deformation. The composite tensioned along the transverse direction (TD) can exhibit higher strength and lower ductility due to mutual competition of TD strengthening by T-type texture and RD strengthening by TiB distribution, especially at 600 °C. The fracture paths of as-rolled composites were discussed in detail. • Matrix gradually formed an intenser T-type α texture mainly inherited from β by BOR. • TiB can form an obvious orientation of {100}<010 > but have a minor proportion of OR. • Most silicide/matrix interfaces possessed orientation relations in the β-rolled composites. • The ultrahigh ultimate strength of 1505 MPa was obtained in the 90%-rolled composite. • Composites along TD exhibited higher strength and lower ductility especially at 600 °C.