Effects of degree of deformation on the microstructure, mechanical properties and texture of hybrid-reinforced titanium matrix composites

Titanium matrix composites reinforced by TiB whiskers and La2O3 particles are synthesized in a consumable vacuum arc remelting furnace by an in situ technique based on the reaction between Ti, LaB6 and oxygen in the raw material. The titanium matrix composites are hot rolled with degrees of deformation of 60%, 80%, 90% and 95%. The effects of the hot rolling degree of deformation on the mechanical properties of the composites are investigated by experiment and modeling. In particular, the variation in the inclination of the TiB whiskers during rolling is quantified in the model. The results show that, with increasing degree of deformation, the mechanical properties of composites are improved. Modeling of the mechanical properties reveals that grain refinement and TiB whisker rotation during rolling contribute to the improvement in the yield strength of the titanium matrix composites. Electron backscatter diffraction and transmission electron microscopy observations are used to study the texture of the composites. It is found that the orientation relationships between Ti matrix and TiB whiskers are [11-20](Ti) parallel to [0 1 0](TiB), (0 0 0 1)(Ti) parallel to (0 0 1)(TiB) and (1-1 0 0)(Ti) parallel to(1 0 0)(TiB). TiB whiskers rotate in the rolling direction (RD) with increasing degree of deformation, which results in a higher intensity [11-20](Ti) parallel to RD fiber due to the special orientation relationship between TiB and the Ti matrix. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.