Spark Sintering of TiB₂ Reinforced Fe Matrix Composites with Both High Thermal Conductivity and Hardness, and Their Microstructural Characterizations

Abstract

TiB 2 reinforced Fe matrix composites were investigated for their potential as a new generation of hot work tools which are mainly characterized by high thermal conductivity and high hardness in comparison with conventional materials. In this work, Fe30 vol%TiB 2 composites were sintered at 1373 K for different holding times (0, 0.3, 0.6, 1.8 and 3.6 ks). Apart from Fe and TiB 2 , newly formed phases of Fe 2 B and TiC were found in all sintered compacts. A good Fe/TiB 2 interfacial cohesion was confirmed at atomic level at 0 ks, which was due to the occurrence of the special orientation relationship between {110} planes of Fe and f10 10g planes of TiB 2. The observation of dislocations in TiB 2 particles, attributed to the activation of slip systems, showed the plastic deformation ability of TiB 2 at high temperature. The reaction between Fe and TiB 2 was due to TiB 2 dissolution in Fe at 1373 K and different diffusion depth of B and Ti atoms in Fe. Consequently, B directly reacted with Fe, since the solubility of B atoms was low in both ¡-Fe and £-Fe. TiC probably precipitated from FeTiC solid solution along Fe grain boundaries in the cooling stage after sparking sintering, leading to a layer of Fe wrapping around TiB 2. Among all the compacts, the one sintered at 1373 K for 0.6 ks displayed the excellent properties which were comparable in Vickers hardness and 133% higher in thermal conductivity, compared with that of SKD61 as the commonly used practical material. This work provides a new perspective to fabricate a future generation of hot work tools.