Synthesis of 30 vol%TiB₂ Containing Fe–5Ti Matrix Composites with High Thermal Conductivity and Hardness

抄録

TiB₂ doped Fe system alloys composites as a new generation of novel materials in sustainable society show the great potential in hot work tool steels usage. Compared with SKD61, the new generation materials are focused on improving both thermal conductivity and hardness. For the suppression of TiB₂ decomposition and Fe₂B formation, monophase BCC structured Fe–5Ti alloy powders were fabricated by mechanical allying method. The TiB₂ addition with 30 vol% was selected for the control of hardness. The compacts sintered at 1323 and 1373 K for 0.6 ks consisted of α-Fe and TiB₂ with almost 30 vol%, which meant no decomposition of TiB₂ occurred during sintering. The result agreed with the achievement of thermal stability of TiB₂ in Fe–5Ti during spark sintering synthesis. The thermal conductivity and Vickers hardness of compacts sintered at 1323 and 1373 K for 0.6 ks were 48.0 W/(m·K), 684.7 HV and 53.5 W/(m·K), 717.5 HV, respectively, which were 2.0, 1.3 and 2.2, 1.4 folds than those (24.0 W/(m·K), 516.0 HV) of SKD61. In addition, the compression strength of two compacts sintered at 1323 and 1373 K were measured to be 1698 and 2591 MPa, respectively. The compact sintered at higher temperature showed better mechanical properties and higher thermal conductivity due to the improvement of densification and interface bonding between Fe–5Ti and TiB₂ as proved by the fracture modes in compression tests and the crack propagations in hardness tests. Hence, this work provides a new method for fabricating Fe₂B free Fe–TiB₂ composites by powder metallurgy with both improvement of thermal conductivity and hardness in the usage of hot work tool steels.

Fig. 5 SEM images of (Fe–5Ti)–30 vol%TiB₂ compacts sintered at (a) 1323 and (b) 1373 K for 0.6 ks; pores are indicated in the upper-left insets corresponding to the marked areas by white boxes in (a), (b).