Small amount TiB₂addition into B₄C through sputter deposition and hot pressing

Abstract

Small amount of TiB2 (<5 wt%) was added into B4C through a novel method that combines the use of sputter deposition and hot pressing. Sputter deposition provided more uniform dispersion of TiB2 grains with smaller grain sizes as compared to the conventional particulate mixing. Small amount TiB2 addition demonstrated to be an effective way for improving the fracture behavior and toughness of B4C while not sacrificing its outstanding lightweight property to a large extent: 2.3 wt% TiB2 addition brought 15% improvement in indentation fracture toughness while resulting in less than 2% increase in density. The improvement can be attributed to the combination of crack impeding by TiB2 grains and crack deflection at the B4C–TiB2 interfaces. TiB2 also played as grain growth inhibitor resulting in a slight increase (2%) in Vickers hardness. Another intention of employing sputter deposition was to modify the grain boundary of B4C; however, neither formation of Ti‐containing phase nor Ti segregation has been observed at grain boundaries likely due to the poor wettability of B4C.

Addressing amorphization and transgranular fracture of B4C through Si doping and TiB2 microparticle reinforcing

“…18 growth. Similar results were observed in other systems, like SiC/TiB 2 (82) and B 4 C/TiB 2 (27).…”

“…(75,76) This can be attributed to the residual stress built by the lattice and thermal mismatches between B 4 C and TiB 2 phase. (12,74,77), which is estimated to be ~500 MPa (27,78). Taken together, the B 4 C-TiB 2 composite displays a mixture of transgranular and intergranular fracture modes.…”

“…More recently, sputter deposition of TiB 2 on B 4 C powders was utilized to hot press B 4 C-TiB 2 composites with a small amount of well-dispersed TiB 2 particulates. Indentation fracture toughness of B 4 C was improved by 15% with the addition of 2.3 wt.% TiB 2 , while its bulk density was only 2% higher than that of a monolithic B 4 C 27. Toreinforce B 4 C with TiB 2 , commercial powders of B 4 C (Grade HD20, H.C. Starck, d 50 = 0.7 μm) and TiB 2 (Grade F, H.C. Starck, d 50 = 2.5 μm) were used.…”

“…The reinforcement of transition-metal diborides has shown to hinder the propagation of crack and alter its traveling mode in boron carbide. 27,28 On the other hand, atomic doping has demonstrated to be a viable method to suppress amorphization. 23,[29][30][31] Therefore, a solution comprised of microstructural reinforcement and atomic doping could address both failure mechanisms of boron carbide simultaneously.…”

“…One possible way to alter the fracture behavior of boron carbide is to form a microstructural‐level composite with a secondary phase reinforcement. The reinforcement of transition‐metal diborides has shown to hinder the propagation of crack and alter its traveling mode in boron carbide 27,28 . On the other hand, atomic doping has demonstrated to be a viable method to suppress amorphization 23,29–31 .…”