Microstructural evolution and competitive reaction behavior of Ti-B4C system under solid-state sintering

Abstract

By using experimental investigations and theoretical calculations, microstructural evolution and competitive reaction behavior of Ti-B 4 C system under solid-state sintering is confirmed. Firstly, B 4 C decomposes into B and C atoms followed by diffusing into Ti side immediately, and TiB whiskers form in Ti matrix. Then, Ti atoms diffuse into B 4 C via vacancies left by the diffused B and C atoms, leading TiB 2 and carbon substance to form in B 4 C side. Subsequently, reaction product carbon diffuses into Ti side and concentration of C in Ti side increases accordingly, resulting in the formation of TiC particles in Ti matrix. With further processing of reaction, both amount and size of products increases gradually. When TiB 2 phases grow into a monolithic layer, diffusion behavior between Ti and B 4 C is inhabited, carbon presents to be a loose layer between un-reacted B 4 C and TiB 2, and the in situ reaction also stops finally.

Analysis of the Microstructure and Mechanical Properties of Titanium-Based Composites Reinforced by Secondary Phases and B4C Particles Produced via Direct Hot Pressing

“…However, TiC and TiB diffraction peaks appeared in the diffraction patterns of TMCs consolidated at 1000 °C as shown in Figure 2 b, while the XRD patterns of TiB 2 peaks were not detected since this phase transformation required longer [ 20 , 35 ]. This result aligns with previous work [ 36 ]. The intensities of the TiC and TiB diffraction peaks increased when the starting powder composition of the TMCs did not contain 20 vol % of Ti-Al, which indicated that the volume fraction of in-situ-formed TiC and TiB were affected by the addition of Ti-Al.…”

Performance of B4C/CeB6 composites fabricated via hot pressing under different processes

“…In recent years, researchers have made many attempts to solve the above problems. The most common method is to introduce the second phase into B 4 C ceramics, such as metallic phase (Al, Ti), oxide (Al 2 O 3 , ZrO 2 ), and boride (TiB 2 ), 6–10 to promote the densification and improve its comprehensive mechanical properties. Wang et al 11 .…”

“…In recent years, researchers have made many attempts to solve the above problems. The most common method is to introduce the second phase into B 4 C ceramics, such as metallic phase (Al, Ti), oxide (Al 2 O 3 , ZrO 2 ), and boride (TiB 2 ), [6][7][8][9][10] to promote the densification and improve its comprehensive mechanical properties. Wang et al 11 prepared B 4 C-GNPs composites with relative density, Vickers hardness, flexural strength, and fracture toughness of 99.12%, 32.80 GPa, 508 MPa, and 4.66 MPa⋅m 1/2 respectively under the condition of 1950 • C and 30 MPa pressure for 1 h. He et al 12 used B 4 C and Ti 3 SiC 2 as raw materials to prepare B 4 C-TiB 2 composites by reactive hot pressing at 2100 • C and 25 MPa pressure, of which the flexural strength, fracture toughness, and microhardness were 592 MPa, 7.01 MPa⋅m 1/2 , and 31.00 GPa, respectively.…”

Reaction Layer Analysis of In Situ Reinforced Titanium Composites: Influence of the Starting Material Composition on the Mechanical Properties

“…Therefore, the study of the reaction layer between the matrix and the particles is important in order to achieve a better understanding of Metals 2020, 10, 265; doi:10.3390/met10020265 www.mdpi.com/journal/metals Metals 2020, 10, 265 2 of 12 the cause that could promote or not these reactions and their products. While there is considerable literature on the grounds of strengthening and the reaction mechanisms [20,21], there are only a few studies where the reaction layer is analysed. It is also investigated how the presence of Ti x Al y as intermetallic in the titanium matrices could affect the final appearance of these secondary phases (TiB and TiC) [22][23][24]; however, the reaction layer in the presence of intermetallic, as well as its decomposition, has been little studied [25,26].…”