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B4C-TiB2-W2B5 Composites


Sintering temperature, density, hardness (Vickers) flexural strength fracture toughness of material, C / / GPaiMPa, IPa · mB. C (HP) 2000-220093-9535-43300-5001.23.6B {C-Tz-w2B5 (HP) 1820> 973883045B {C-Tz-W2B5 (HIP) l700> 9938l0305.6 Figure 3, the sintering temperature on the fracture toughness sintered density of Figure 4,[link widoczny dla zalogowanych], the time between grinding and Zhang note in Table 1. After 2h milled, (WC + TiC + Co) of the mixed volume is close to 5O. A far cry from the original ingredients. Table 2 shows, when the sintering temperature is 1600 \The final sample for the C-TiB basic organization of a WB. There is also a small amount of U and U-phase (the specific composition and structure of unknown) This conclusion results from the density measurement (see Figure 4) can be further instructions. Figure 1 shows, the addition of elements si BC significantly improved the sintered density, and the effect of 7.5wtsi best. This and the expected results. Figure 5 is the present results obtained by thermodynamic calculations of the B-C-Si isothermal section of phase diagram. That down there in the 1800 ~ C Bc (s) and Si (L) two-phase region. Figure winning three out of the original components of the experiment, one of which is at the point with 7.5wtSi BC (s) + Si (L) two-phase region. Therefore,[link widoczny dla zalogowanych], we can consider that the experiment of No. 15 Air 764 sintered density increased significantly and the liquid is directly related to the process of firing drill. Strength increase is mainly due to grain refinement ( 97%). This can be famous Kundsen full description of the equation], that is, a aodexp 'here, o'b as bending strength, d is grain size, P is porosity,[link widoczny dla zalogowanych], n, and for the constant and the quantitative relation between P 0 a 890exp. r = 0.92 (HP) significantly improved fracture toughness of TiB and wB high coefficient of thermal expansion of about 6.5 ~ 9.5 × 106/X2, while the matrix Bc low coefficient of thermal expansion of about 4.5 ~ 5.5 × lol / ℃. Difference between 2 ~ 4 × 101 / ℃. Cooled down from a high temperature difference that must be produced when the thermal expansion mismatch Figure 5B-C-si isothermal sections (about 1850C) stress, under Selsing and others work, estimated that stress is a 1.7MPa △ 1.5 T / ~ C, for example, cooling from 1500 ℃ to room temperature, it will in the TiB. (W. B) phase produces about 2.25 ~ 2.55GPa around the radial tensile stress. In such a large internal stress, the occurrence of crack branching and micro-crack process is inevitable. More importantly,[link widoczny dla zalogowanych], the TiB. (W: B) phase and Bc bonding between the matrix is weak, coupled with the additional role of the radial tensile stress, the crack propagation process along the interface tends to that crack deflection effects. Tortuous route of crack propagation is the fracture toughness significantly improve the main reason. 3 Conclusions (1) through the initial powder composition and reaction sintering process control, get a wB = Bc-Ti composites. The material shows high strength and fracture toughness (1030MPa, 5.6MPa · / m), which is of great engineering significance. (2) the addition of elements of sl (about 7.5wt% Si) can significantly improve the sintering behavior and improve the sintered density,[link widoczny dla zalogowanych], and to the sintering temperature down to 1700 ℃ ~ 1800 ℃. (3) the hot reaction produced by burning high drilling density and fine grain structure is the root cause of strength, while a significant increase in fracture toughness was mainly due to TiB (wB) and B. c coefficient of thermal expansion mismatch between the enormous stress (1.5 ~ 1.7MPa △ T / C) and micro-cracks produced and crack deflection.