TiB2含量对B4C-TiB2-Al复合材料组织与力学性能的影响

通过在B4C-TiB2预烧体中真空熔渗Al制备了B4C-TiB2-Al复合材料,研究了TiB2含量对复合材料显微组织和力学性能的影响.结果表明: B4C-TiB2-Al复合材料主要由B4C,TiB2,Al和Al3BC等相组成;随着TiB2含量的增加,复合材料的HRA硬度逐渐降低,抗弯强度逐渐增大,断裂韧性先增大后稍微降低,当TiB2含量为40%(质量分数)时,复合材料的气孔率、硬度HRA、抗弯强度和断裂韧性分别为1.32%,80.3,559.4 MPa和7.83 MPa·m1/2;延性Al的加入,裂纹的偏转和分叉、B4C和TiB2晶粒的细化以及B4C基体和TiB2晶粒热膨胀的不匹配,是造成材料断裂韧性提高的主要原因;随着Al渗入量的增加,复合材料断口中金属撕裂棱及韧窝的比例增加.

EFFECTS OF TiB2 CONTENT ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF B4C--TiB2--Al COMPOSITES

B4C-TiB2-Al composites were prepared by the method of infiltrating aluminum into B4C-TiB2 preform in vacuum. Investigations were carried out to analyze the effects of different content of TiB2 on the microstructure and properties of the composites. The results showed that B4C-TiB2-Al composite is mainly composed of B4C, TiB2, Al and Al3BC, and hardness decreases, bending strength increases and fracture toughness increases and then decreases lightly with the increase of TiB2 content,. Porosity, hardness, bending strength and fracture toughness of composite with 40 wt.% TiB2 are 1.32%, 80.3HRA, 559.4MPa and 7.83MPa•m1/2 respectively. It was found that the toughening mechanism of the composites is mainly that the addition of aluminum, the diminishment of B4C and TiB2 grain size, the crack deflection and divarication caused by the difference in thermal expansion coefficient between the matrix B4C and the particle TiB2. The ratio of metal tear ridges and dimples increase while the ratio of intergranular fractures and transgranular fractures decrease in the fracture surface with the increase of aluminum content.