TiB/Ti基复合材料的微观组织和力学性能

Microstructure and mechanical properties of TiB/Ti matrix composites

首先在纯Ti中添加MoB_(2)粉末,通过原位反应生成了TiB金属间化合物,随后采用非自耗电弧熔炼炉制备TiB/Ti基复合材料。采用X射线衍射(XRD)、光学显微镜(OM)、扫描电镜(SEM)、硬度测试和万能材料试验机等研究了TiB金属间化合物对TiB/Ti基复合材料的相结构、显微组织和力学性能的影响。结果表明:TiB/Ti基复合材料主要由α相、α′相、β相和TiB金属间化合物相组成;随着MoB_(2)添加量的增加,复合材料发生了Ti+MoB_(2)→α/α′(Ti)+β(Ti)+TiB的相变过程。原位反应生成的TiB增强相的相对含量随着MoB_(2)添加量的增加而增加。TiB增强相的形态均呈现出短棒状和纤维状。此外,随着MoB_(2)添加量的增加,TiB/Ti基复合材料的压缩屈服强度以及显微硬度大幅度提升,而其压缩应变则逐渐降低。当MoB_(2)添加量为7.5 mass%时,TiB/Ti基复合材料的压缩屈服强度和显微硬度分别为1095 MPa和397 HV0.2,而最大压缩强度和压缩应变则分别为1337 MPa和13.0%。TiB/Ti基复合材料的加工硬化指数随着MoB_(2)含量的增加从0.978降低至0.252。

Firstly, MoB_(2)powder was added to pure Ti to form TiB intermetallic compound by in-situ reaction, and then TiB/Ti matrix composites were prepared by non consumable arc melting furnace. Effect of TiB intermetallic compound on phase, microstructure and mechanical properties of the TiB/Ti matrix composites was studied by means of X-ray diffraction(XRD), optical microscope(OM), scanning electron microscopy(SEM), micro-hardness tester and universal material testing machine. The results show that the TiB/Ti matrix composites are mainly composed of α phase, α′ phase, β phase and TiB intermetallic compound phase. With the increase of MoB_(2)content, the Ti+MoB_(2)→α/α′(Ti)+β(Ti)+TiB phase transition occurs in the composites. The relative content of the TiB reinforced phase produced by in-situ reaction increases with the increase of MoB_(2)addition. The morphology of the TiB reinforced phase is short rod-like and fiber. In addition, with the increase of MoB_(2)addition, the compressive yield strength and microhardness of the TiB/Ti matrix composites increase significantly, while the compressive strain decreases gradually. When the addition amount of MoB_(2)is 7.5 mass%, the compressive yield strength and microhardness of the TiB/Ti matrix composites are 1095 MPa and 397 HV0.2, respectively, while the maximum compressive strength and compressive strain are 1337 MPa and 13.0% respectively. The work hardening index of the TiB/Ti matrix composites decreases from 0.978 to 0.252 with the increase of MoB_(2)content.