原位合成不同基体组织7715D钛基复合材料的高温力学性能

High-Temperature Mechanical Properties of In-Situ Synthesized 7715D Titanium Matrix Composites with Different Matrix Microstructures

利用真空电弧熔炼技术,通过热加工原位合成了以TiB纤维和La_2O_3颗粒为增强体的7715D钛基复合材料,然后分别在β相区与(α+β)相区退火,获得层片和等轴两种基体组织;并对不同组织复合材料进行了高温拉伸试验、蠕变试验和不同温度下的热暴露试验。结果表明:与等轴组织相比,层片组织显著提高了复合材料的高温抗拉强度及蠕变性能,能有效阻止增强体断裂后微裂纹的扩展;在600℃下热暴露时,复合材料的热稳定性最差,主要由在等轴组织初生α相中和层片组织的α片边界处析出颗粒状脆性相所致,其对复合材料室温塑性均有不利影响。

7715D titanium matrix composites （TMC） reinforced with TiB fibres and La20a particles were insitu synthesized through heat treatment by vacuum arc melting process. Lamellar and equiaxed microstructure could be obtained after annealed in β phase and （α＋β） phase, respectively. High-temperature tensile test, creep test and heat exposure test at different temperatures were carried out for the composites with different microstructures. The results show that comparing with equiaxed microstructure, the lamellar microstructure obviously improved the high- temperature tensile strength and creep property of the composites, it could retard the micro-crack propagation after the reinforcement fracture effectively. After heat exposure at 600 ℃, the composites had the worst thermal stability, which due to the precipitation of granular brittle phases in the primary a phase of equiaxed microstructure and at the grain boundaries of lamellar microstructure. It was harmful to room temperature plasticity of the composites.