钛合金轻质高强，在航空航天航海等领域具有广泛的应用前景。钛基复合材料是在钛合金中加入增强体以提高钛合金耐磨性、耐高温、比强度，在提高钛合金的综合力学性能、拓宽其应用前景方面具有很大的潜力。本文以增强体在基体中的空间分布对钛基复合材料的强韧化影响机制为基础，以热压烧结挤压和粉体预烧结-挤压两种工艺，在充分强化钛合金基体的同时，发挥增强体定向强化特性，制备出具有优异性能的增强体呈柱状网络分布的钛基复合材料，并对制备工艺进行了优化，同时研究了其强化机理和断裂失效机制。 首先选用热压烧结-挤压工艺制备出增强体呈柱状网络分布的钛基复合材料。以直径～110μm的TA15球形钛粉和平均粒径3μm的TiB₂为原材料采用低能球磨随后热压烧结的工艺，不同的原料配比，制备出不同TiB晶须含量的3D网状分布的TiBw／TA15复合材料，研究了TiB晶须含量对复合材料组织性能的影响。随后选择室温力学性能优异的2.5vol.％TiBw／TA15复合材料进行挤压制备出增强体呈柱状网络分布的钛基复合材料棒材。热挤压变形导致基体组织细化、TiBw沿挤压方向定向排布和基体连通性变好，从而进一步提高了复合材料的强韧性，在挤压方向上的拉伸强度和室温延伸率分别从1098MPa，6.2％增加到了1227MPa，10.2％。 为了缩短制备流程、降低成本以满足现代工业对产品高性价比的要求，采用粉体预烧结-包套挤压的工艺制备出增强体也呈柱状网络分布的钛基复合材料，并研究了挤压工艺参数(挤压温度和挤压比)对复合材料组织性能的影响，优化了工艺参数。通过对不同温度(α+β相区--950℃，接近β相变点--1050℃， β相区-1150℃)制备的钛基复合材料的室温力学性能及组织分析表明，挤压温度对晶须分布没有明显影响，但是使基体组织差异明显进而影响复合材料力学性能。当挤压温度在相变点附近时(1050℃)制备的复合材料出现了明显的晶界脆化现象，因此应避免在相变点附近进行挤压；当挤压温度为1150℃，复合材料呈现出优异的综合性能，室温强度和塑性分别达到1140MPa、7.8％。通过对不同挤压比(6:1、11:1、17:1)制备的钛基复合材料室温拉伸性能及组织分析表明，挤压比对晶须分布有明显的影响，基体组织都呈典型的动态再结晶组织。随着挤压比增大，复合材料中沿着挤压方向的织构明显增强，材料的强度逐渐提高，塑性逐渐降低。当挤压比为17:1时，基体和晶须出现了变形不协调的现象，因此对于TiBw增强钛基复合材料进行挤压变形时，挤压比不宜过大。 室温断裂机制研究表明，拉伸过程中，晶须先于基体发生断裂并产生微裂纹，但是裂纹会被基体钝化不会迅速扩展，从而使增强体呈柱状网络分布的钛基复合材料的强韧性得以充分发挥。高温断裂机制研究表明，分布在基体高温β相晶界的TiBw可以有效地强化晶界，形成高温‘晶界强化’效应，使柱状网络结构TiBw／TA15复合材料具有优异的高温性能，使用温度比基体TA15合金提高约100～150℃。但是当拉伸温度超过700℃时，基体发生软化，晶须与基体发生脱粘，TiB晶须已经不能强化基体。观察断口不同位置的组织可以定性分析复合材料室温和高温断裂过程及其断裂失效机制。 关键词：钛基复合材料；TiB晶须；热挤压；微观组织；力学性能

 Titanium alloys are light, high-strength and have a wide range of applications in many fields, such as aerospace and navigation. Titanium matrix composites (TMCs) have the potential to increase the wear resistance, high temperature resistance, and specific strength of titanium alloys by adding reinforcements into titanium alloys. It has great potential in improving the comprehensive mechanical properties of titanium alloys and broadening their application prospects. In this paper, based on the effect of the space distribution of the reinforcement in the matrix on the strengthening and toughening mechanism of TMCs, the two processes (reaction hot pressing-extrusion and powder extrusion) were used to prepare columnar structure TMCs bar with excellent properties, and the preparation process was optimized, and the strengthening mechanism and fracture mechanism were studied. Firstly, the columnar structure reinforced TMCs was prepared by reaction hot pressing-extrusion process. Using TA15 spherical titanium powder with a diameter of ～110μm and TiB₂ with an average particle size of 3μm as raw materials. Low-energy ball milling followed by hot-pressing sintering process and different raw material ratios were used to prepare TiBw/TA15 with 3D mesh distribution with different TiB whisker content to study the effect of TiB whisker content on the microstructure and properties of TMCs. Then, the 2.5vol.% TiBw/TA15 composites with excellent room-temperature properties were selected and extruded to prepare TMCs bars with reinforcements in columnar distribution. The hot extrusion deformation resulted in the refinement of the matrix, the distribution of TiBw along the extrusion direction and the better connectivity of the matrix, which further improved the strength and toughness of the composites. The tensile strength and elongation at room temperature in the extrusion direction were increased from 1098MPa, 6.2% to 1227MPa, 10.2%. In order to shorten the preparation process and reduce the cost to meet the high cost effectiveness requirements of modern industry, the columnar structure reinforced TMCs bars were prepared using powder extrusion process, and extrusion process parameters (extrusion temperature and extrusion ratio) were studied and the process parameters were optimized. The room-temperature mechanical properties and microstructure analysis of TMCs prepared at different temperatures (α+β phase zone--950℃, close to β phase transition point -- 1050℃, β phase zone--1150℃) indicated that the extrusion temperature had no obvious effect on the whisker distribution, but it made the matrix structure significantly different and then affected the mechanical properties of TMCs bar. When the extrusion temperature was near the phase transition point (1050℃), there was obvious grain boundary embrittlement in TMCs bar, so extrusion temperature should be avoided near the phase transition point; when the extrusion temperature was 1150℃, the composites appeared excellent overall performance, room temperature strength and plasticity could reach 1140MPa, 7.8%, respectively. The room temperature tensile properties and microstructure analysis of TMCs prepared with different extrusion ratios (6:1, 11:1, 17:1) showed that the extrusion ratio had a significant effect on the whisker distribution and the matrix structure was typical dynamic recrystallization structure. With the increase of the extrusion ratio, the texture along the extrusion direction in the composites was significantly enhanced, the strength was gradually increased, and the plasticity was gradually reduced. When the extrusion ratio reached 17:1, the deformation of the matrix and the whisker was inconsistent. Therefore, for TiBw reinforced TMCs, the extrusion ratio should not be too large. The room-temperature fracture mechanism results showed that during the stretching process, the whiskers broke before the matrix and then produced micro-cracks, but the cracks would not be propagated rapidly because they were blunted by the matrix, so that the columnar distribution of reinforcement brought the toughness of TMCs into full play. The high-temperature fracture mechanism results showed that TiBw distributed on the boundary of primary β grain could effectively strengthen the grain boundary forming high-temperature ‘grain boundary strengthening' effect, and then increased the high-temperature strength of the composite. The use temperature could be increased by about 100～150℃ compared to the matrix TA15 alloy. However, when the stretching temperature exceeded 700℃, due to softening of the matrix the whiskers were pulled out from the matrix, and the TiBw could no longer strengthen the matrix. Observing the different positions of tensile specimen could qualitatively analyze the room temperature and high temperature fracture process and fracture mechanism of TMCs. Keywords: titanium matrix composites (TMCs), TiBw, hot extrusion, microstructure, mechanical properties