【作者】 王磊；

【导师】 黄振莺；

【作者基本信息】 北京交通大学 ， 机械（专业学位）， 2022， 硕士

【摘要】 金属-陶瓷双连续相复合材料是一种金属相和陶瓷相成连续三维网络结构的新型多功能材料,其中陶瓷相可以降低密度,并且可以提高材料强度,减少热膨胀。而金属相可以改进材料的韧性,在高温下的发汗冷却作用还能对陶瓷基体起到一定的保护作用。因此,它可以作为一种轻量化的耐烧蚀材料应用于加工固体火箭发动机燃气舵、喉衬等耐热抗烧蚀部件。本论文以纳米乙炔炭黑和Ti粉为初始原料,通过原位反应烧结法制备了不同气孔率的非化学计量比的多孔TiC_x（x=0.7）预制体,然后在无压条件下将熔融金属Cu浸渗入预制体,制备了双连续相TiC_x/Cu复合材料,系统分析了TiC_x的气孔率、陶瓷晶粒尺寸与形貌对TiC_x/Cu双连续相复合材料的微观结构和物相形态的影响。测试分析了TiC_x/Cu双连续相复合材料的常温、高温力学性能以及耐烧蚀性能,研究结果如下:（1）将摩尔比为1:0.7的Ti粉和纳米乙炔炭黑进行混料,通过热压烧结技术制备出TiC_x预制体,分别控制烧结压力以及烧结温度调控气孔率和晶粒尺寸。预制体具有足够的骨架强度,孔隙连通,满足无压浸渗对预制体的要求。采取无压浸渗工艺,将熔融状态的金属Cu浸入TiC_x预制体,获得金属相和陶瓷相成连续三维网络结构的TiC_x/Cu双连续复合材料。（2）TiC_x/Cu双连续相复合材料的弯曲强度和断裂韧性随预制体气孔率增加而提高,1600℃-3 MPa制备的预制体对应的复合材料,弯曲强度可达到1052±59MPa,断裂韧性为11.9±2.7 MPa·m^1/2。压缩强度主要与陶瓷骨架强度有关,其中1700℃-3 MPa制备的预制体对应的复合材料压缩强度可达1436±111 MPa。（3）TiC_x/Cu双连续相复合材料具有优良的高温力学性能。在400℃和600℃下,1700℃-3 MPa制备的预制体对应的复合材料压缩强度为1340±64 MPa和733±77 MPa。1600℃-7 MPa制备的预制体对应的复合材料的弯曲强度在400℃达到了925±40 MPa;1600℃-3 MPa制备的预制体对应的复合材料的弯曲强度在600℃达到387±11 MPa;900℃时,1700℃-3 MPa制备的预制体对应的复合材料的弯曲强度为109±12 MPa。高温力学性能受陶瓷骨架强度、金属相含量、金属热膨胀对两相机械结合的加强以及强化相的生成综合影响。（4）TiC_x/Cu双连续相复合材料具有优良的抗烧蚀性能。在30 mm-40 s条件的使用氧-乙炔火焰对1700℃-3 MPa制备的预制体对应的复合材料进行烧蚀,线烧蚀率为0.0485 mm/s,优异的抗烧蚀性能与较高的陶瓷骨架密度和连续程度以及铜的发汗冷却作用有关。烧蚀后TiC_x的x值以及晶粒尺寸增大,有利于增强骨架抗冲刷能力。烧蚀机理主要包括热物理烧蚀、热化学烧蚀以及机械剥蚀三种。更多还原

【Abstract】 As a novel kind of multifunctional materials,bicontinuous composites composed of metal and ceramic phases are characterized by a continuous three-dimensional network structure,in which the ceramic phase plays a significant role in reducing the density、thermal expansion and enhancing the material strength while the metal phase is subjected to the toughness improvement,sweating and cooling effect at high temperatures.Therefore,it tends to be a prospective candidate as lightweight and ablation-resistant material used for solid rocket engine gas rudders,throat liners and other heat and ablation-resistance parts.In this thesis,porous TiC_x（x=0.7）preforms with different porosity and substoichiometric ratios were firstly prepared by in situ reactive sintering using nanoacetylene carbon black and Ti powders as initial raw materials.Then the bicontinuous TiC_x/Cu composites were prepared by infiltrating molten metal Cu into the preforms under pressureless conditions.The effects of the porosity of TiC_x,ceramic grain size and morphology on the microstructure and phase morphology of TiC_x/Cu bicontinuous composites were systematically analyzed.The mechanical properties of resulted composites at room and high temperature as well as the ablation resistance of TiC_x/Cu bicontinuous composites were tested and analyzed.The main results in this thesis were as follows.（1）TiC_x preforms were fabricated by hot-pressure sintering Ti powder and nanoacetylene carbon black mixtures with a molar ratio of 1:0.7,and the porosity and grain size were regulated by controlling the sintering pressure as well as the sintering temperature,respectively.The preform was endowed sufficient skeletal strength and pore connectivity which met the requirements of the preform for pressureless infiltration.The TiC_x/Cu bicontinuous composite material with continuous three-dimensional network structure composed of metal and ceramic phases was obtained by infiltrating molten metal Cu into the TiC_x preform under the pressureless process.（2）The bending strength and fracture toughness of TiC_x/Cu bicontinuous phase composites increased with increament of the porosity of preform.The composite corresponding to the preform prepared at 1600℃-3 MPa could reach 1052±59 MPa in bending strength and 11.9±2.7 MPa·m^1/2 in fracture toughness.The compressive strength was mainly related to the strength of ceramic skeleton.The compressive strength of the composite corresponding to the preform prepared at 1700℃-3 MPa can reach 1436±111 MPa.（3）The TiC_x/Cu bicontinuous phase composites exhibited excellent high temperature mechanical properties.At 400℃ and 600℃,the compressive strengths of the composite corresponding to the preform prepared at 1700℃-3 MPa were determined to be 1340±64 MPa and 733±77 MPa,respectively.The bending strength of the composite corresponding to the preform prepared at 1600℃-7 MPa reached 925±40 MPa at 400℃;the bending strength of the composites corresponding to the preform prepared at 1600℃-3 MPa reached 387±11 MPa at 600℃;the residual bending strength of the composites corresponding to the preform prepared at 1700℃-3MPa could also reach 109±12 MPa at 900℃.The high-temperature mechanical properties are affected by the combination of the ceramic skeleton strength,the metal phase content,the strengthening of the mechanical bonding of the two phases by the thermal expansion of the metal,and the generation of the reinforcing phases.（4）The TiC_x/Cu bicontinuous phase composites preform superior ablation resistance.The composites corresponding to the preform prepared at 1700℃-3 MPa were ablated using an oxygen-acetylene flame at the condation of 30 mm-40 s.The line ablation rate was determined to be 0.0485 mm/s.The excellent ablation resistance wa s related to the higher density and continuity of the ceramic skeleton and the sweat-cooling effect of copper.The increment of x value in TiC_x as well as the grain size after ablation is beneficial to enhance the resistance to scouring.The ablation mechanisms are mainly consisted of thermophysical ablation,thermochemical ablation,and mechanical exfoliation.更多还原