(TiB2-SiC)复合陶瓷基团增韧B4C陶瓷的显微结构控制及增韧机理研究

B4C ceramics possess both ultra-high hardness and lightweight, which are unrivaled as typical structure ceramics. However, ultrahigh sintering temperature and low fracture toughness severely hinder its preparation and application. In this project, (TiB2-SiC) composite units are designed as composite toughening phases to toughen B4C ceramics, which breaks the toughening bottleneck of the independent phases as the toughening phases, thus greatly improving the fracture toughness of the B4C-(TiB2-SiC) composite ceramics. In addition, the high pressure hot pressing (80-120MPa) combining with two-step milling process, mechanochemistry- remixing, is developed to achieve controllable preparation of B4C-(TiB2-SiC) composite ceramics at relatively low temperature. The microstructure evolvement and synthesis mechanism of the composite powders during the mechanochemical process are explored. The formation, growth mechanism and distribution law of the (TiB2-SiC) composite units during the sintering are researched deeply. The densification and grain growth mechanism of the composite ceramics fabricated at high pressure are clarified. The new toughening mechanism of the B4C ceramics toughened by (TiB2-SiC) composite units is established. The research findings of this project are expected to provide the novel microstructure design idea and theoretical foundation for toughening the B4C and other structure ceramics.

碳化硼（B4C）陶瓷集超高硬度和轻质性于一身，这是其他结构陶瓷无法比拟的，然而，B4C陶瓷低的断裂韧性和极高的烧结温度阻碍了其广泛应用。本项目突破目前B4C复合陶瓷均以分散的独立物相作为增韧相的增韧瓶颈，设计一种以（TiB2-SiC）复合陶瓷基团作为复合增韧相的B4C-(TiB2-SiC)复合陶瓷以大幅度提高B4C材料的断裂韧性，并发展一种机械化学法--再混合两步制粉工艺结合高压热压（80-120MPa）烧结技术来实现这种特殊结构复合陶瓷的低温、可控制备。同时，探索机械化学过程中复合粉体结构演化规律和合成机理；重点研究烧结过程中（TiB2-SiC）复合增韧基团的形成、生长机制和分布规律；阐明高压热压条件下复合陶瓷的致密化机理和晶粒生长机制；构建（TiB2-SiC）复合陶瓷基团增韧的B4C复合陶瓷的新型增韧机理。本项目研究成果预期为B4C及其他结构陶瓷的增韧研究提供新的设计思路和理论依据。

碳化硼（B4C）作为一种重要的结构工程材料，除了具有结构陶瓷共有的高硬度、耐磨损、抗腐蚀、耐高温等优点外，其最为独特的优点是集超高硬度与轻质性于一身，这是其他结构陶瓷无法比拟的。然而，B4C陶瓷低的断裂韧性和极高的烧结温度阻碍了其广泛应用。目前，国内外对于B4C复合陶瓷增韧研究的思路一直禁锢在以的独立物相弥散增韧结构为模板，通过简单的替换增韧相种类，然后验证这种增韧相对B4C陶瓷增韧效果。虽然不同独立增韧相对B4C增韧效果有所差异，但是由于增韧结构基本相同，导致它们增韧效果差异并不大，备出的各种B4C复合陶瓷的断裂韧性徘徊在3-6MPa•m1/2之间，无法获得进一步突破，B4C复合陶瓷的增韧研究遇到瓶颈。. 针对上述问题，本项目设计一种以（TiB2-SiC）复合陶瓷基团作为复合增韧相的B4C-(TiB2-SiC)复合陶瓷，从而突破目前独立物相增韧效果的局限性，打破B4C复合陶瓷增韧瓶颈，实现B4C复合陶瓷韧性的进一步提升（>7MPa•m1/2）；同时发展一种机械化学法-再混合两步制粉工艺，即首先通过机械化学法制备出具有高活性的超细非晶TiB2-SiC复合粉体，然后以此TiB2-SiC复合粉体和B4C粉体为原料通过二次混合制备出具有特殊结构的B4C，TiB2-SiC混合粉体，以保证烧结过程中B4C基体内(TiB2-SiC)复合增韧基团的可控形成；并采用高压热压（80-120MPa）工艺以降低该复合陶瓷的烧结温度。与此同时，探索机械化学过程中TiB2-SiC复合粉体的结构演化规律和合成机理；重点研究烧结过程中复合增韧基团（TiB2-SiC）的形成、生长机制；阐明高压热压条件下复合陶瓷的致密化机理；构建以（TiB2-SiC）复合基团作为增韧相的B4C复合陶瓷的新型增韧机理。研究成果在耐磨陶瓷部件、航空航天和国防建设领域具有重要的应用价值。这种以复合陶瓷基团作为增韧相去增韧基体的设计理念、增韧机理及关键制备技术也为其他结构陶瓷的增韧研究提供新的研究思路和理论支持。