MAX相结合剂金刚石复合材料微波强化自蔓延烧结机理研究

MAX phase is considered as a novel binder for the fabrication of diamond grinding tools. Self-propagation high temperature sintering (SHS) is an efficient strategy to fabricate the MAX phase/diamond composite. However, it is an crucial dilemma that the precise control for the microstructure and interfacial situation, which results from the heterogeneous reaction in the interior space. In this proposal, the single powders for the compose of typical MAX phase, will be adopted as a raw. And the microwave field with the characteristic of selective heating and internal heating will be introduced in SHS method. The proposal mainly attempts to obtain the dynamic variation of material electromagnetic properties in the SHS reaction process, and to confirm the indispensable critical micro-architectural information, including the existing state of elements in the sintered compact, the constitute and structure of interfacial transition layer, the distribution feature of pores structure and the binding situation of diamond abrasives. Through aforementioned investigation, we aim to obtain the correlative law between parameters of microwave strengthening self-propagation high temperature sintering, to explore the microstructure evolution behavior under different process conditions, to clarify the strengthening mechanism of multicomponent transfer and interfacial reaction in the microwave field, to establish a novel theory of strengthening migration and interfacial reaction, and finally to propose a neoteric prototype and process. The implementation of this project will provide a fancy idea for the preparation of MAX phase ceramic matrix diamond composite, and the formed generic technology and sintering mechanism can provide theoretical reference to the scale production of similar diamond grinding tools.

MAX相是陶瓷基金刚石磨具的新型结合剂，自蔓延烧结是高效低耗制备MAX相/金刚石复合材料的有效方法，然而样品内部空间反应不均匀导致微结构和界面状态难以精确调控是传统自蔓延烧结面临的关键问题。本项目拟以典型的MAX相组元单质粉体为原料，将微波场引入自蔓延烧结反应，利用微波选择性加热和内部整体加热特性，重点研究物料在自蔓延烧结过程中的微波电磁特性变化规律，分析烧结组织元素赋存分布状态、界面过渡层物相组构、孔结构分布特性、金刚石结合状态等微结构信息，进而获得微波强化自蔓延烧结工艺参数的关联规律，探索微结构演变行为，揭示组元迁移与界面反应过程的强化机制，构建自蔓延烧结过程元素强化迁移规律及界面反应理论，形成微波强化自蔓延烧结制备MAX相/金刚石复合材料的技术原型和新方法。项目的实施为MAX相陶瓷金刚石磨具的制备提供了一种新的技术思路，形成的共性技术和烧结机理可为该类工具的规模化生产提供理论借鉴。

利用微波加热速度快和内部整体受热等优点，通过研究MAX相陶瓷结合剂配方在微波场中电磁特性，获得了不同诱发条件下的微波热爆法自蔓延烧结工艺，阐明工艺参数对样品微观结构和力学性能的影响，获得基于热爆法机制的自蔓延微波烧结制备MAX相金刚石复合材料的高效低耗烧结新工艺和理论。研究结果如下：(1) 测定了以典型MAX相原料配方的高温动态电磁特性，获得样品在微波场中的温度分布特征，原料表现出良好吸波特性，从理论层面验证新方法的可行性。（2）针对Ti-Al-C/金刚石微波自蔓延烧结开展了系统研究，获得了基于“微波”、“等离子体”、“热辐射”三类自蔓延诱导方式下的烧结工艺和微结构演变之间的关系，基体中形成板条状Ti3AlC2相和过渡层与金刚石结合紧密并形成良好把持；（3）Ti-Al-C/金刚石体系微波诱导SHS烧结基体优选配方为Ti28Al50C7-15%金刚石，Al含量30%和50%烧结产物分别为TiC和Al3Ti；等离子体诱导微波SHS配方为3Ti/Al/2C-20%金刚石，生成Ti3AlC2、Ti2AlC、Al3Ti和TiC相；热辐射诱导微波SHS配方为3Ti/1.2Al/2C, 在1300℃诱发自蔓延生成的Ti3AlC2晶粒均匀。（4）获得Ti-Si-C、Cu-Ti-C、Al-TiO2-C三种陶瓷基体的配方，通过XRD、SEM、EDS等研究微波SHS工艺（烧结温度、烧结助剂）、微结构（断口形貌、孔结构）以及服役性能之间的关系。结果表明，高热值Ni-Al合金600℃下可诱发Ti-Si-C自蔓延反应；Cu含量80%的Cu-Ti-C体系烧结样品组织致密，形成的CuTix、TiC、CuTix等物相增强基体硬度；3TiO2/4Al/3C-10%金刚石中添加铝可显著降低烧结温度，有效避免金刚石磨料的热损伤。（5）MAX陶瓷粉体在微波场中通过自身介电损耗效应实现原子层面的能量原位转换，微波通过增加原子的活性加快自蔓延元素迁移，内部加热使样品产生由内到外温度梯度，在快速自蔓延烧结后可维持烧结组织的快速致密化。通过项目实施，共发表论文21篇，其中SCI/EI检索16篇；申请专利12件，其中授权发明专利6件，授权实用新型3件；参加国内外学术会议6次；开展国际合作人员交流互访3人，联合举办学术讲座17场，项目负责人赴加拿大阿尔伯塔大学访学；培养硕士研究生5名。