微量元素（Ti、Zr、C）对核聚变堆钨基材料的强韧化及机理研究

The development of fusion requires that tungsten-based plasma facing materials (PFM) have high performance, such as high room temperature toughness, high temperature strength, high recrystallization temperature and good irradiation resistance. However, pure tungsten exhibits severe embrittlement in several aspects, including room temperature brittleness, recrystallization brittleness and irradiation-induced brittleness. The low temperature brittleness of tungsten is strongly related to the segregation of trace interstitial impurity elements (O, C, N) on grain boundaries, which forms brittle membrane layer and decreases the bonding strength of grains, and thus results in brittle fracture. Therefore, controlling the distribution and forms of interstitial impurity elements (C, N, O), and strengthening grain boundaries become key points of improving mechanical properties of tungsten.?Therefore, in this project, the W-Zr-Ti-C alloys will be synthesized by spark plasma syntering method and/or microwave sintering method, the interaction between micro-alloying elements (Ti, Zr) and interstitial impurity elements (O, C, N), and the effect of micro-alloying on mechanical properties of tungsten and its mechanism would be studied. More specially, the influence of impurities in the grain boundaries on the mechanical properties and the effects of trace Ti, Zr and C on the cleaning and strengthening of grain boundaries will be concerned. The results of this project will provide theoretical and experimental foundation for the development of high-performance tungsten-based materials.

核聚变堆的开发要求面向等离子体钨基材料具有良好的室温韧性、高温强度、高的再结晶温度以及优越的抗辐照性能。然而，纯钨存在低温脆性、再结晶脆性、辐照脆化等缺点。其中，引起钨低温脆性的主要原因是O、C、N等杂质元素偏聚在晶界形成脆化层膜，造成晶界结合强度降低，从而导致晶间脆断。因此，如何调控钨晶界中杂质元素的分布、存在形态，净化与强化晶界，减少间隙杂质原子对晶界的脆化作用，是提高钨基材料力学性能的关键。对此，本项目将采用放电等离子烧结或微波烧结法制备W-Ti-Zr-C系块体合金，研究微量合金元素Zr、Ti等对钨中的O、N、C等间隙杂质原子的分布及存在形态的调控作用，以及对钨基材料力学性能的影响机制，特别关注晶界杂质含量对力学性能的影响规律以及Zr和Ti添加的晶界的净化和强化作用。项目研究成果将为高性能钨基材料的开发提供科学依据。

钨基材料由于具有高熔点、抗溅射、高热导率、低氚滞留等优点，是最有希望的聚变堆面向等离子体壁候选材料。然而，钨存在室温脆性、再结晶脆性、辐照脆化等不足，限制了其在聚变堆中的应用。钨中的微量杂质元素如O，C，N等在晶界处偏聚形成脆化膜层，是导致钨晶界结合力降低和低温韧性差的主要原因。因此，如何调控晶界中杂质元素的含量、分布和存在形态，减少杂质原子对晶界的脆化作用，是提高钨基材料力学性能的关键。本项目研究了微量Zr/Ti及其碳化物ZrC/TiC对钨基材料微结构和力学性能的影响机制，发现微量Zr/Ti能够与杂质O形成稳定的氧化物，从而净化钨晶界，提高低温韧性，但会降低钨的高温性能。通过在钨中添加高熔点的稀土氧化物颗粒，细化钨晶粒、提高钨合金的高温性能，同时添加微量Zr净化/强化晶界，提高韧性，制备了高强度、良好低温韧性的钨合金。在钨中添加少量ZrC纳米颗粒，不仅能够阻碍位错和晶界移动，细化晶粒，提高强度、在结晶温度，还能与杂质O生成Zr-C-O颗粒，从而降低O对晶界的脆化作用、提高韧性。在小样品优化的基础上，采用球磨+烧结+旋锻/热轧，制备了高性能钨合金棒材和板材。基于晶界净化/强化、弥散强化，成功研制出具有细晶粒（~1微米）、高强度/韧性、高再结晶温度的W-ZrC合金板材（10~15公斤/块），同时W-ZrC合金还具有优异的抗高热负荷冲击性能和抗等离子体辐照性能，成为最有希望的聚变堆面向等离子体壁材料之一。钨合金强韧化机理的相关为高性能钨基材料的研制打下了良好基础。