新型锆合金强韧化途径与机制

Today’s industry has been largely relied on the development of steel, aluminum alloys, titanium alloys and magnesium alloys. But as the working condition of the machine parts is going to reach the critical point for the materials to bear, new materials are urgently needed to satisfy the worse and worse condition. Zirconium based alloy is one of them. Zirconium and its alloys are of great practical value in nuclear industry and chemical industry due to their excellent physical and chemical properties, such as good anti-irradiation, corrosion resistance, oxidation resistance and small neutron absorption area. But there are few other applications reported for Zr-based alloys as other structural materials, which is not restricted by the costs but the lack of effective strengthening and toughening methods. The key issue to be studied to make Zr-alloys suitable for other structural materials is to find the best approach to strengthen and toughen them and to reveal the physical mechanisms underlying the preparation of highly strengthened Zr-alloys. In this project, the Zr-based alloys systems are going to be designed from electronic structure, phase and microstructure control. The phase and microstructure evolution of the Zr-based alloys during solidification, heat treatment and deformation processes will be investigated to unveil the effect of composition, heat treatment and deformation parameters on the phase evolution and the final microstructures. In this project, it will also be an important issue to solve the problem that the mechanical properties are largely affected by the coarse microstructure often appeared in the traditional Zr-based alloys, and to improve the mechanical properties of the newly developed Zr-based alloys. The application potential of the newly-developed Zr-based alloys as the moving parts in some mechanisms in space, and as parts in corrosion resistant areas as well as in polluted water treatment area, will be investigated.

钢铁、铝合金、钛合金、镁合金等金属结构材料为现代工业发展做出了重要贡献。随着技术进步，材料的服役环境越来越苛刻，迫切需要开发具有特殊使用性能的新金属结构材料，锆合金就是其中之一。锆及其合金具有中子吸收截面小、抗辐照、抗腐蚀等特点，在核工业和醋酸工业中具有非常重要的应用价值。除此之外，锆合金作为结构材料在其它领域的应用却非常少见，究其原因，并非成本问题（成本与钛合金相当）而是缺少有效的强韧化手段。本课题从电子结构和相与组织调控角度设计新型高强韧锆合金。研究在凝固、热处理、变形等过程中的相组成和组织演化规律，查明合金成分、热处理工艺、变形条件对合金相组成的影响机制。探索获得细化组织的新途径，解决锆合金组织粗大影响力学性能的突出问题，提升新开发锆合金的综合力学性能。为实现新开发锆合金在空间机构关键构件以及在耐酸、碱、盐和污水处理等领域的应用奠定基础。挖掘锆合金的应用潜能，突破锆合金的应用局限性。

本项目通过研究锆及锆合金的相变规律并结合成分设计理论开发了一系列新型高强韧二元、三元及多元锆合金体系，将多种工业化加工及热处理手段应用于实验室的合金制备上，通过调节工艺参数和开展广泛大量的试验，探明了各合金元素、变形工艺、热处理工艺对合金相成分、显微组织结构和力学性能的影响，实现了对各系列新型高强韧锆合金组织性能的精准调控。一方面，针对锆合金的强韧化机制，我们优先利用理论计算为随后的试验做指导，分析了基体元素与溶质合金元素的平均共价键强度和各元素的平均d轨道能级之间的关联，再用第一性原理计算得到不同体系锆合金的结合能来表征合金元素对其形成β相的稳定性能力，研究了锆合金中的相的稳定性及弹性特性，从而开发出含钛、铝、硼、铍、钒等元素的新型锆合金体系。另一方面，在前期理论研究的基础上利用轧制、锻造或其他变形加工方式，同时结合不同的热处理工艺对合金样品进行处理，研究了加工工艺对合金相组成和显微组织的影响，通过L12型化合物的析出强化实现了锆合金的强度和塑性协同增长，发现了锆合金中的新型强化机制，如应力诱发α'相，能够依靠高的加工硬化率获得高的抗拉强度，实现了一系列新型锆合金的强韧化。本项目中的研究方法和制备技术可为实际工业化生产提供有力的科学保障。