Oxide dispersion strengthened and oxidation resistant vanadium alloys

钒基合金具有很高的机械强度，是开发新型高温材料的有希望的候选者。这可以通过与引起沉淀硬化的元素（如Si和B）或氧化物颗粒，即所谓的ODS颗粒（氧化物分散体）合金化来实现。然而，最佳力学性能要求材料微观结构中有一个V型固溶体矩阵。而这种基质在氧化环境中又极其脆弱。原因是V2O5的形成——与纯金属（Ts（钒）= 1919°C）相反——在大约690°C以上的温度下是液态的。这种氧化行为是钒基合金直到现在还没有考虑高温应用的原因。更糟糕的是，钒酸盐在不同的氧化态之间很容易发生变化，这极大地加速了镍、钴或铁基材料的高温腐蚀，尤其是当它以熔融形式存在时。这也不包括目前可用的钒合金与这些材料结合的应用。为了使钒合金适用于高温环境，提出了一种全新的氧化颗粒同时强化氧化保护的方法：利用含镁和含钙的氧化颗粒制备抗氧化ODS-V-Si合金。引入足够量的ODS颗粒有望在高温下防止液相的形成。同时，我们预计颗粒的强化效应，这是量化的潜在应用范围从室温到1100℃的合金。这个项目的目的是澄清(1)采用的体积分数,曹或正硅酸镁颗粒均匀的微观结构可以形成钒材料,(2)分别以浓度,曹或硅酸镁需要防止液相形成或触发一个自我保护的机制,(3)多大的加强效应可以通过添加氧化物分散体和ODS粒子如何影响钒合金的蠕变行为。为了系统地描述粉末和合金系统的组成和微观结构，以及随后的氧化行为，计划进行相应的研究。研究的重点在于确定ODS颗粒与钒固溶体的最佳配比与抗氧化性能和力学性能的关系。因此，采用了一种全新的合金设计方法，同时提高了合金的抗氧化性和力学性能。

Vanadium-base alloys are promising candidates for the development of novel high temperature materials due to, among others, their highly specific mechanical strength. This can be achieved by alloying with elements that cause precipitation hardening (such as Si and B) or with oxide particles, so-called ODS particles (oxide dispersoids). However, optimal mechanical properties require a V solid solution matrix in the materials microstructure. This matrix in turn is extremely vulnerable in oxidising environments. The reason is that the formation of V2O5, which – in contrast to the pure metal (Ts (Vanadium) = 1919 °C) – is liquid at temperatures above ca. 690°C. This oxidation behaviour is the reason why vanadium-base alloys have not been considered for high temperature application until now. To make matters worse, vanadate changes very easily between different oxidation states, which extremely accelerates the high temperature corrosion of Ni-, Co- or Fe-base materials, especially if it is present in a molten form. This also excludes an application of currently available vanadium alloys in combination with these materials.In order to make vanadium alloys applicable at high temperatures, a completely new approach of oxidation protection is proposed with simultaneous oxide particle strengthening: Using Mg- and Ca-containing oxide particles to produce oxidation-resistant ODS-V-Si alloys. Introduced in sufficient amounts, the ODS particles are expected to prevent the formation of liquid phase at high temperatures. At the same time we expect a strengthening effect of the particles, which is to be quantified in the potential application range of such alloys from ambient temperature to 1100°C.The purpose of the project is to clarify (1) up to which volume fraction of MgO, CaO or magnesium orthosilicate particles homogeneous microstructures can be formed in vanadium materials, (2) which concentration of MgO, CaO or magnesium orthosilicate is required to prevent liquid phase formation or to trigger a self-protecting mechanism, (3) how much of a strengthening effect can be achieved by adding oxide dispersoids and how the ODS particles affect the creep behaviour of vanadium alloys. Accompanying investigations are planned in order to systematically characterise the powder and alloy systems in terms of their composition and their microstructure and, subsequently, their oxidation behaviour. The main focus lies on determining the optimal ratio between ODS particles and vanadium solid solution in relation to oxidation resistance and mechanical properties. Thus, a completely new approach of alloy design is taken in order to improve oxidation resistance and mechanical properties at the same time.