Development of novel Ti-based alloys with improved thermal-mechanical capability

开发具有改进的热机械性能的新型钛基合金

• 批准号: 524725651
• 负责人: Professorin Dr.-Ing. Bronislava Gorr
• 金额: --
• 依托单位: Institut für Angewandte Materialien - Werkstoffkunde (IAM-WK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/524725651?language=en
• 关键词: Development; novel; Ti; based; alloys

Commercially available high temperature Ti-based alloys possess a very attractive combination of low density, creep and fatigue resistance. These materials can, however, only be used up to a maximum temperature of approximately 550°C because of their limited intrinsic oxidation resistance. In this project, new oxidation-resistant Ti-based alloys with a thermal capability of up to 1000°C will be developed. These new materials should exhibit a favorable balance of (i) room temperature ductility/deformability, (ii) creep and oxidation resistance and (iii) low density. The oxidation resistance will rely on the formation of protective Cr-Ta-based oxide layers. In our previous studies, the minimal concentrations of Cr and Ta required for the formation of a continuous protective scale were determined. In the first step of project, ductile Ti-based alloys of different Mo/Ti ratios and a single-phase disordered bcc(A2) microstructure will be developed. The bcc(A2) crystal structure is stabilized by sufficient amounts of Ta, Mo, Cr and Ti. In the second step, the strength of these ductile alloys will be enhanced by (i) B2 precipitation strengthening of the A2 matrix (mimicking the  – ‘ microstructure of Ni-based alloys) or (ii) oxide dispersion strengthening by additions of Y2O3 dispersoids. Finally, in order to further improve the oxidation behavior and to reduce the alloy density, Ta will partially be substituted by Nb in the alloy exhibiting the best mechanical properties from previous steps. A density of below 7 g/cm3 is envisaged for the Ti-based alloys developed in this project. The alloy development concept is guided by thermodynamic modeling based on the CALPHAD (Calculation of Phase Diagram) approach. The feasibilty of the entire alloy concept will be validated by extensive experimental investigations of microstructure, mechanical properties and oxidation behavior.

商用高温钛基合金具有低密度、低蠕变和抗疲劳的极具吸引力的组合。然而，由于其有限的固有抗氧化性，这些材料只能在最高温度约550°C的情况下使用。在该项目中，将开发热性能高达1000°C的新型抗氧化钛基合金。这些新材料应该表现出(I)室温延展性/变形性、(Ii)蠕变和抗氧化性以及(Iii)低密度的良好平衡。抗氧化性将依赖于保护铬-钽基氧化层的形成。在我们以前的研究中，确定了形成连续保护层所需的最低铬和钽浓度。在项目的第一步，将开发出不同Mo/Ti比和单相无序体心立方(A2)组织的韧性钛基合金。足够数量的Ta、Mo、Cr和Ti稳定了bcc(A2)的晶体结构。在第二步中，通过(I)A2基体的B2析出强化(模仿镍基合金的-组织)或(Ii)添加Y_2O_3弥散强化氧化物来提高这些延性合金的强度。最后，为了进一步改善合金的氧化行为，降低合金密度，在前几步力学性能最好的合金中，用Nb部分取代Ta。该项目开发的钛基合金的密度预计在7g/cm3以下。合金开发理念以基于相图计算(CALPHAD)方法的热力学建模为指导。整个合金概念的可行性将通过对微观组织、力学性能和氧化行为的广泛实验研究来验证。