Non-Isothermal Viscoplasticity in Metals

金属的非等温粘塑性

• 批准号: 1950027
• 负责人: Jean-Briac le Graverend
• 金额: $ 48.8万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1950027&HistoricalAwards=false
• 关键词: Non; Isothermal; Viscoplasticity; Metals

Metals tend to creep or deform permanently under constant mechanical stress at elevated temperatures leading to failure. Based on data obtained from material testing at elevated but constant temperatures, it has been generally assumed that the higher the operating temperatures the shorter the lifetime of metallic applications. This award supports fundamental research to understand how varying temperature with time towards higher values could enhance creep performance of metals. This new knowledge will address the need to increase operating temperatures in key industrial sectors, such as aerospace and electricity generation, to improve efficiency and reduce environmental impact, without compromising safety. Insights from this project will ultimately be used by metallurgists to design materials that are better suited for higher thermo-mechanical loading. This award also supports an attractive educational platform for a diverse group of high school, undergraduate and graduate students, including female and minority students, through exposure to STEM topics and participation in laboratory research.The underlying hypothesis of this project is that the lattice misfit between phases in Nickel-based superalloys under certain non-isothermal loadings plays an essential role in enhancing creep performance at elevated temperatures. The project, therefore, rests on the transformative paradigm that “hotter can be longer” depending on how the coherency stresses evolve. To test this hypothesis, the lattice misfit evolution will be tracked in new temperature/stress regimes by in situ X-ray diffraction under synchrotron radiation. In situ results will be used to correlate, at the macroscale, the non-isothermal mechanical responses. Furthermore, discrete dislocation dynamics simulations will be carried out to gain further insight into dislocation/precipitate interactions depending on the microstructural state and lattice misfit. These simulations will help identify and quantify competing mechanisms, e.g., climb/glide and self-interaction/precipitate hardening effects, which will qualitatively help explain experimental results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

金属倾向于在升高的温度下恒定的机械应力下永久蠕变或变形，导致衰竭。基于从升高但恒定温度下的材料测试获得的数据，通常认为工作温度越高，金属应用的寿命越短。该奖项支持基本研究，以了解如何随着时间的流逝而朝着更高的价值朝着更高的价值迈进的变化可以增强金属的蠕变性能。这一新知识将满足提高关键工业部门（例如航空航天和发电）的运营温度的需求，以提高效率并降低环境影响，而不会损害安全性。冶金学家最终将使用该项目的见解来设计更适合更高机械加载的材料。该奖项还为一个高中，本科和毕业生的潜水员小组提供了一个有吸引力的教育平台。包括女性和少数族裔学生在内的学生通过暴露于STEM主题并参与实验室研究。该项目的基本假设是，在某些非等温载荷下，基于镍的超合金中的阶段之间的晶格级别在提高升高温度下的蠕变性能方面起着至关重要的作用。因此，该项目取决于变革性范式，即“较热可能更长”，具体取决于相干性压力的发展方式。为了检验这一假设，将在同步加速器辐射下通过原位X射线衍射在新的温度/应力状态下跟踪晶格级传播的演化。原位结果将用于在宏观上与非等热机械响应相关联。此外，将进行离散的脱位动力学模拟，以进一步了解脱位/沉淀相互作用，具体取决于微观结构状态和晶格失误。这些模拟将有助于识别和量化竞争机制，例如攀爬/滑行和自我交互/沉淀效应，这将在定性上有助于解释实验结果。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的审查标准来通过评估而被认为是珍贵的支持。