Thermal Stability and Mechanical Behavior of Ti-base Nanocrystalline Alloys

钛基纳米晶合金的热稳定性和力学行为

• 批准号: 1401725
• 负责人: Carl Koch
• 金额: $ 42万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1401725&HistoricalAwards=false
• 关键词: Thermal; Stability; Mechanical; Behavior; Ti

Non-technical Summary The thermal stability and mechanical behavior of selected titanium-base alloys with very small (nanocrystalline) grain sizes will be studied. The alloys will be prepared by the ball milling of powders that will then be consolidated by hot pressing. The structure and microstructures of the titanium alloys with appropriate additions of third elements that are predicted to stabilize the fine grain structure will be determined. Mechanical properties will be measured with techniques that evaluate the strength and ductility. Annealing studies will be carried out to quantitatively determine the thermal stability by measuring the growth of the fine grains. The results of these studies should have a substantial impact on both the processing and elevated temperature requirements of very fine grain size titanium alloys. Superior mechanical properties compared to conventional grain size titanium alloys can lead to breakthroughs in structural and bio-related (for example, implant materials) applications.Technical Summary Ti-base alloys processed to synthesize nanocrystalline microstructures with superior mechanical properties are of great interest for automotive and aerospace applications. These alloys are the focus of the proposed research. Powder compaction followed by elevated temperature consolidation is necessary to process the initial non-equilibrium alloys in most cases, and elevated temperatures are prerequisite for end-use. The research will investigate the kinetic and thermodynamic mechanisms that can provide high temperature thermal stability for nanocrystalline Ti-base alloys. Ti alloys with hcp alpha stabilizers and bcc beta stabilizers will be synthesized using mechanical alloying. A model will enable selection of optimum (oversize) solutes for thermodynamic stabilization. Kinetic stabilization by solute drag or Zener pinning will be achieved by in-situ (intermetallic precipitates) or ex-situ (oxide dopant) strategies. Thermal stabilization mechanism interactions and strengthening mechanism transitions (Hall Petch vs. Orowan strengthening) are highly relevant for achieving optimum microstructures. Microstructure characterization will be done using methods appropriate to the microstructural scale of interest. This will include structural and chemical investigation using state-of-the art instrumentation capable of atomic scale resolution. Mechanical properties will be measured with techniques that evaluate strength and ductility for the sample sizes produced by hot compaction of the processed powders. Isothermal annealing studies will be undertaken to establish grain-growth kinetics and activation energies. This will provide additional insight and modeling for stabilization mechanisms and interactions in selected temperature regimes.

非技术总结将研究具有很小（纳米晶）晶粒尺寸的选定钛基合金的热稳定性和机械行为。 合金将通过粉末铣削制成，然后通过热压加热。 将确定钛合金的结构和微观结构，并确定预测稳定细粒结构的第三个元素的适当添加。 机械性能将通过评估强度和延展性的技术来测量。 退火研究将通过测量细晶粒的生长来定量确定热稳定性。 这些研究的结果应该对非常细晶粒大小钛合金的加工和升高温度要求产生重大影响。 与传统的谷物尺寸钛合金相比，具有卓越的机械性能会导致结构和生物有关（例如，植入物材料）应用的突破。技术摘要Ti-base合金处理以合成具有卓越机械性能的纳米晶体微结构的纳米晶体微结构，对自动级和空间应用非常感兴趣。这些合金是拟议研究的重点。在大多数情况下，必须进行粉末压实，然后需要升高温度巩固，以处理初始的非平衡合金，并且温度升高是最终使用的先决条件。该研究将研究可以为纳米晶体Ti-碱合金提供高温热稳定性的动力学和热力学机制。具有HCPα稳定剂和BCCβ稳定剂的Ti合金将使用机械合金合成。模型将使最佳（超大）溶质选择热力学稳定。通过溶质阻力或齐纳固定的动力学稳定，将通过原位（金属间沉淀物）或前坐骨（氧化物掺杂剂）策略来实现。热稳定机制相互作用和加强机制过渡（Hall Petch vs. Orowan增强）与实现最佳微观结构高度相关。微观结构表征将使用适合微观结构量表的方法进行。这将包括使用能够原子量表分辨率的最先进的仪器进行结构和化学研究。机械性能将通过评估加工粉的热压实产生的样品量的强度和延展性的技术来测量。将进行等温退火研究，以建立晶粒生长的动力学和激活能。这将为所选温度制度中的稳定机制和相互作用提供其他见识和建模。