Determination of Creep Mechanisms and Modeling Low Temperature(<0.25Tm) Creep of Two-Phase Titanium Alloys

技术概要：两相合金，特别是钛合金在技术上是重要的。钛合金具有高的强度比、优良的耐腐蚀性和生物相容性等优良性能。由于这些原因，它们被用于许多高技术领域。在许多这些应用中，组件在低温（0.25Tm）下长时间承受恒定载荷。最近，许多意想不到的结果已被报道，这是非常重要的设计和选择钛合金的各种应用。例如，已经表明，传统上被认为是非常快的变形机制的孪生可以非常缓慢地发生。此外，由于孪晶，单相#945;和#946;钛合金可在低温下蠕变（即塑性变形）。还发现，由于相之间的相互作用，两相#945;-#946;钛合金的变形机制可以与单相合金的变形机制完全不同。这种行为的确切原因尚不清楚。本研究的目的是系统地研究#945;-#946;钛合金的低温蠕变作为#945;和#946;相的体积分数和形态的函数;使用三种不同的Ti-V合金作为模型系统。晶体学建模以及三维各向异性有限元建模将用于确定相之间的相互作用。扫描电子显微镜和透射电子显微镜将用于确定变形机制。基于这些结果，将确定用于改进低温抗蠕变性的最佳微观结构。非技术概要：在许多应用中，载荷在低温（如室温）下施加在结构构件上。有时，在长时间段内将载荷施加在这些结构上，这可能导致与时间相关的变形，即蠕变。这项研究的重点是确定最佳的化学和微观结构的两相结构材料，如钛合金的低温蠕变阻力。将通过参加各种技术会议和在知名期刊上发表文章，广泛宣传研究结果。虽然低温蠕变变形的研究是基于两相钛合金，但其结果预计将有助于复合材料的广泛领域。在这次调查中，研究生将接受先进的建模和实验技术的培训。这些研究生将继续在工业，政府或教育领域担任技术职务。除了参加各种国家和国际会议外，该项目还通过“材料优势学生分会”等活动，促进与社区和多样性的联系。首席研究员是马里兰州大学，学院公园材料优势学生章的创始教师顾问。本章积极参与开放的房子在大学教育公众对材料科学。此外，本章鼓励本科生和研究生参加各种国家专业协会会议。

TECHNICAL SUMMARY:Two-phase alloys in general and &amp;#945;-&amp;#946; titanium alloys in particular are technologically important. The attractive properties of titanium alloys include high strength to weight ratio, excellent corrosion resistance and biocompatibility. For these reasons, they are used in a number of high technology areas. In many of these applications, components are subjected to constant loads over extended periods of time at low temperatures (0.25Tm). Recently, many unexpected results have been reported which are of great importance in designing and in selecting titanium alloys for various applications. For example, it has been shown that twinning, which has traditionally been known to be a very fast deformation mechanism, can occur very slowly. Further, due to twinning, the single-phase &amp;#945; and &amp;#946; titanium alloys can creep (i.e. plastically deform) at low temperatures. It was also found that the deformation mechanisms of the two-phase &amp;#945;-&amp;#946; titanium alloys can be quite different than those of the single phase alloys due to interactions between phases. The exact reasons for this behavior are not known. The aim of this investigation is to systematically study the low temperature creep of &amp;#945;-&amp;#946; titanium alloys as a function of volume fraction and morphology of &amp;#945; and &amp;#946; phases; using three different Ti-V alloys as the model systems. Crystallographic modeling as well as three-dimensional anisotropic finite element modeling will be used to determine the interactions between phases. Scanning electron microscopy and transmission electron microscopy will be used to determine the deformation mechanisms. Based on these results, optimal microstructures for improved low temperature creep resistance will be identified.NON-TECHNICAL SUMMARY:In a number of applications, loads are applied on structural members at low temperatures such as room temperature. At times, loads are applied on these structures over extended periods of time, which can result in time-dependent deformation, i.e. creep. This investigation focuses on determining optimal chemistry and microstructures of two-phase structural materials such as titanium alloys for low temperature creep resistance. The results will be widely publicized through participation in various technical conferences and publication in reputed journals. While this study of low temperature creep deformation is based on two-phase titanium alloys, the results are expected to contribute to the wide field of composite materials in general. During this investigation, graduate students will be trained in advanced modeling and experimental techniques. These graduate students will then go on to take up technical positions in industry, government, or education. In addition to participation in various national and international conferences, this project also promotes outreach to the community and diversity through such activities as the Materials Advantage Student Chapter. The Principal Investigator is the founding faculty advisor for the University of Maryland, College Park Materials Advantage Student Chapter. This chapter actively participates in open-houses at the University to educate the public on materials science. Further, this chapter encourages both undergraduate and graduate students to participate in the various national professional society meetings.