Effect of Alloying and Thermo-Mechanical-Treatment on Anisotropic Creep and Deformation of Ti-Alloys

该更新奖是DMR-0101309的更新奖，由数学和物理科学理事会材料研究部和工程理事会土木和机械系统部授予北卡罗莱纳州立大学，旨在研究热机械处理（TMT）和合金化对钛合金变形和蠕变各向异性的影响。获得该奖项后，Murty和Scattergood教授将利用封闭内压薄壁油管叠加轴向载荷来表征钛合金的各向异性双轴蠕变。该项目将研究Ti和Ti- 3al -2.5 v在去应力退火和完全再结晶后的这些行为。合金的添加，如Al到Ti，导致晶体织构和操作滑移系统的显著改变。冷加工导致Rx材料的等轴组织的晶粒形状各向异性。在不同的应力状态和应力水平下，研究这些变量对双轴加载后变形微观结构的影响以及变形各向异性。该奖项将研究蠕变机制的转变以及潜在变形机制对蠕变各向异性的影响。这样的研究将是重要的，因为“盲目”的短期数据外推到低应力可能导致“非保守”估计蠕变应变和这些结构材料的使用寿命。所提出的研究的更广泛的影响涉及到与技术相关的各种行业的结构材料，如航空航天、化工、运输等，在这些行业中，薄壁管在多轴载荷下的使用暴露非常关注可靠性。这些材料的力学各向异性，虽然使得预测结构寿命相对复杂，但为本科生和高中生提供了有趣的演示示例，从而使他们对现实生活中的问题有了很好的感觉。虽然拟议的研究结果与适当的技术直接相关，但这项研究涉及机械冶金和力学的基本方面。

This renewal award, a renewal of award DMR-0101309, by the Division of Materials Research in the Directorate for Mathematical and Physical Sciences and the Division of Civil and Mechanical Systems in the Directorate for Engineering to North Carolina State University is to study the influence of thermo-mechanical-treatment (TMT) and alloying on deformation and creep anisotropy of titanium alloys. With this award, Professors Murty and Scattergood will characterize the anisotropic biaxial creep of Ti alloys using closed-end internally pressurized thin-walled tubing superimposed with axial load. The project will investigate these behaviors in Ti and Ti-3Al-2.5V following stress-relief anneal and complete recrystallization. Alloying additions such as Al to Ti result in significant modification of crystallographic texture and the operating slip systems. Cold working leads to grain-shape anisotropy of the otherwise equiaxed grain structure of Rx materials. The effects of these variables on the deformation microstructures will be investigated along with deformation anisotropy following biaxial loading under varied stress-states and stress-levels. This award will address transitions in creep mechanisms and the effect of underlying deformation mechanism(s) on creep anisotropy. Such studies would be important since 'blind' extrapolation of short-term data to low stresses could lead to 'non-conservative' estimates of creep strains and life of these structural materials in-service. The broader impacts of the proposed study involve significance to technologically relevant structural materials in various industries such as aerospace, chemical, transportation, etc., where the reliability of thin-walled tubing is of great concern during in-service exposure under multiaxial loading. The mechanical anisotropy of these materials, while making it relatively complex in predicting the life of structures, constitutes interesting examples for demonstration for both undergraduate and high school students thereby giving them a good feel for real life problems. While the outcome of the proposed study is of direct relevance to appropriate technologies, the study involves fundamental aspects of mechanical metallurgy and mechanics.