Effects of Working and Heat Treatment on Microstructural and Mechanical Properties Evolutions in Ti-6Al-4V Fasteners

Titanium fasteners (Ti-6Al-4V) were traditionally used in aircrafts to achieve weight reduction and corrosion resistance. Recently, as the advancement toward composite airplane, the usage of titanium fasteners are increasing, partially due to its excellent compatibility with composite materials, and the microstructure and mechanical properties requirements tend to be more stringent. Thus, knowledge of the relationships between manufacturing processing variables and quality of Ti-6Al-4V fasteners, the microstructure and texture evolution from heading through thread rolling, and the mechanical properties, is crucial for the improvement of the manufacturing process to insure required properties. This evaluation program focuses on the microstructure and mechanical evaluation of Ti-6Al-4V fasteners. The selected fasteners from different stages of manufacturing processing, heading, heat treatment, grinding, and thread rolling, were evaluated by mechanical, microscopy, and X-ray techniques. The primary goal of the microstructure evaluation is to establish control over process variables that affect the quality and integrity of Ti-6Al-4V fasteners using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical properties characterization mainly includes shear testing and compression test at different orientations from as-received wire to fasteners at different strain rates. All these study can give us more comprehensive understanding of Ti-6Al-4V related to the production such as high strain rate deformation mechanism, phase behavior, and microstructural development, setting up a theoretical and experimental basis for extending the use of Ti-6Al-4V into new and innovative applications.