Comparison of process behavior, microstructure and mechanical properties of ultrasound enhanced friction stir welded titanium/titanium joints

Abstract

Titanium as a high-performance material offers great potential for a wide range of applications with different aspects like lightweight-constructions, biocompatibility as well as design and is used in various industrial areas like the transportation sector or in medical and sports engineering. To exploit the full potential of titanium, there is still a need for innovative and efficient joining techniques compared to conventional methods. The process of friction stir welding as a solid-state joining method is able to produce high-quality similar joints of titanium. Nevertheless, there are still some challenging aspects when friction stir welding titanium like the formation of oxide layers that affect the mechanical properties especially in the field of fatigue negatively. The superposition of power ultrasound on the friction stir welding process can address this issue. Therefore, the hybrid process of ultrasound enhanced friction stir welding was applied on similar Ti6Al4V/Ti6Al4V joints in a butt joint configuration to reduce the amount of oxide layers and improve the fatigue lifetime of the joints. For the joint configuration, a positive impact of the power ultrasound could be identified by the breakup of oxide layers and an increase in the tensile strength of 16%. Also stepwise load increase tests revealed a higher estimated fatigue strength for ultrasound enhanced friction stir welded specimen in this butt joint configuration.

Impact of tool-related parameters during fabrication of dissimilar AISI 1010 – CDA 101 joints by FSW

“…It is a well-known solid state of hot shear technique, which employs a non-exhaustible tool possessing a cylindrical shoulder and unique pin geometry. FSW technique eliminates the various flaws including porosity, solidification based cracking, distortion etc., [33][34][35][36].…”

“…This had resulted in the formation of intermetallic compounds in larger numbers in that zone of stir. These intermetallic compounds are very harder & much sensitive to the formation of cracks, will obviously reduce the strength of the joint [31,36].…”

Current Developments in Friction Stir Welding (FSW) and Friction Stir Spot Welding (FSSW) of Aluminium and Titanium Alloys

“…Titanium alloys are widely utilized in aerospace, rail transportation, and biomedical sectors because of their excellent properties (high strength, high melting point, corrosion resistance), while aluminium alloys also display excellent properties including low density, high strength, and good processability. Furthermore, aluminium alloys are also less costly, while titanium alloys are expensive and have poor processibility that prevents their extensive utilization [21,[37][38][39]. Since the two alloys exhibit different properties including the melting point, thermal conductivity, and linear expansion coefficient, a proper joint configuration is essential.…”

Achieving high property medium-thick Ti/Al dissimilar joints by double side friction stir welding

“…Titanium alloys are widely used in aerospace, rail transportation and biomedical fields due to its high-specific strength, high-temperature performance and corrosion resistance [1, 2]. However, the expensiveness and poor processability of titanium alloy prevents its widespread application.…”