Welding Without Contact: Advancements in Aerospace Welding Technology at BelSU

A team of scientists led by Professor Sergey Mironov, from the Department of Materials Science and Nanotechnology at the Institute of Engineering and Digital Technologies at Belgorod National Research University (BelSU), has made significant improvements to the technology of dissimilar friction stir welding through the implementation of an overlapping weld method.

Friction stir welding (FSW) of aluminium and titanium is frequently utilised in the transport industry, particularly within aerospace applications. The ability to join these two metals facilitates the production of lightweight yet highly durable products and structures. Both materials possess unique properties that render them especially desirable in sectors where minimising weight and ensuring corrosion resistance are critical.

One of the primary challenges associated with FSW is the necessity for expensive working tools, which tend to wear out rapidly when in contact with titanium. The researchers at BelSU have devised a solution: they have developed a technology that allows for welding without direct contact between the tool and the titanium component of the joint.

According to the scientists, during the welding process, a gap of up to 50 micrometres is maintained between the tip of the tool and the interface of the dissimilar aluminium and titanium materials. This approach not only enables the use of more cost-effective working tools but also minimises abrasive wear and prevents damage to the aluminium component from titanium particles.

Moreover, by reducing the temperature during the process, the formation of an undesirable intermetallic layer at the aluminium-titanium interface is significantly slowed down.

“When we eliminate the interaction between the tool and titanium, it considerably lowers the temperature at the boundary of the welded materials. Consequently, we observe a reduction in the thickness of the brittle intermetallic layer, which often leads to cracking. The proposed method not only mitigates crack formation but also substantially enhances the strength characteristics of the weld,” explained Professor Mironov regarding the significance of this new technology.

He further noted that the weld produced using this method exhibits exceptional performance under both quasi-static and fatigue loading conditions.

The joining technique developed by the researchers from Belgorod State University employs an “overlap” scheme, positioning the less durable material (aluminium alloy) at the top of the joint and the more durable material (titanium alloy) below. To generate the necessary heat, a very high angular frequency of rotation (at least 1100 rpm) is used alongside a relatively low feed rate (no more than 75 mm per minute). The tool is inserted solely into the aluminium alloy, ensuring that the distance between its tip and the dissimilar aluminium/titanium interface does not exceed 50 micrometres.