MOSCOW, Russia / EuroWire.IO / – The challenge of joining dissimilar metals has long posed difficulties for engineers, primarily due to the formation of brittle intermetallic layers that weaken welds. These problematic layers tend to crack under stress, compromising the integrity of structures. Recently, a breakthrough in ultrasonic welding technology has been developed to address this issue, significantly enhancing the durability of metal joints. The innovative approach was pioneered by researchers at South Ural State University in Chelyabinsk, in collaboration with colleagues from China. TV BRICS highlighted the findings, citing the university. This new technique is especially effective for joints between metals with different characteristics, such as steel and aluminium.
Creating reliable bonds between dissimilar metals has been a persistent obstacle due to the tendency of brittle intermetallic layers to form at the contact points. These layers are prone to cracking under load, weakening the overall structure. The recent method aims to minimize this risk during spot welding, a process commonly employed to assemble metal sheets in automobiles and other applications. The university announced that the results were published in the journal Engineering Fracture Mechanics.
This technique involves integrating ultrasonic vibrations of approximately 1,200 watts into the welding process. The vibrations facilitate a refinement of the crystal structure within the weld area, reducing crystal size by nearly five times. Instead of coarse grains, the crystals become small and uniformly distributed. Additionally, the process cuts the thickness of brittle intermetallic layers at the joint by 50%, strengthening the weld and reducing the likelihood of failure.
Ultrasound Effectively Eliminates Air Bubbles from Welds
Another benefit of ultrasonic application during welding is its ability to expel air bubbles from the metal. This results in denser welds that contain fewer internal flaws. Testing indicated that the strength of welded joints was doubled when using this method, and the lifespan of the components increased by 1.9 times or 90%. The scientists stated that these enhanced welds are better equipped to withstand prolonged vibration and mechanical stress without developing cracks, which is crucial for parts in moving vehicles.
While the university did not specify exact strength metrics or detailed testing parameters in their announcement, the improvements were described in relative terms. The researchers emphasized that their approach could make structures involving mixed metals more dependable. Combining steel and aluminium is a common strategy to reduce weight while maintaining strength, but weak joints have previously limited such designs. This research was conducted as a collaborative effort with Chinese partners.
Implications for Lighter Vehicles, Aircraft, and Infrastructure
The scientists believe this ultrasonic welding innovation could have broad applications in automotive, aerospace, and construction sectors. In automobiles, the technique could be used to attach steel safety cages to aluminium doors, hoods, and wings. This could lead to lighter hybrid car bodies, enabling electric vehicles to travel further on a single charge. In aerospace, lighter airframes could allow for increased passenger or cargo capacity while reducing fuel consumption. The goal of weight reduction is vital for both industries.
In construction, the method could improve the strength of metal joints in bridges and skyscrapers. The university suggested that such joints might be stronger than traditional monolithic concrete connections. However, the team has not yet indicated a timeline for when this technology might become commercially available. South Ural State University has announced several applied research projects this year, highlighting the potential of this method to produce lighter, more durable structural components.