Inspenet, March 17, 2023
Scientists from three institutes of the Siberian branch of the Russian Academy of Sciences have obtained for the first time a welded joint of an aeronautical alloy with the strength of the metal itself, which opens up great prospects in aeronautical engineering in terms of abandoning riveted metal, they said. from the Budker Institute for Nuclear Physics.
The research institute explained that the entire global aviation industry seeks to build stronger aircraft, but at the same time lighter. For this, alloys with improved technical characteristics are being created, such as lithium-aluminum. Such alloys can be welded together without riveting technology, but until recently the big problem was that the weld was not as strong as the alloy itself. The Siberian branch of the Russian Academy of Sciences solved this problem by obtaining for the first time a weld with the same tensile strength as the base material.
The Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences clarified that the low level of resistance of the weld is associated with a change in the structure of the material, which occurs when the metal is rapidly heated by laser radiation and its subsequent transition from a liquid state to a solid state. Using synchrotron radiation, the scientists studied how this structure changes during welding and solved many problems.
“The most advanced lithium-aluminum alloys, such as alloy B-1469, developed at the All-Russian Research Institute of Aviation Materials [VIAM], have a tensile strength of 550 megapascals.[MPa] . If the strength of the specimen with the weld after welding is 300 or 400 MPa, that would be bad. We need the strength level of the weld to be equal to the strength level of the alloy by 100%, and only in this case can we talk about putting the method into practice,” said Alexandr Malikov, head of the Institute’s Laser Technology Laboratory. SA Jristianovich of Theoretical and Applied Mechanics.
The scientist noted that the joint fundamental work made it possible to obtain the strength properties of the seams of all lithium-aluminum alloys, including the aeronautical alloy B-1469, at the strength level of the basic material. In addition, the specialists studied the structural phase state of the weld during laser exposure and understood how the welding process could be controlled.
“When copper and lithium are added, aluminum alloys harden: the added elements disperse in the material, align themselves between the aluminum grains and prevent them from spreading, one could say that they cement them. After obtaining a weld by laser treatment, the reverse process begins in the material —crystallization—, during which the aluminum displaces the reinforcing additives,” explained KonstantÃn Kúper, principal investigator at the Budker Institute for Nuclear Physics.
The scientists selected laser welding temperature regimes in which everything falls back into place, he detailed.
As a result, using special methods of heat treatment, specialists managed to return the metal to the desired phase state and obtain a strong weld.
Photo : © Sputnik / Ilya Naymushin
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