NOVOSIBIRSK, March 14 Scientists from three scientific institutes of the Siberian Branch of the Russian Academy of Sciences have for the first time obtained a welded seam of an aviation alloy with the strength of the metal itself, which opens up great prospects in the aircraft industry in part of the rejection of metal riveting, the Institute of Nuclear Physics. G. I. Budker SB RAS.
The scientific institute explained that the entire world aircraft industry is striving for the construction of more durable, but at the same time light aircraft. For this, alloys with improved technical characteristics are created, for example, aluminum-lithium. Such alloys can be welded by abandoning the metal riveting technology, but until recently, the big problem was that the weld was inferior in strength to the alloy itself. The Siberian Branch of the Russian Academy of Sciences solved this problem.
«Specialists of the Institute of Theoretical and Applied Mechanics named after S. A. Khristianovich (ITAM SB RAS) together with colleagues from the Institute of Solid State Chemistry and Mechanochemistry of the Siberian Branch The Russian Academy of Sciences (IHTTM SB RAS) and the G. I. Budker Institute of Nuclear Physics SB RAS (BINP SB RAS) have for the first time obtained a weld with the same tensile strength as that of the base material.
The Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences clarified that the low level of strength of the weld is associated with a change in the structure of the material that occurs when the metal is rapidly heated by laser radiation and its subsequent transition from a liquid state back to a solid state. Using synchrotron radiation, scientists have studied how this structure changes during welding and solved many problems.
«The most modern aluminum-lithium alloys, for example, the V-1469 alloy, developed at the All-Russian Research Institute of Aviation Materials (VIAM), have a tensile strength of 550 megapascals (MPa). If the strength of a sample with a seam after welding is 300 or 400 MPa — it will be bad. It is necessary that the strength level of the weld be equal to the strength level of the alloy by 100%, and only in this case we can talk about the introduction of the method into practice, «said Alexander Malikov, head of the laser technology laboratory at ITAM SB RAS.
The scientist noted that the joint fundamental work made it possible to obtain for all aluminum-lithium alloys, including for the aviation alloy V-1469, the strength properties of the seams at the level of the strength of the base material. Moreover, the specialists studied the structural-phase state of the weld during laser exposure and understood how the welding process can be controlled. The studies were carried out at the Siberian Center for Synchrotron and Terahertz Radiation of the INP SB RAS.
«When copper and lithium are added, aluminum alloys are strengthened — the added elements disperse in the material, lining up between aluminum grains, and do not allow them to spread, one might say, they cement them. After using laser exposure, we get a weld , the reverse process begins in the material — crystallization, during which aluminum displaces hardening additives. At ITAM, they selected the temperature regimes of laser welding, in which everything comes back, «explained Konstantin Kuper, senior researcher at the Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences. As a result, using special heat treatment methods, the specialists managed to restore the desired phase state of the metal and obtain a strong weld.