RESUMO
Based on the results achieved in systematic studies of structure formation and the formation of multicomponent phases, a scandium-containing filler metal from system alloy Mg-Zr-Nd for welding of aircraft casting was developed. The influence of scandium in magnesium filler alloy on its mechanical and special properties, such as long-term strength at elevated temperatures, was studied by the authors. It is established that modification of the magnesium alloy with scandium in an amount between 0.05 and 0.07% allows a fine-grained structure to be obtained, which increases its plasticity up to 70% and heat resistance up to 1.8 times due to the formation of complex intermetallic phases and the microalloying of the solid solution. Welding of the aircraft castings made of magnesium alloy with scandium-containing filler material allows obtaining a weld with a dense homogeneous fusion zone and the surrounding area without any defects. The developed filler material for welding surface defects (cracks, chips, etc.) formed during operation on aircraft engine bodies makes it possible to restore cast body parts and reuse them. The proposed filler material composition with an improved set of properties for the welding of body castings from Mg-Zr-Nd system alloy for aircraft engines makes it possible to increase their reliability and durability in general, extend the service life of aircraft engines, and obtain a significant economic effect.
RESUMO
The main aim of this work is to improve the structure and properties of the magnesium alloy ML5 by modifying it with alkaline earth metals (ALM). The separate and joint influence of calcium and barium on the macrostructure and microstructure of the alloy of Mg-Al-Zn system was investigated. The qualitative and quantitative estimation of the structural components was carried out. Alkali earth metals were included in complex intermetallic phases and serve as additional crystallization centers. Modification of magnesium alloys with alkaline earth metals is established in an amount of 0.05 to 0.1 wt. % increased the bulk percentage of intermetallic phases by ~1.5 times, shifting them towards smaller size groups while simultaneously forming spherical intermetallic phases located in the grain centre and serving as additional crystallization centers. In this case, grain size reduction and significant refinement of the alloy structural components were provided. The dependency of the separate and joint influence of alkali earth metals on the castings complex of properties of the magnesium alloy has been established. Thus, a separate modification of the ML5 alloy provided the maximum level of its strength and ductility with the addition of 0.1% Ca or Ba. The modification of the complex (0.1% Ca + 0.1% Ba) of the magnesium alloy decreased the dimensions of its structural components 1.5 times and increased the strength of the alloy by 20%, the ductility by 2 times and the long-term heat resistance 1.5 times due to the formation of the intermetallic phases of the complex composition. Linear dependences were obtained that describe the influence of the characteristics of the structural components of the modified magnesium alloy on its mechanical properties. The developed technology for modifying cast magnesium alloys with alkaline earth elements provides an improvement in casting quality and allows the reliability and durability of responsible casting operation.
