Авіаційно-космічна техніка та технологія (Aug 2020)
INOCULATION OF ML5 MAGNESIUM ALLOY WITH CARBON NANOPOWDER
Abstract
The development of contemporary aerospace engineering requires consistent improvement of operating characteristics, therefore, the use of advanced light materials becomes more and more urgent. As magnesium alloys are one of the lightest structural materials, their utilization in power plants allows for enhancement of performance characteristics, such as specific power and fuel efficiency. Especially topical is the improvement of the physical and mechanical properties of the magnesium alloys (Mg-Al-Zn system) by controlling their structural characteristics through inoculation. An efficient low-cost grain refinement technique for ML5 magnesium alloy with micro additions of commercially pure carbon nanopowder has been suggested. A comparative metallographic examination of the specimens material with incremental additions of the carbon nanopowder (0.001 %, 0.005 %, 0.01 % 0.05 %, 0.1 % wt.). It has been shown that an optimum addition of the nanopowder in the quantity of 0.005 % wt. contributes to the refinement of the macro- and microstructure and increases a full set of mechanical properties. The addition of the carbon nanosized grain refining agent has also contributed to the refinement of the eutectoid. [δ+γ] phase and the macro grain size have decreased approximately by a factor of 1.5. It has been found that the inoculation of the metal structure is effective within a narrow range of the inoculant concentration in the melt. In particular, the addition of the carbon nanopowder in the quantity of 0.1 % wt. and above led to the formation of internal flaws in the metal – microporosity and film inclusions. The additions of the carbon nanopowder in ML5 alloy have also contributed to the improvement of the ductility properties. In so doing, the addition of 0.005…0.01 % wt. provided for the maximum (approximately two times) increase of the ductility properties and to was some extent beneficial for the tensile strength of the alloy. Further increase of the inoculating agent concentration led to some deterioration of the mechanical properties of the alloy. Thus, the inoculation of the magnesium alloys of Mg-Al-Zn system with micro additions of the carbon nanoparticles is a promising method of improvement of the physical and mechanical properties of cast parts for critical aerospace applications.
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