Cailiao Baohu (Oct 2023)
Study on Microstructure Characterization by Laser and CMT-P Arc Hybrid Additive Components
Abstract
In order to clarify the microstructural characteristics of the aluminum alloy additive manufacturing process， the 2024 aluminum alloy commonly used in aircraft structures was used as the research object， and the 2024 high-strength aluminum alloy thin-walled components were successfully prepared using laser and CMT-P arc composite additive manufacturing technology.Using optical microscope，scanning electron microscope， electron probe and other characterization methods， the microstructural characteristics of different areas of the additive components were studied， and their influence law on the microhardness was explored.Results showed that owing to the unique thermal cycling characteristics of the additive manufacturing process， the thin-walled additive parts were formed by a layered structure with alternating three characteristic regions: melt pool boundary (MPB)， melt pool zone (MPZ)， and heat affected zone (HAZ).Among them， the microstructure of MPB was fine equiaxed crystals； the microstructure of MPZ was fine columnar crystals at the bottom， and coarse columnar crystals and equiaxed crystals in the upper part； the microstructure of HAZ was coarse equiaxed crystals.Moreover， the main precipitated phases inside the specimen were S phase (Al2CuMg) and θ phase (Al2Cu)， with the S phase mainly distributed at the intersection of grain boundaries and inside the grains， and θ phase mainly distributed at the grain boundaries.Besides， the microhardness of the interlaminar region inside the additive sample was lower than that of the base material， which might be mainly attributed to the presence of pores between the layers and the presence of more precipitated phases at the grain boundaries.
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