Abstract
The effect of Er addition on the fluidity and microstructure transformation of the as-cast and T5 heat-treated ZL205A alloys was investigated by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The fluidity of the liquid metal after adding Er was tested and the fracture characteristics of the material were analyzed. The results indicated that Er was mainly dissolved into an α–Al matrix near the grain boundaries (GBs). It is easily segregated and enriched in the intersection of the GBs or the interface between the α and θ phase, which caused the intermetallic compounds to be distributed along the GBs to the neck and to fuse. Er could also inhibit the diffusion of Cu atoms in the process of solid solution, so that increased the residual eutectic structures in the crystal, while accelerating the precipitation progress of the Guinier–Preston (GP) zone and θ’ phase and increasing precipitation of the θ phase. A small amount of precipitation of θ phase and micro-scale Er (0.1–0.5 wt %) can significantly increase the fluidity and reduce the casting defects, which can effectively improve the castability of the ZL205A alloy. The interface between the (Al8Cu4Er) phase and matrix is the main area of microcracks, through analyzing the fracture morphology.
Highlights
Aluminum alloy has attracted more and more attention as a kind of dual-use strategy material, due to the good combined properties, such as high strength and toughness, low density, excellent process ability, and good corrosion resistance [1]
To identify the phase components of the samples, a be seen that the dendritic structure of the alloy changes significantly with the different additions of SEMofwith energy dispersive
(1) Micro-scale Er (0.1–0.5 wt %) can significantly increase fluidity and reduce casting defects, which effectively improves the castability of the experimental alloy; (2) Er is mainly a solid dissolved into the matrix phase near the grain boundaries (GBs)
Summary
Aluminum alloy has attracted more and more attention as a kind of dual-use strategy material, due to the good combined properties, such as high strength and toughness, low density, excellent process ability, and good corrosion resistance [1]. Mn addition up to 0.4 wt % forms T (Al12 CuMn2 ) phase with Cu and Al, which is dispersed and strengthened when subjected to solution treatment [5]. Al–Cu–Mn enjoys high specific intensity, excellent processing performance, and good corrosion resistance [6], which is a very important alloy system in material application. Casting defects form under the normal casting conditions, due to a wide range of crystallizing temperature and high hot cracking sensibility, which limits the further application of the alloys in high-performance structure fields [7]
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