Investigation on Microstructures and Mechanical Properties of the Hypoeutectic Al-10Si-0.8Fe-XEr Alloy

Peng Tang,Kui Huang,Yiyuan Liu,Songyun Deng,Linxin Peng,Huachun Wang,Yanjun Zhao,Zhiliu Hu

doi:10.1155/2020/9147871

Peng Tang, Kui Huang + Show 6 more

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https://doi.org/10.1155/2020/9147871

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Abstract

In this paper, the effect of Er addition (0.2, 0.5, 0.65, 0.8, 1.0, and 1.5 wt. %) on the microstructure evolution and tensile properties of as-cast hypereutectic Al-10Si-0.8Fe alloy was investigated. The phases and their morphologies in these alloys were identified by XRD and SEM equipped with EDX with the help of metallographic analysis techniques; the length of the secondary phase (LSP) and secondary dendrite arm spacing (SDAS) of α-Al grain were quantified. The results indicated that the second phases (primary Si, eutectic Si, and iron-rich phases) and α-Al grain were significantly refined when the addition of Er increased from 0 to 0.8 wt. %. The mean LSP and SADS values were decreased to a minimum value when the Er addition reached 0.8 wt. %. However, the second phases and α-Al grain became coarser when the level of Er increased more than 0.8 wt. %. The analysis of XRD shows that Er mainly exists in the form of Er2Si compound. The microstructure modification also has a significant effect on the mechanical properties of the alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) increase from 52.86 MPa, 163.84 MPa, and 3.45% to 71.01 MPa, 163.84 MPa, and 5.65%, respectively. From the fracture surface, the promotions of mechanical properties are due to the dispersion and pinning reinforcement caused by the Er2Si phase.

Highlights

Al-Si alloys have low density, high strength, and excellent mechanical properties, which are widely used in the aerospace industry, the automotive industry, the construction industry, etc. [1,2,3]
The rare earth element Er can better refine the eutectic silicon in the Al-Si-Fe alloy, and the size of the eutectic silicon can be reduced by 38% when added in an appropriate amount
The Er element added at the same time will generate the Er2Si phase which can be used as heterogeneous nuclei to promote grain refinement

Summary

Introduction

Al-Si alloys have low density, high strength, and excellent mechanical properties, which are widely used in the aerospace industry, the automotive industry, the construction industry, etc. [1,2,3]. Before the addition of a refiner, the second phase in Al-Si alloys is a bulk or plate-like Si phase, and long needle-like β-Fe phase appears when the Fe content increased [10,11,12,13,14] The formation of these phases has an impact on the mechanical properties of aluminum alloys and reduces various mechanical properties. Scanning of the aluminum alloys [17,18,19,20,21], but it has not been proposed which kind of particles the Er element will form with the AlSi alloys to affect the morphology of the secondary phase In this experiment, Al-10Si-0.8Fe will be taken as an object. By means of X-ray diffraction (XRD), scanning electron microscope (SEM)/energy-dispersive Xray spectroscopy (EDX), and tensile fracture morphology, the principle and mechanism of adding the Er element to Al-Si-Fe alloy to enhance its properties were studied

Experimental Materials and Methods

Results

Discussion

Conclusions