Effect of trace La addition on the microstructure and mechanical property of as-cast ADC12 Al-Alloy

Abstract

The effects of addition of La on the microstructure of as-cast ADC12 Al-Alloy were investigated by using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy disperse spectroscopy (EDS). The experimental results showed that the α-Al and eutectic Si crystals were modified with the addition of 0.3 wt% La. The eutectic Si crystals showed a granular distribution. At the same time, the alloy possessed the best mechanical property. When more than 0.3 wt% La was added to ADC12 aluminum alloy, the microstructure of as-cast alloy was coarsening gradually with the increase of the content of La and the mechanical property decreased. The effect of rare earth La which was added in ADC12 Al-Alloy for up to 0.9 wt% had been investigated in this study. The dendrites of ADC12 Al-alloy was refined obviously and the morphology of Si crystals showed a particle structure when the addition of La reached 0.3 wt%. Besides, the acicular La-rich intermetallics in the alloy deteriorated the mechanical property of alloy. To avoid this unwanted phase, the amount of added rare earth La must be less than 0.6 wt%.

Keywords

as-cast ADC12 Al-Alloy / rare earth / microstructure / intermetallic compound / mechanical property

References

[1] Li R. D., Yu H. P., Yuan X. G. Development and Application of the Diecasting Technology and Alloy [J]. Chinese Journal of Mechanical Engineering, 2003, 39(11): 68-73.

[2] X B Wu, H H Zhang, M M Li, et al. Effects of Iron Phase and Its Aspect on Al-Si Eutectic Alloy[C]. Special Casting & Nonferrous Alloys( Annual Meeting Special Issue), 2006

[3] Rao J., Li H., Wang C., . Study and Application of High Property Die Casting Al Alloy [J]. Journal of Chongqing University(Natural Science Edition), 2005, 28(10): 24-26.

[4] Ma Z., Samuel E., Mohamed A. M. A., . Prameters Controlling the Microstructure of Al-11Si-2.5Cu-Mg Alloys [J]. Materials and Design, 2010, 31: 902-912.

[5] Knuutinen A., Npgita K., McDonald S. D., . Modification of Al-Si Alloys with Ba, Ca, Y and Yb[J]. Journal of Light Metals, 2001, 1: 229-240.

[6] Yuan W. H., liang Z. Y., Zhang C. Y., . Effects of La Addition on the Mechanical Properties and Thermal-resistant Properties of Al-Mg-Si-Zr Alloys Based on AA 6201 [J]. Materials and Design, 2012, 34: 788-792.

[7] Yi H. K., Zhang D., Sakata T., . Microstructures and La-rich Compounds in a Cu-containing Hypereutectic Al-Si Alloy[J]. Journal of Alloys and Compounds, 2003, 354: 159-164.

[8] Yang Y. l. Effects of La on Microstructure and Age-hardening Behabiour of 6061 Alloy [J]. Hot Working Technology, 2009, 38(20): 50-52.

[9] Tsai Y. C., Chou C. Y., Lee S. L., . Effect of Trace La Addition on the Microstructures and Mechanical Properties of A356(Al-7Si-0.35Mg) Aluminum Alloys [J]. Journal of Alloys and Compounds, 2009, 487: 157-162.

[10] Dahle A. K., Nogita K., McDonald S. D., . Eutectic Modification and Microstructure Development in Al-Si Alloys[J]. Materials Science and Engineering A, 2005, 413–414: 243-248.

[11] Kang H. S., Yoon W. Y., Kim K. H., . Effective Parameter for the Selection of Modifying Agent for Al-Si Alloy[J]. Materials Science and Engineering A, 2007, 449–451: 334-337.