Study on Microstructure and Properties of High-Conductivity Die-Cast Al-La Alloys
The effects of La contents(4％,6％,8％,10％)on the microstructures,mechanical properties,thermal and electrical conductivities of die-cast Al-La alloys were investigated.The solid solubility of lanthanum in aluminum matrix was very small,and it was easy to enrich in the front of the solidification interface of α-Al,resulting in component supercooling,reducing the crystallization temperature of the liquid around α-Al,and then inhibiting the growth of α-Al to achieve refinement.The secondary phase Al11La3 produced during solidification process not only improved the strength of the alloy,but also could be used as heterogeneous nucleation point of α-Al to achieve refinement,which was benefit from the small lattice mismatch of 5.96％.With the increase of La content from 4％to 10％,the yield strength and ultimate tensile strength of the alloy increased from 48.6 MPa and 113.9 MPa to 92.3 MPa and 186.7 MPa,respectively,but the elongation decreased from 26.1％to 9.6％.In addition.It was found that the thermal and electrical conductivities decreased linearly with the increase of La content,from 207.8 W/(m·K),32.0 MS/m to 173.1 W/(m·K),26.1 MS/m,respectively.
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