Effect Of Lanthanum Cerium On Microstructure And Properties Of A356 Aluminum Alloy

As new composite materials such as titanium alloys advance,Al-Si alloys need better performance in order to continue to meet industry needs.It has been proved that adding rare earth elements to aluminum alloys can not only refine theα-Al grain,but also improve the coarse needle eutectic silicon.But now most of the rare earths used are pure rare-earth elements,lanthanum-cerium mixed rare-earth is cheaper and more abundant than pure rare-earth elements.KunBased on the study of the modification effect of rare earth elements on aluminum alloys,the mechanical properties and corrosion resistance of the alloys were improved by adding lanthanum-cerium mixture.The effects of lanthanum-cerium mixed rare earth on the microstructure,mechanical properties and corrosion properties of A356 alloy were studied by means of microstructure analysis,tensile test and Na Cl HCl corrosion test.（1）Adding proper rare earth lanthanum cerium to industrial A356 alloy can cause obvious grain refinement.Compared with the unmodified alloy,the addition of mixed rare earth reduced the average grain size and SDAS by 55.76%and 45.89%.The grain size decreases first and then increases with the increase of lanthanum-cerium mixed rare earth addition,and the optimum rare earth addition is 0.4wt%.（2）Compared with the unmodified alloy,the addition of mixed rare earth effectively improves the tensile properties of the alloy.The maximum tensile strength,yield strength and elongation reached 213.2 MPa,159.5 MPa and 3.7%respectively in as-cast state.When the content of lanthanum-cerium mixed rare earth is 0.4 wt%,the maximum tensile strength and elongation are obtained.（3）The rare earth lanthanum cerium mixture can effectively slow down the corrosion rate of the alloy and improve the intergranular corrosion resistance.With the addition of0.0-0.5wt%,the metallographic examination showed that the corrosion surface of A356aluminum alloy changed from a large area to a discontinuous network,and the weightlessness rate decreased from the maximum of 1.3155×10^-4g/（cm²·h）to the minimum of 0.6234×10^-4g/（cm²·h）.The weightlessness rate decreased by 52.61%,and the corrosion resistance of A356 alloy was improved obviously.