Study On The Microstructure And Properties Of New Type Zn-Al-Cu-Mg-La-Ce Alloy

Zinc-aluminium alloy has many advantages,such as low melting point,good casting performance and low cost,which can be used in automobile,ship,arts and crafts,and building materials.However,its low mechanical properties,plasticity and toughness limit its application field and service life.Lanthanum(La)and Cerium(Ce)rare earth elements have active chemical properties and strong modification ability for zinc-aluminium alloy.Therefore,the researches on improving the structure and mechanical properties of zinc-aluminium alloy by La and Ce rare earth elements have been carried out.However,the effects of single La or Ce rare earth element on improving the structure and mechanical properties of zinc-aluminium alloy are limited and not obvious.Therefore,it is of great significance to further study the ways and mechanisms of improving the structure and properties of zinc-aluminium alloy by rare earth elements.In order to improve the structure and mechanical properties of zinc-aluminium alloys,different components of Zn-Al-Cu-Mg-La-Ce alloys were designed and prepared by stirring casting method via adding La and Ce separately and jointly.Through comparative analysis of their microstructures and mechanical properties,the effects of La/Ce ratio and the total amount of La+Ce on the microstructure and mechanical properties of Zn-Al-Cu-Mg alloy were investigated,as well as the influence mechanism of La and Ce.The results of La/Ce ratio study show that simple La or Ce has a certain effect of fine grain strengthening on zinc-aluminium alloys.Comparatively,adding La and Ce jointly present a stronger effect of fine grain strengthening on zinc-aluminium alloy,and can significantly improve the microstructure and mechanical properties.With the increase of La/Ce ratio,the size of ?-Zn phase decreases gradually,the proportion of eutectic structure increases gradually,and the mechanical properties and wear resistance increase gradually.When La/Ce=2 and adding 0.2wt.% La and 0.1wt.% Ce,the microstructure and mechanical properties of zinc-aluminium alloy are better,the granular ?-Zn phase is fine and uniformly distributed,and the reticular eutectic structure is distributed throughout the microstructure.The brinell hardness,tensile strength and compressive strength at 20% compressive strain are HB128,330 MPa and 571 MPa,respectively,higher than those of the zinc-aluminium alloy without La and Ce by 20.8%?20.0% and 12.0%,respectively.The wear rate is 0.79%,lower than that of the zinc-aluminium alloy without La and Ce by 63.8%.In case of La/Ce=2,the research results of jointly adding La and Ce show that,with the increase of the total amount of La+Ce,The microstructure of the alloys were refined first and then coarsened,and the mechanical properties and wear resistance increased first and then decreased.When jointly adding 0.3wt.%(La+Ce),the mechanical properties and wear resistance of the zinc-aluminium alloy are better than those of the zinc-aluminium alloys with 0.15 wt.% and 0.6wt.%(La+Ce).The brinell hardness,tensile strength and compressive strength at 20% compressive strain of the zinc-aluminium alloy are higher than those of the zinc-aluminium alloy with 0.15 wt.%(La+Ce)by 6.7%,12.2% and 5.2%,respectively,and the wear rate is lower than that of the zinc-aluminium alloy with 0.15 wt.%(La+Ce)by 44.8%.The brinell hardness,tensile strength and compressive strength at 20% compressive strain are higher than those of the alloy with 0.6wt.%(La+Ce)by 9.4%,13.8% and 5.7%,respectively,and the wear rate is lower than that of the zinc-aluminium alloy with 0.6wt.%(La+Ce)by 46.3%.