Effects Of Rare Earth Lanthanum And Cerium On The Microstructure And Properties Of 2024 Aluminum Alloy

2024 aluminum alloy is one of the most widely used materials in the field of aerospace,the rapid development of science and technology requires materials with higher strength and excellent comprehensive performance,so the study on the strengthening mechanism of 2024 aluminum alloy is particularly important.The effect that rare earth cerium and lanthanum addition has on the cast microstructure and mechanical properties of 2024 aluminum alloy is investigated.Experimental results indicate that the cerium and lanthanum modified alloys shows refined grains,higher hardness and strength at room temperature,it also improve corrosion resistance of 2024 aluminum alloy.The maximum tensile strength 612 MPa is obtained at the 2024 aluminum alloy with 0.6wt.% cerium(31.9% higher than the unmodified alloy),and the elongation is 16.1%.Compared with the unmodified alloy,the corrosion resistance of 2024 aluminum alloy modified by lanthanum and cerium is improved.And the 2024 aluminum alloy with 0.6wt.% La has the best corrosion resistance.The increased strength and microhardness of the modified alloy are likely result from the following three factors: The rare earth modified alloys have finer grains and ?-Al dendrite,which result in more grain boundaries.The grain boundary could play a role as barrier to the transmission of the dislocations,so the increase in the boundary concentration is helpful for improving the tensile strength.Some aluminum-cerium compounds were founded at the grain boundary and grains.These aluminum-rare earth compounds hindered the dislocation motion and prevented the grain boundary migration or sliding,which demonstrated the tensile strength increased.The surplus blocky aluminum-rare earth compounds had adverse effects on the strength,because where the crack could initiate and propagate easier.The nanometer S precipitated phase in rare earth modified alloys becomes thinner and dispersed,that the movement of dislocation is more hindered.A higher stress needs to be applied to drive the movement of dislocation,that the modified alloys were strengthened.The larger brittle T-phase is prone to fracture and produce crack source under high stress.The reduced T-phase in the modified alloy lowered the unfavorable effect to the alloy,and the modified alloys were strengthened.The rare earth elements can form compounds with impurity elements such as silicon and iron in alloys,which can reduce the electrode potential difference between the compounds and the matrix,also the tendency of pitting.The rare earth can also stabilize and compact the surface structures,and effectively prolongs the corrosion occurrence.The above experimental data provide theoretical research data for the research and development of high-strength and tough 2024 aluminum alloy,and also provide methods for improving the corrosion resistance of 2024 aluminum alloy.