Effects Of Nd And T4 Heat Treatment On Microstructure And Mechanical Properties Of AM60 Magnesium Alloy

Because of its low density, high strength, well damping and electromagneti shielding, magnesium alloys were widely used in automotive, electronics, aerospace and other industries. AM series magnesium alloy was used in the automotive industry early. It is necessary to improve the strength and toughness of AM series magnesium alloy to meet the performance requirements of automotive wheels.AM60-xNd alloys were prepared in vacuum resistance furnace and treated at T4 solution in box-type resistance furnace. AM60-0.3Nd alloy was treated at T6 solution. By using Spark atomic emission spectrometer, Plasma spectroscopy, X-ray diffraction, Optical microscopy and SEM, the changes of composition and microstructure were measured. By using Tensile specimen machine and Vickers hardness tester, mechanical properties were measured. Effects of the solution time and Nd on the mechanical properties and microstructure of the AM60-xNd alloys were studied, and its mechanism was discussed. The basic experimental data was provided to develop a new type of high strength and toughness magnesium alloy. The main conclusions as follows: 1)With addition of Nd, the microstructure of AM60-xNd magnesium alloy changed significantly. The size ofα-Mg matrix phase was refined obviously. Theβ-Mg17Al12 phase gradually separated into intermittent and dispersed bone-shaped, tended to become granular. The point-like or block Al11Nd3 phase had the trend of growing and gathering, and the needle or short-stick Al11Nd3 phase had the trend of becoming thicker, longer, and bifurcation .2)After T4 heat treatment, theβ-Mg17Al12 phase decomposed and dissolved into theα-Mg matrix phase. The grain size of alloys was refined obviously and the morphology of Al11Nd3 phase changed largely. Theσb,σ0.2 andδof AM60-0.3Nd alloy can reach to 239Mpa, 138Mpa and 8% respectively. The hardness of AM60-0.6Nd alloy reached 70.5HV. Theσb,σ0.2,δand HV were affected by the sharp and quantity of Al11Nd3 phase.3)After T61 heat treatment,β-Mg17Al12 phase precipitated in the grain boundary. The grain size of AM60-0.3Nd alloy was refined obviously and got to 30μm. The shape and size of Al11Nd3 phase changed significantly, and spherical Al11Nd3 phase changed into lump. The hardness and yield strength increased by 8.7%, 9.2%, tensile strength and elongation rate increased by 23.9%, 33.3%. The tensile strength of AM60-0.3Nd magnesium alloy can reached to 262 MPa.4)The plastic of AM60 alloys was enhanced by adding Nd, because of micro-plastic characteristics appeareding in the fracture and non-basic slip system was activated.The innovation of this study: effects of coagulation with addition of RE and heat treatment on the composition, microstructure and mechanical properties of AM60-xNd alloys were studied, and its mechanism was discussed. developed the AM60 alloy with addition of 0.3% Nd and the best solution treatment process at 410℃×20h .A kind of magnesium alloy is produced ,its strength and toughness are better than the AM60 alloy'.