Effect Of Compound Addition Of Nd And Gd On Microstructure,high Temperature Creep And Mechanical Properties Of Mg-6Al Alloy

In this paper,optical microscopy(OM),X-ray diffraction analysis(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and energy spectrum analysis were used to study the effects of the addition of rare earth elements Nd and Gd on the microstructure of Mg-6Al alloy;Mg-6Al-1Nd-xGd(x=0,0.5,1.0,1.5)alloy was subjected to high temperature compression creep test to analyze the composition of each alloy at 150?,175?,200? and 50MPa,70MPa,90MPa under high temperature creep behavior;Mg-6Al-1Nd/0.5Nd-xGd(x=0,0.5,1.0,1.5)alloy high temperature tensile mechanical properties test,The effects of compound addition of Nd and Gd elements and Nd/Gd ratio on the high-temperature tensile mechanical properties of Mg-6Al-1Nd/0.5Nd alloy were analyzed.According to the analysis of the experimental results obtained,the following conclusions can be drawn:1.After the rare earth elements Nd and Gd are added to the Mg-6Al alloy,the Mg-6Al-1Nd-xGd alloy structure consists of four phases:?-Mg phase,?-Mg17Al12 phase and intermetallic compounds Al2Nd and Al2Gd;Mg-6Al-1Nd-0.5Gd alloy Compared with Mg-6Al alloy,the amount of creep strain and steady-state creep rate decreased from 4%and 7.776×10-8s-1 to 2.15%and 2.149×10-8s-1,respectively,decreased of 46.25%and 72.36%.2.Under the condition of 150? and 90MPa stress,the steady-state creep rate of the Mg-6Al-1Nd-xGd(x=0.5,1.0,1.5)alloy gradually decreases with the increase of the Gd content of the rare earth element.When the Gd content is 0.5%and 1.0%,the creep deformation amount and steady-state creep rate of the alloy are 2.20%,2.152×10-8 s-1 and 2.15%,2.149×10-8 s-1,respectively.At 1.5%,it has the lowest creep deformation and steady-state creep rate,which are 1.95%and 1.946×10-8s-1,respectively.The creep constitutive equations of Mg-6Al-1Nd-xGd alloy are:Mg-6Al-1Nd-0.5Gd alloy:?=2.006 × 10-8 ?4.229exp(-107610/RT)Mg-6Al-1Nd-1.0Gd alloy:?=7.714×10-9 ?6.269exp(-74052/RT)Mg-6Al-1Nd-1.5Gd alloy:?=1.877×10-8 ?4.641exp(-73865/RT)3.When the creep temperature of Mg-6Al-1Nd-1.5Gd alloy is increased from 150?to 200?,the steady state creep rate is increased from 1.946×10-8s-1 to 2.128×10-7 s-1.Al2Nd and Al2Gd phases in the structure segregate on the grain boundaries,and the ?-Mg17Al12 phase gradually disperses from a discontinuous network to a block-like distribution after creep at high temperatures;as the creep temperature increases,High,the dislocation lines in the alloy microstructure gradually increase,and obvious slip "steps" and slip lines appear in the grains,which exacerbates the slip deformation of the alloy and makes the creep resistance of the alloy worse.4.After adding rare earth elements Nd and Gd to Mg-6Al-1Nd/0.5Nd alloy,the room temperature and high temperature tensile mechanical properties of the alloy are significantly improved.With the increase of Gd content,the alloy is stretched at room temperature and The tensile strength and elongation under high temperature tensile conditions generally increase first and then decrease;when the total amount of RE(Nd,Gd)in Mg-6Al-1Nd/0.5Nd alloy is 1.5%,Mg-6Al-1Nd-0.5Gd alloy and Mg-6Al-0.5Nd-1.0Gd alloy have excellent high temperature mechanical properties,and the alloy has the best comprehensive mechanical properties when the Nd/Gd ratio is 2:1.