Effect Of Nd Content On Microstructure And Mechanical Properties Of Mg-9Gd Alloy

As a lightweight material,magnesium alloy has outstanding development prospects,but its low strength at room temperature and high temperature cannot meet the requirements for use in aerospace and military fields;and Mg-Gd-Nd(heavy-light double rare earth)Magnesium alloys not only have excellent room temperature and high temperature performance,but also can reduce the density and cost of the alloys.In this paper,Mg-9Gd-0.5Zr is selected as the matrix alloy,and Mg-9Gd-x Nd-0.5Zr(x=0 wt.%,0.5 wt.%,1.0 wt.%,1.5wt..%,2.0wt.%,2.5 wt.%)Alloy.By means of OM,SEM,EDS,XRD,FIB,etc.,the influence of different Nd contents on the microstructure and mechanical properties of as-cast,solid-solution,and extruded Mg-9Gd-0.5Zr alloys is mainly studied,the creep behavior of extruded Mg-9Gd-2.0Nd-0.5Zr alloy was also investigated.The results show that after adding Nd element to the as-cast Mg-9Gd-0.5Zr alloys,the grains can be significantly refined,and the grain size decreases with the increase of Nd content.When the Nd content is 2.0 wt.%,its grain size reaches a minimum of 30.3?m.The as-cast Mg-9Gd-0.5Zr alloy structure consists of an?-Mg matrix,a block-shaped Gd-rich phase,and irregular stripes Mg₅Gd phase.As the Nd content increases,the number of Mg₅Gd phases continues to decrease,and the number and size of newly generated skeletal Mg₅Gd_0.6Nd_0.4phases are increasing.The grain size of the solid solution alloy is consistent with the as-cast condition.Under the same solid solution conditions,as the Nd content increases,the number of second phases dissolved in the matrix of Mg-9Gd-x Nd-0.5Zr alloys gradually increased.When the Nd content is 2.0wt.%,besides the high melting point and high hardness of the block-shaped Gd-rich phase in the alloy matrix,the alloy almost reach complete solid solution.After dynamic recrystallization of the extruded alloys,their grains are significantly refined,as the Nd content increases,their grain size continues to decrease.When the Nd content is 2.0 wt.%,its grain size reaches a minimum of1.27?m,and the number of precipitated phases in its structure also reaches a peak,which can effectively promote recrystallization proceeds,and the combined effect of fine-grain strengthening and second-phase strengthening increases its room-temperature tensile strength and plasticity at the same time,and its yield strength,ultimate tensile strength,and elongation reach 304 MPa,372 MPa,and 31.1%.Extruded Mg-9Gd-2.0Nd-0.5Zr alloy,with the increase of creep temperature and applied stress,the steady-state creep rate increases significantly,resulting in shortened creep life,the creep stress index of the alloy The value of n is between 3 and 5,the value of creep activation energy Q It is76.1?136.2 KJ/mol,and its creep mechanism is dislocation climbing+slip mechanism(Climb-plus-glide),and it is mainly controlled by dislocation climbing.