稀土Nd对喷射沉积高合金化镁合金挤压坯空位浓度影响

Effect of rare earth Nd on vacancy concentration of extruded magnesium alloy by spray deposition

采用喷射沉积技术制备不同Nd含量镁合金沉积坯并进行挤压变形(挤压温度为340℃,挤压比为25∶1),将挤压坯制成φ10×30 mm圆柱试样,最后分别在200,250,300,350,400℃下进行1 h的固溶处理.利用双臂电桥测量了试样的电阻率并计算了合金的空位形成能,利用SEM观察固溶处理后镁合金第二相形貌和分布.结果表明:镁合金挤压坯固溶处理后随温度升高电阻率呈"先升高、后降低"的趋势,350℃以后第二相粒子析出增多,镁合金基体的畸变减小,自由电子的散射强度下降,是电阻率下降的主要原因; Nd固溶到Mg基体后使晶格畸变增加,Mg-Mg键合力减弱,是镁合金挤压坯空位形成能随Nd含量增加而降低的主要原因.

Magnesium alloy billets with different Nd content were prepared by spray deposition and extrusion(the extrusion temperature was 340℃,the extrusion ratio was 25∶1).The extruded billet was made intoφ10×30 mm cylindrical specimen.Finally,the solution was treated at 200,250,300,350,and 400℃for one hour.The resistivity of the alloy was measured by double-arm bridge and the vacancy formation energy of the alloy was calculated.The morphology and distribution of the second phase of magnesium alloy after solution treatment were observed by SEM.The results show that the resistivity of magnesium alloy extruded billet increases first,then decreases with the increase of temperature.After 350℃,the precipitation of the second phase particles increases,and the distortion of magnesium alloy matrix decreases.The main reason for the decrease of resistivity is that the scattering intensity of free electrons decreases.The lattice distortion of Nd solution to Mg matrix increases and the Mg-Mg bond force decreases,which is the main reason why the vacancy formation energy of magnesium alloy extruded billet decreases with the increase of Nd content.