钇对纯镁的组织和性能的影响

采用金相显微镜(OM)、扫描电镜(SEM)对Mg-Y合金与纯镁的铸态凝固组织进行了观察,并采用X射线衍射仪(XRD),能谱分析仪(EDS)对合金在凝固过程中形成的相进行了分析,利用析氢法及电化学方法研究了Mg-Y合金与纯镁在3.5%的NaCl溶液中的腐蚀行为。结果表明,纯镁的晶粒比较粗大,合金的晶粒比纯镁小,合金由灰白色的初生α相和深色的共晶组织构成,以及少量呈颗粒状弥散分布在基体中Mg24Y5相。析氢法中,试样在浸泡了8 h左右时,合金腐蚀速率是纯镁的2.85倍,纯镁在浸泡7 h后pH值稳到10.4左右,而合金的pH值变化较快,在1.5 h后就已经达到了10.4,最后稳定在11.2左右。从腐蚀形貌看,纯镁的腐蚀较浅,沿表面扩展,呈纹理状,合金则呈现明显的局部腐蚀特征,表面形成了严重的腐蚀坑。3.5%的NaCl溶液中测得的极化曲线可以得出,合金的腐蚀电流Icorr(4.05×10-4A.cm-2)比纯镁Icorr(6.81×10-5 A.cm-2)要高的多。

Effect of Yttrium on Microstructure and Property of Pure Magnesium

Solidification structure of cast was studied by using optical microscopy(OM),scanning electron microscopy(SEM).X-ray diffractometry(XRD) and energy disperse spectroscopy(EDS) to analysis the phase formed in solidification of pure magnesium and Mg-Y alloy.Hydrogen evolution experiment and polarization curves were used to analysis the corrosion behavior of pure magnesium and Mg-Y alloy in 3.5% NaCl solution.The results showed that the grain size of pure magnesium was coarser than that of Mg-Y alloy.The alloy was composed of primary α phase,eutectic microstructures as well as a little Mg24Y5 distributed on the matrix as particles.When immersed in 3.5% NaCl solution for 8 h,the corrosion rate of Mg-Y alloy was 2.85 times of pure magnesium in hydrogen evolution experiment.pH was about 10.4 after soaked for 7 h for pure magnesium.But pH of the alloy varied quickly.It was about 10.4 after 1.5 h and finally it was stabled at 11.2.The corrosion degree of pure magnesium was very shallow by corrosion morphology and the corrosion route was extended along the surface in texture-like shape.While the Mg-Y alloy was major local corrosion and there were serious corrosion pits on the surface.