搅拌摩擦加工调控Mg-5Zn-0.6Zr合金耐蚀性的研究

Research on Regulating Corrosion Resistance of Mg-5Zn-0.6Zr Alloy by Friction Stir Processing

作为一种储量足、比强度和比模量高的轻质结构材料和功能材料,镁的应用前景十分广阔,然而镁的耐蚀性不佳严重限制了其应用范围,较大尺寸的沉淀相导致的电偶腐蚀是镁合金耐蚀性不佳的重要原因。本工作选取铸态Mg-5Zn-0.6Zr合金作为研究对象,对该合金进行了搅拌摩擦加工处理,并对搅拌摩擦加工前后合金的组织结构和电化学性能进行了检测分析。结果表明,搅拌摩擦加工处理后的Mg-5Zn-0.6Zr合金形成了较强的(0001)基面织构,且大部分区域位错密度较低,晶粒尺寸从66.4μm细化到1.6μm,沉淀相发生了一定程度的破碎和弥散分布,在3.5%(下文如无特别说明,均指质量分数)NaCl水溶液中开路电位下的腐蚀电流密度由38.3μA/cm^(2)降至17.0μA/cm^(2),极化电阻由48.98Ω·cm^(2)提升至197.02Ω·cm^(2)。研究表明,搅拌摩擦加工可以有效提高镁合金的耐蚀性。

As a lightweight material with sufficient reserves,high specific strength and specific modulus,the application of magnesium is very promising.The poor corrosion resistance of magnesium seriously limits its application,and galvanic corrosion caused by larger precipitates is an important reason for the poor corrosion resistance of magnesium alloys.In this work,the as-cast Mg-5Zn-0.6Zr alloy was selected as the object of study,and this alloy was friction stir processed.The microstructure and electrochemical properties were examined and analyzed before and after friction stir processing(FSP).The results indicated that after processed by FSP,the Mg-5Zn-0.6Zr alloy exhibited a strong(0001)basal texture with low dislocation density in most regions.The grain size was refined from 66.4μm to the order of 1.6μm,and there was a certain level of fragmentation and dispersed distribution of the precipitates.In a 3.5%(%refers to the mass fraction,if not otherwise stated)NaCl aqueous solution,the corrosion current density decreased from 38.3μA/cm 2 to 17.0μA/cm 2 at open circuit potential.Moreover,the polarization resistance increased from 48.98Ω·cm 2 to 197.02Ω·cm 2.The study indicated that FSP could effectively improve the corrosion resistance of magnesium alloy.