挤压态Mg-2Zn-0.5Gd-1Y-0.5Mn合金的组织特征、力学性能和体外腐蚀行为

Microstructure Characteristics,Mechanical Properties,and In-Vitro Corrosion Behavior of As-Extruded Mg-2Zn-0.5Gd-1Y-0.5Mn Mg Alloys

为改善医用镁合金微观组织特征与降解行为,采用挤压形变工艺改变医用镁合金的晶粒尺寸特征及析出相/金属间化合物尺寸、分布规律,探究了挤压态医用Mg-2Zn-0.5Gd-1Y-0.5Mn镁合金微观结构特征及降解行为。结果表明:不同的热挤压变形并没有改变Mg-2Zn-0.5Gd-1Y-0.5Mn镁合金中第二相的类型,但改变了第二相的分布和形貌。Mg-2Zn-0.5Gd-1Y-0.5Mn镁合金的成分主为α-Mg和W-Mg3Y2Zn3。电化学测试结果表明,铸态、挤压370℃和挤压390℃合金腐蚀电流密度分别为2.498、3.656、1.012μA·cm^(−2)。这是由于铸态组织中析出相/金属间化合物呈带状分布在基体中,可作为微阴极形成电偶腐蚀位点,加速合金腐蚀速率。合金在370℃挤压时,由于实际温度较低,部分粗化相未能充分溶解到α-Mg基体中,随着析出相数量增加及分布混乱无序,微阴极面积比例增大,进而导致腐蚀速率加剧。而390℃挤压态镁合金的挤压速度快、耗散行为慢,且铸锭与挤压机间摩擦强烈,已发生充分动态再结晶行为,降低了微阴极数量/面积,增强了合金耐腐蚀性能。

In order to ameliorate the microstructure characteristics and degradation behavior of the medical Mg alloys,the extrusion process was conducted to change the grain size characteristics and the distribution law of secondary precipitates/intermetallic compounds,and the microstructure characteristics and degradation behavior of as-extruded Mg-2Zn-0.5Gd-1Y-0.5Mn Mg alloy were analyzed.Results show that different hot-extrusion deformation methods do not change the types of the secondary phases in Mg-2Zn-0.5Gd-1Y-0.5Mn Mg alloy,but change their distribution and morphology.The main components of Mg-2Zn-0.5Gd-1Y-0.5Mn Mg alloy areα-Mg and W-Mg3Y2Zn3 phases.The electrochemical tests demonstrate that the corrosion current densities are 2.498,3.656,and 1.012μA·cm^(−2) for as-cast,extruded/370℃,and extruded/390℃Mg alloys,respectively.The precipitates/intermetallic compounds of strip shape are distributed in the matrix of as-cast Mg alloy,which can act as the micro-cathode,thus forming the galvaniccorrosion sites and accelerating the corrosion rates.Partial coarse precipitates cannot completely dissolve into theα-Mg matrix due to the low actual temperature of the Mg alloy during extrusion at 370℃.With the disordered distribution and the increasing precipitates,the area proportion of micro-cathode is increased,which accelerates the corrosion rate.However,for the Mg alloy during extrusion at 390℃,the extrusion speed is fast,the dissipation behavior is slow,and the friction between ingot and extruder is intense,indicating the occurrence of sufficient dynamic recrystallization,which reduces the number/area of micro-cathode and improves the corrosion resistance.