挤压温度对固溶态Mg-2.0Zn-0.5Zr-3.0Gd合金微观组织及耐腐蚀性能的影响

Effect of the extrusion temperature on the microstructure and corrosion resistance of solution-treated Mg-2.0Zn-0.5Zr-3.0Gd alloy

摘要:

利用金相显微镜、扫描电镜及透射电镜等测试手段研究了挤压温度对固溶态Mg-2.0Zn-0.5Zr-3.0Gd镁合金显微组织的影响。同时,采用浸泡实验和电化学测试等方法研究了合金在模拟体液中的腐蚀行为。结果表明：挤压态合金主要由大的变形晶粒和动态再结晶晶粒组成,析出相由纳米级的棒状(Mg, Zn)₃Gd相和颗粒状的Mg₂Zn₁₁相组成。挤压温度在340～360 ℃时,合金中动态再结晶晶粒的体积分数随着挤压温度的升高而增加,腐蚀速率随着挤压温度的升高而降低。当挤压温度为360 ℃时,合金发了完全动态再结晶,具有较好的耐腐蚀性,静态腐蚀速率为0.527 mm/y,腐蚀形式为均匀腐蚀。当温度升高至380 ℃时,部分动态再结晶晶粒发生异常长大现象,导致腐蚀速率随着挤压温度的升高而升高。

Abstract:

Effects of the extrusion temperature on the microstructure of solution-treated Mg-2.0Zn-0.5Zr-3.0Gd alloys were investigated by the metallographic microscope, the scanning electron microscope and the transmission electron microscope. Moreover, the mass-loss measurement and electrochemical corrosion technique were used to investigatethe corrosion behaviors of the alloys in the simulated body fluid. The obtained results showed that the extruded alloys were composed of large deformation grains and dynamic recrystallization grains, while the precipitated phases consisted of nanoscale rod-like (Mg, Zn)₃Gd and granular Mg₂Zn₁₁ phase.With an increase of the extrusion temperature in the range of 340 ℃ to 360 ℃, the volume fraction of dynamic recrystallized microstructure of the extruded alloys gradually raised, but the corrosion rates progressively decreased. When the extrusion temperature was 360 ℃, the alloy had a full dynamic recrystallization, and had a better corrosion resistance with a static corrosion rate of 0.527 mm/y, and behaved with a uniform corrosion. When the temperature increased to 380 ℃, a portion of the dynamic recrystallized grains grew abnormally, which resulted in an increase of the corrosion rate with increasing the extrusion temperature.