Sr元素对Mg-Zn-Ca合金非晶形成能力和耐蚀性的影响

为改善Mg-Zn-Ca合金的非晶形成能力,采用铜模喷铸法制备了不同Sr含量的Mg-Zn-Ca-Sr合金,其直径为2和4mm棒材试样。利用XRD、SEM、DSC和电化学测试方法研究了Sr元素对Mg-Zn-Ca合金非晶形成能力和在模拟体液中耐蚀性的影响。结果表明,Mg_(65)Zn_(30)Ca_(5-x)Sr_x(x=0,0.5,1.0,1.5,原子分数%,下同)合金直径为2 mm棒材试样组织均为非晶态,而直径为4mm棒材试样均是由非晶和晶体相(Mg和MgZn相)组成,但晶体相的体积分数和尺寸随着Sr元素添加量的增加而减少,即合金的非晶形成能力提高,其中,Mg_(65)Zn_(30)Ca_4Sr_1合金非晶形成能力最强。电化学腐蚀测试结果表明,随着Sr含量增多,合金的腐蚀电位向正向移动,腐蚀电流密度减小,合金的耐蚀性逐渐增强,2 mm棒材试样中Mg_(65)Zn_(30)Ca_(4.5)Sr_(0.5)合金的耐蚀性最好,直径为4 mm棒材试样中Mg_(65)Zn_(30)Ca_4Sr_1合金的耐蚀性最强。

Effect of Sr element on the glass forming ability and corrosion properties of bulk Mg-Zn-Ca alloys

In order to improve the glass forming ability of Mg-Zn-Ca alloy, 2mm and 4mm rod samples of Mg-Zn-Ca-Sr alloys with different amount of Sr were prepared by copper mould injection method. Effects of Sr addition on glass forming ability and corrosion properties in simulated body fluids of Mg-Zn-Ca alloys were studied by means of X-ray diffraction, scanning electron microscopy, differential scanning calorimeter and electrochemical test. Results showed that with the increasing content of Sr element, the 2mm rod samples were all in completely amorphous state. While the microstructure of 4 mm rod samples were composed of amorphous phase and crystalline Mg and MgZn phases. However, the volume fraction and particle size were decreased with increasing addition of Sr element, which indicated that the glass forming ability of Mg-Zn-Ca alloy was enhanced with Sr element addition. Mg65Zn30Ca4Sr1 alloy exhibited the highest glass forming ability. The results of electrochemical test demonstrated that Sr-doped samples showed more positive corrosion potential and smaller corrosion current density, which suggested that the corrosion resistance was improved with increasing addition of Sr element. The corrosion resistance of Mg65Zn30Ca4.5Sr0.5 alloy was the highest among the 2mm rod samples, while the corrosion resistance of Mg65Zn30Ca4Sr1 alloy was the best among the 4mm rod samples.