Ca对AZ61-1.2Y镁合金组织和力学性能的影响

通过合金制备、微观分析和力学性能测试等方法研究了Ca对AZ61-1.2Y镁合金微观组织和力学性能的影响。结果表明,适量Ca的加入使AZ61-1.2Y镁合金的组织得到明显细化,β(Mg17Al12)相消失,同时析出了高熔点的粒状化合物Al2Y、Al2Ca。合金力学性能的提高,一方面是由于基体晶粒细化产生的细晶强化,另一方面是由于在晶内以及晶界弥散析出的Al2Y和Al2Ca相所产生的析出强化。

Microstructure and Mechanical Properties of Mg-Al-Ca-Nd Alloys Fabricated by Gravity Casting

The aims of this study are to investigate the effects of Nd addition in the Mg-Al-Ca alloys on microstructure and mechanical properties.Microstructure of as-cast Mg-5Al-3Ca alloy containing Nd consists ofα-Mg matrix, eutectic phase and Al-Nd rich intermetallic compound.As Nd addition was increased,α-Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased.Nd addition to Mg-5Al-3Ca based alloys resulted in the formation of Al-Nd rich intermetallic compounds at grain boundary andα-Mg matrix grains.And these Al-Nd rich intermetallic compounds were dispersed homogeneously.In these alloys,two kinds of eutectic phases were observed,i.e.coarse irregular-shape structure at grain boundary and fine needle-shape structure in theα-Mg matrix grain.It is found that the ultimate strength showed the maximum value of 271 MPa at Mg-5Al-3Ca-2Nd alloy and elongation was decreased as the addition of Nd was increased.

析出相对含Ca镁合金腐蚀行为的影响

利用XRD、SEM、TEM和EDS等方法表征了Mg-Al-Zn-XCa(X=0,1.25,1.74,2.53,质量分数,%)合金腐蚀前后的组织结构,并采用失重法、电化学法、扫描探针显微镜(SPM)研究了合金腐蚀行为。结果表明:实验合金主要由α-Mg、β-Mg_(17)Al_(12)、Al_2Ca和(Mg,Al)_2Ca组成。随着Ca含量的增加,合金组织中枝晶臂减小,主要沿晶界分布的Mg_(17)Al_(12)相尺寸、数量逐渐减小,Al_2Ca由骨骼状连接成网状,(Mg,Al)_2Ca增多长大。腐蚀测试结果显示:添加Ca后的合金中α+β共晶相减少,导致腐蚀通道变窄且比例减小。Ca元素能够使阳极自腐蚀电位升高,形成的Al_2Ca阴极相抑制了析氢过程。合金中主要析出相Al_2Ca与α-Mg的电势差小于β-Mg_(17)Al_(12)与α-Mg的电势差。

Al含量对Mg-xAl-2Ca-2Nd合金腐蚀性能的影响

以Mg-xAl-2Ca-2Nd合金为研究对象,通过浸泡实验、电化学分析等方法研究了Al含量对Mg-xAl-2Ca-2Nd合金腐蚀性能的影响。结果表明,随着浸泡时间增加,Mg-Al-Ca-Nd合金浸泡液的pH值增加,当浸泡时间超过40 h时,pH值趋于稳定。随着腐蚀时间增加,Mg-Al-Ca-Nd合金腐蚀速率降低,最终趋于恒定。电化学分析表明,随着Al含量的增加,Mg-Al-Ca-Nd合金的腐蚀电位先增加后降低,腐蚀电流先降低后增加,在Mg-AlCa-Nd合金中,合金耐腐蚀性能先增加后降低。当Al含量为6%(质量分数)和9%时,Mg-Al-Ca-Nd合金耐腐蚀性能最好。腐蚀形貌分析表明,在Mg-Al-Ca-Nd合金中,均以点蚀、局部腐蚀为主。