Mg67Zn28Ca5合金激光表面熔凝处理及其生物腐蚀性能

镁锌钙合金因为具有较高的比强度和优异的可降解性,有望成为新一代的内固定材料,但是镁合金耐生理腐蚀能力相对较差而限制了其临床应用。通过激光熔凝处理对共晶成分的Mg67Zn28Ca5合金进行了表面改性,研究了Mg67Zn28Ca5合金激光熔凝处理前后的显微组织、相结构和元素分布;以及在人工模拟体液中合金激光熔凝处理前后的生物腐蚀性能。研究结果表明,Mg67Zn28Ca5合金经过激光熔凝处理后,在合金的表层形成了平均厚度约508.1 μm的熔凝层,该熔凝层平均晶粒大小约10 μm。与铸态和固溶态的合金相比,熔凝层在人工模拟体液中的腐蚀电位分别正移了76 mV和60 mV;熔凝层的腐蚀速率分别降低了82%和78%,为0.0468 mm/a。经激光熔凝处理后,合金表面的氧化膜也更为致密,提高了镁合金的耐腐蚀性能。MgZn2相含量减少和第二相尺寸的减小,降低了电偶腐蚀的程度,抑制了α-Mg基体相的腐蚀。     

Mg-Zn-Ca表面微弧氧化涂层的制备及耐蚀性能研究

目的 提高Mg-Zn-Ca的耐腐蚀性能.方法 在Na2HPO4、NaOH和C3H8O3溶液中,采用微弧氧化(MAO)技术在Mg-Zn-Ca表面通过调节电参数中正向占空比的大小(20％、30％和40％)制备耐蚀性能涂层.利用XRD和SEM表征涂层的物相和形貌.采用光学显微镜测量涂层厚度.采用划痕仪测试涂层与基体的结合力.采用电化学工作站测试涂层的耐腐蚀性能.结果 XRD结果表明,涂层物相主要为MgO、Mg3(PO4)2、ZnO和Zn3(PO4)2.随正向占空比的增加,当2θ角为32.4°、37.2°、43.1°、62.8°时,同一物相对应的衍射峰强度越来越低.SEM结果显示,随正占空比的增加,涂层孔径增大,表面颗粒状涂层产物直径变大.正占空比为20％时,涂层的致密性最好.划痕仪测试结果显示,正占空比为20％时,涂层与基体的结合强度最大,为61.70 MPa.涂层厚度测试表明,正占空比为40％时,涂层最厚,为15.89μm.电化学测试结果表明,正占空比为30％时,涂层的阻抗值最大(490.41?),腐蚀电位最高(–1.16 V),腐蚀电流较小(4.9×10–5 A/cm2).Mg-Zn-Ca涂层材料在3.5％的NaCl溶液中的极化形式以电化学极化为主.结论 采用微弧氧化方法在Mg-Zn-Ca表面制备了耐蚀涂层,当电参数中正向占空比由20％增加到30％时,涂层的耐蚀性能提高,但占空比继续增大到40％时会导致涂层孔径和孔隙率过大,材料的耐蚀性能反而降低.     

Ca及其含量对快速凝固Mg-Zn合金组织和性能的影响

采用雾化-双辊急冷法成功制备了快速凝固（RS）Mg-Zn-Ca合金薄片,分析了不同含量的Ca对RS Mg-Zn合金微观组织、物相种类和热稳定性的影响。结果表明,RS Mg-6Zn合金的组织细小,晶粒尺寸为6～10μm,其相组成为α-Mg、Mg51Zn20相及少量的MgZn2和Mg2Zn3相。随着Ca的加入及其含量的增加,合金的组织显著细化（达到3～5μm）、析出相的数量大幅度增加,同时低熔点的Mg51Zn20相逐渐被大量热稳定的Ca2Mg6Zn3和Mg2Ca相替代,有效地阻碍了高温下晶界的运动,从而有助于合金组织热稳定性的提高;其中,RS Mg-6Zn-5Ca合金最为显著。     

Homogeneous corrosion of high pressure torsion treated Mg-Zn-Ca alloy in simulated body fluid

Magnesium alloys have got extensive attention as biodegradable implant materials due to their biodegradability in the physiological environment and similar elastic modulus to natural bone. But their poor corrosion resistance is a dominant problem that limits their clinical application due to the inhomogeneous distribution of the second phase. Nevertheless, after high pressure torsion (HPT) treatment, the second phase became nano-sized particles and distributed uniformly in grain interiors instead of along grain boundaries. The immersion tests indicated that the HPT-treated sample exhibited homogeneous corrosion resulting from the uniform distribution of the second phase. The results of the potentiodynamic polarization experiments showed that, compared with the as-cast alloy, the corrosion current density of the HPT-treated alloy decreased from 5.3 × 10^− 4 A/cm² to 3.3 × 10^− 6 A/cm².     

Effects of Zinc and Calcium Concentration on the Microstructure and Mechanical Properties of Hot-Rolled Mg–Zn–Ca Sheets

Four kinds of Mg alloys with different Zn and Ca concentration were selected to analyze the effect of Zn and Ca concentration on the microstructure and the mechanical properties of Mg–Zn–Ca alloys. It was found that Zn and Ca concentration has a great influence on the volume fraction, the morphology and the size of second phase. The Mg–1.95Zn–0.75Ca(wt%) alloy with the highest volume fraction, continuous network and largest size of Ca2Mg6Zn3 phase showed the lowest elongation to failure of about 7%, while the Mg–0.73Zn–0.12Ca(wt%) alloy with the lowest volume fraction and smallest size of Ca2Mg6Zn3 phase showed the highest elongation to failure of about 37%. It was suggested that uniform elongations of the Mg–Zn–Ca alloys were sensitive to the volume fraction of the Ca2Mg6Zn3 phases, especially the network Ca2Mg6Zn3phases; post-uniform elongations were dependent on the size of the Ca2Mg6Zn3 phase, especially the size of network Ca2Mg6Zn3 phase. Reduction in Zn and Ca concentration was an effective way to improve the roomtemperature ductility of weak textured Mg–Zn–Ca alloys.     

Electrochemical Hydrogen Storage Characteristics of the as-Cast and Annealed La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0~0.4) Electrode Alloys

研究了Mg-3.8Zn-2.2Ca-xSn(x=0,0.5,1,2,质量分数%)镁合金的铸态组织、抗拉性能和蠕变性能。结果发现:在含Sn合金中会形成CaMgSn相,并且随着Sn含量从0.46%增加到1.88%(质量分数),合金中CaMgSn相的数量增加。同时,合金中Ca2Mg6Zn3相的形貌从最初的连续和/或半连续网状转变为半连续和/或断续状。此外,含Sn合金的晶粒被明显细化,其中含0.90%Sn合金的晶粒最细。与三元合金相比,含0.46%和0.90%Sn合金的抗拉性能和蠕变性能改善明显,而含1.88%Sn合金的屈服强度和蠕变性能虽然得到改善,但其抗拉强度和延伸率减小。在含0.46%、0.90%和1.88%Sn的3个合金中,含0.90%Sn的合金显示了优化的抗拉性能和蠕变性能。     

Dominant Deformation Mechanisms in Mg-Zn-Ca Alloy

The coaddition of Zn and Ca has great potential to improve the ductility of Mg alloys. Herein, the mechanical properties of an extruded Mg-Zn-Ca solid-solution alloy were studied by quasi-in situ electron backscatter diffraction (EBSD)-assisted slip trace analysis. The dominant deformation mechanisms of the Mg-Zn-Ca alloy were studied, and the origins of enhanced ductility were systematically revealed. The results indicate that most grains deformed by basal slip. In addition, multiple non-basal slip traces were detected (particularly prismatic, pyramidal I <  a > , and pyramidal I <  c +  a > slip traces), and their activation frequency was promoted with increasing tensile strain. The enhanced participation of non-basal slip systems is believed to play a critical role in achieving homogeneous plastic deformation, thus effectively promoting the ductility of the Mg-Zn-Ca alloy. Furthermore, first-principle calculations revealed that the coaddition of Zn and Ca significantly reduces the unstable stacking fault energy for non-basal slip, which contributes to the activation of non-basal slip systems during plastic deformation.     

医用Mg-Zn-Ca合金在模拟体液中的腐蚀行为

利用铸造技术制备不同成分的医用Mg-Zn-Ca合金,在470℃对部分合金进行24 h的固溶处理.测试合金在模拟体液中的腐蚀行为.结果表明,合金经过固溶处理后其在模拟体液(hank's)中的电化学自腐蚀电位均出现正偏移现象,耐浸泡腐蚀性能也有较大的提高.在模拟体液中,未经固溶处理合金中的最大腐蚀速率达到5.3265 mm/a,经过固溶处理后合金的最大腐蚀速率降低到0.8632 mm/a.说明固溶处理后合金具有较好的耐腐蚀性能.     

Mg-Zn-Ca合金的非晶形成能力及力学性能

利用铜模铸造制备直径为1~4 mm的Mg72-xZn28Cax(x=1~6)合金,采用XRD、DSC、SEM和力学性能试验机分别对合金的非晶形成能力、相组成、断口形貌和力学性能进行研究。结果表明:在x为3、4和5时,Mg72-xZn28Cax合金的非晶形成能力(以直径表示)分别为2、3和2 mm;而当x为1、2和6时,Mg72-xZn28Cax合金的非晶形成能力低于直径为2 mm的;当x为3和5时,直径为2 mm的非晶态合金的屈服强度分别为591 MPa和662 MPa,塑性变形量分别为0.5%和0.2%;直径为3、2和1 mm的Mg68Zn28Ca4非晶合金的屈服强度分别为540、611和610 MPa,塑性变形量分别为0.48%、1.28%和6.2%,Mg68Zn28Ca4非晶合金是目前所报道的塑性变形量最大的镁基非晶合金;单位剪切面上弹性能的减少及其分布均匀性的改善是样品尺寸减小促使塑性应变量提高的主要原因。     

Mg-Zn-Ca系富Mg侧三元化合物及其300℃固态相平衡

采用合金平衡组织结构分析法,利用扫描电镜组织观察、电子探针定量成分分析以及X射线衍射和透射电子衍射结构分析,对Mg-Zn-Ca系富Mg区域300°C的相平衡关系及平衡相成分进行研究。结果表明：300°C时,2个三元化合物T1和T2都可与Mg基固溶体相平衡。T1相是一个线性化合物相,成分为15%Ca（摩尔分数）,20.5%～48.9%Zn,余量为Mg。T1相为六方晶体结构,晶格常数为：a=0.992～0.945nm,c=1.034～1.003nm,随T1相中Zn含量的增加而减少。化合物T2相也是六方结构,成分为26.4%～28.4%Mg,63.2%～65.5%Zn以及7.1%～8.4%Ca。300°C时,Zn在Mg基固溶体中的溶解度随Ca的加入而增大,最大溶解度达到3.7%。在Mg-Zn-Ca系中300°C等温截面相图的富Mg区域存在着三相区α-Mg＋Mg2Ca＋T1,α-Mg＋T1＋T2,α-Mg＋T2＋MgZn和MgZn＋T2＋Mg2Zn3。