Mg-Zn-Ca合金的体外降解行为

背景:鉴于人体复杂的生理环境,目前降解实验中使用的模拟生理体液种类繁多,因此分析Mg-Zn-Ca合金在不同模拟体液中的降解行为具有重要意义。目的:研究Mg-Zn-Ca合金在不同模拟体液中的降解过程和性能变化,明确Ca含量和模拟体液种类对合金的影响。方法:采用熔融挤压成型工艺制备含钙质量分数分别为0.2%,0.5%,1%的Mg-Zn-Ca合金,依次命名为Mg-Zn-0.2Ca、Mg-Zn-0.5Ca、Mg-Zn-1Ca合金,以Mg-Zn合金作为对照。将每种合金分别置于3种模拟体液(生理盐水、PBS和Hank’s液)中,对合金降解过程中的形貌、成分变化、质量损失、pH值及力学性能等进行表征分析。结果与结论:①随着降解时间的延长,4种合金表面生成了大量的纳米级片层和柱状结构,主要成分是MgO和Mg(OH)2,4种合金在生理盐水中的降解速度最快,在Hank’s液中的降解速率最慢,在生理盐水中的降解速率快慢为:Mg-Zn<Mg-Zn-0.2Ca<Mg-Zn-0.5Ca<Mg-Zn-1Ca,在PBS和Hank’s液中的降解速率快慢为:Mg-Zn<Mg-Zn-0.2Ca≈Mg-Zn-0.5Ca<Mg-Zn-1Ca;②随着降解时间的延长,4种合金都有一定的质量损失,其中在生理盐水中降解最快,在Hank’s液和PBS中降解缓慢,并且在相同模拟体液中,随着合金中钙含量的增加,合金的腐蚀速率明显加快;③4种合金降解环境pH值的上升主要集中在1 d内,之后趋缓,在PBS中的pH值上升幅度较其他两种模拟体液大,并且在相同模拟体液中,随着合金中钙含量的增加,降解环境pH值上升显著;④在初始状态下,各Mg-Zn-Ca合金的弹性模量均高于Mg-Zn合金;置于模拟体液中后,随着降解时间的延长,4种合金的弹性模量均有所降低,其中在生理盐水中降低最明显;⑤结果显示,Ca加入改善了Mg-Zn合金的力学性能,少量Ca不会加快合金的降解速率,但过量Ca加快了合金的降解速率,降解过程中生理盐水模拟体液对合金力学强度的影响最显著。

挤压工艺对Mg-Al-Ca-Zn合金组织与性能的影响

对Mg-2.0Al-1.5Ca-0.8Zn合金进行了320~400℃,32、64不同挤压比的挤压试验,采用OM、SEM、拉伸试验、腐蚀试验等手段,研究了不同挤压工艺对Mg-2.0Al-1.5Ca-0.8Zn合金组织与性能的影响。结果表明:随着挤压温度和挤压比的升高,合金的晶粒尺寸逐渐增大。随着挤压温度的升高,合金的抗拉强度逐渐提高,伸长率和耐腐蚀性先升高后降低。挤压温度400℃,挤压比32时挤压的合金的抗拉强度最高,为268.5 MPa。挤压温度360℃,挤压比64时挤压的合金的塑性最佳,其伸长率为27.4%。挤压温度360℃,挤压比32时挤压的合金的耐腐蚀性最好,其腐蚀失重率为226.4 mg/(cm^(2)·h)。

Microstructure,mechanical properties and corrosion behavior of quaternary Mg−1Zn−0.2Ca−xAg alloy wires applied as degradable anastomotic nails

The microstructure,mechanical properties and corrosion behavior of quaternary degradable Mg−1Zn−0.2Ca−xAg(x=1,2,4 wt.%)alloy wires,intended as anastomotic nails,were investigated.It was found that these Ag-containing alloy wires mainly consist of Mg matrix and Ag17Mg54 phase,characterized by SEM,EDS,XRD and TEM.Tensile and knotting tests results demonstrate the superior mechanical properties of these alloy wires.Especially,Mg−1Zn−0.2Ca−4Ag alloy exhibits the highest mechanical properties,i.e.an ultimate tensile strength of 334 MPa and an elongation of 8.6%.Moreover,with increasing Ag content,the corrosion rates of these alloy wires remarkably increase due to the formation of more micro-galvanic coupling between Mg matrix and Ag17Mg54 phase,shown by mass loss and scanning Kelvin probe force microscopy(SKPFM)results.The present alloy can be completely degraded within 28 d,satisfying the property requirements of anastomotic nails.

Microstructure of Mg-8Zn-4Al-1Ca aged alloy

The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.

不同预时效挤压态Mg−Gd−Y−Zn−Zr合金的再结晶行为和强化机制

通过控制预时效时间制备3种不同状态的试样,研究不同预时效状态对挤压态Mg−9.5Gd−4Y−2.2Zn−0.5Zr(质量分数,%)合金的动态再结晶行为(DRX)和性能的影响。结果表明,欠时效挤压(UAE)样品的细晶体积分数为17.4%,而峰时效挤压(PAE)和过时效挤压(OAE)样品的细晶体积分数分别达到89.7%和50.4%。在晶粒内部和晶界处分布的致密、细小的β颗粒相通过粒子激发形核机制显著提高了形核位点和位错密度。然而,致密针状γ'相抑制位错滑移,延迟DRX形核。PEA和OAE样品中细小晶粒的差异归因于原始颗粒相的数量和尺寸的不同,而其拉伸性能的差异归因于不同的显微组织。由于晶界强化和析出强化机制的贡献更大,PAE样品具有更优异的拉伸性能。

Investigation on microstructures and mechanical properties of Mg-6Zn-0.5Ce-xMn(x=0 and 1)wrought magnesium alloys

The microstructure evolution and mechanical properties of Mg–6Zn–0.5Ce–xMn(x=0 and 1 wt.%)wrought magnesium alloys were researched,and the morphologies and role of Mn element in the experimental alloys were analyzed.The research shows that all of Mn elements form theα-Mn pure phases,which do not participate in the formation of other phases,such as theτ-phases.The mechanical properties of Mn-containing alloys in as-extruded and aged states are superior to Mn-free alloys.During the hot extrusion process,the dispersed fineα-Mn particle phase hinders the migration of grain boundaries and inhibits dynamic recrystallization,which mainly takes effect of grain refining and dispersion hardening.During the aging treatments,the dispersed fineα-Mn particle phase not only hinders the growth of the solution-treated grains,but also becomes the nucleation cores ofβ1 rod-like precipitate phase,which is conducive to increasing the nucleation rate of the precipitate phase.For the aged alloy,the Mn addition mainly takes effect of grain refining and promoting aging strengthening.

Microstructure and mechanical properties of squeeze-cast Al−5.0Mg−3.0Zn−1.0Cu alloys in solution-treated and aged conditions

The microstructure and mechanical properties at different depths of squeeze-cast,solution-treated and aged Al−5.0Mg−3.0Zn−1.0Cu alloy were investigated.For squeeze-cast alloy,from casting surface to interior,the grain size ofα(Al)matrix and width of T-Mg32(AlZnCu)49 phase increase significantly,while the volume fraction of T phase decreases.The related mechanical properties including ultimate tensile strength(UTS)and elongation decrease from 243.7 MPa and 2.3%to 217.9 MPa and 1.4%,respectively.After solution treatment at 470℃ for 36 h,T phase is dissolved into matrix,and the grain size increases so that the UTS and elongation from surface to interior are respectively reduced from 387.8 MPa and 18.6%to 348.9 MPa and 13.9%.After further peak-aging at 120℃ for 24 h,numerous G.P.II zone andη′phase precipitate in matrix.Consequently,UTS values of the surface and interior increase to 449.5 and 421.4 MPa,while elongation values decrease to 12.5%and 8.1%,respectively.

Fine Scale Precipitates in Al-Mg-Zn Alloys after Various Aging Temperatures

This article deals with investigation of fine-scale precipitation in Al-Mg-Zn alloys with compositions of Al - 2 at% Mg- x at% Zn, (x = 1.8, 2 and 4.2). The precipitates morphology was examined by scanning electron microscope (SEM) and correlated with the microhardness (HV) and differential scanning calorimetry (DSC) of the specimens. The precipitates are characterized as h’ (MgZn2) and h (MgZn2) phases of hexagonal structure of the same composition with a slight difference in lattice parameters. In addition, T-phase pf composition (Mg32 (Al, Zn)49) having a cubic crystal structure. Owing to the determined activation energies of the precipitates, the kinetics associated with their nucleation and growth can be characterized. The thermal energy acquired during aging leads to the agglomeration of precipitates to or larger particle sizes.

Effect of Pre-Aging, Over-Aging and Re-Aging on Exfoliation Corrosion and Electrochemical Corrosion Behavior of Al-Zn-Mg-Cu Alloys

By means of TEM, hardness, conductivity, tensile strength test, fracture toughness test, polarization curve and EIS, the Al-Zn-Mg-Cu alloys treated by a new multi-stage aging system, i.e. pre-aging, over-aging and re-aging (120&#176;C/24h + 160&#176;C/8h + 120&#176;C/24h), were characterized. It is found that compared with the Al-Zn-Mg-Cu alloys treated by T76 (120&#176;C/24h + 160&#176;C/8h), the new multi-stage aging treatment can improve the tensile strength, fracture toughness, hardness and conductivity of the alloys at the same time. This is mainly due to the pre-aging, over-aging and re-aging process of super high strength aluminum alloys. Compared with the two-stage over aging process, the formation of multi-stage multi-phase precipitation structure can improve the strength, toughness and corrosion resistance of the alloys at the same time. The polarization curve is consistent with the conclusion. Therefore, we conducted this study to test how the comprehensive properties of the alloy can be improved.

Microstructure and mechanical properties of Mg_(94)Zn_2Y_4 extruded alloy with long-period stacking ordered structure

The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.

晶粒尺寸对生物医用Mg-3Zn-0.2Ca-0.2Mn合金降解行为的影响

本文通过固溶工艺调控,获得第二相含量相近、晶粒尺寸不同的Mg-3Zn-0.2Ca-0.2Mn合金,对具有不同晶粒尺寸的合金在Hank’s模拟体液中进行浸泡及电化学实验,通过观察降解后的合金形貌,研究并分析了晶粒尺寸对生物医用Mg-3Zn-0.2Ca-0.2Mn合金降解行为的影响。通过电化学实验可知,合金晶粒尺寸越小,腐蚀电流密度越小,阻抗值越大;通过浸泡实验及对合金表面形貌的观察可知,随着晶粒尺寸的减小,合金降解速率减慢,表面腐蚀坑尺寸越小且分布越均匀,合金的耐蚀性越好。合金降解过程中晶粒尺寸是通过影响合金降解产物膜的致密度及完整性,进而影响合金的耐蚀性能,即合金的晶粒尺寸越小,表面形成的产物膜越致密和完整,溶液中的Cl-吸附于表面后不易渗透至内部,从而使合金耐蚀性得到提高。

MgF_(2)涂层对Mg-Zn-Ca合金在模拟体液中应力腐蚀开裂行为的影响

采用慢应变拉伸测试方法对Mg-3wt.%Zn-0.2wt.%Ca(质量分数)(MZC)合金和氟化镁(MgF_(2))涂层Mg-3wt.%Zn-0.2wt.%Ca合金(MZC-MF)的应力腐蚀开裂行为进行研究。结果表明,MgF_(2)涂层可以显著提高MZC合金在模拟体液(SBF)中的耐腐蚀性并延长其断裂失效时间。MgF_(2)涂层明显降低MZC合金在SBF中的应力腐蚀敏感性,应力腐蚀开裂敏感性指数(Iscc)分别降低21%(UTS),22%(tf),23%(δ),7%(φ)和15%(A)。

超声振动对Al-Zn-Mg-Cu合金时效组织和性能的影响

基于自制的超声振动装置对Al-Zn-Mg-Cu合金进行超声振动时效,采用室温拉伸试验、显微硬度测试、电导率测试、金相显微镜和扫描电子显微分析(SEM)等手段,采用单因素实验设计研究超声振动时效时间和时效制度对Al-Zn-Mg-Cu合金组织与性能的影响。结果表明:施加超声振动促进析出相的生长,随着超声振动时效时间的延长,合金电导率逐渐升高,硬度和抗拉强度逐渐降低,伸长率略微增加。金相分析表明超声振动的激振应力切割粗大的第二相粒子,使得黑色颗粒变小,最后溶解或消失。施加超声振动对晶粒大小、形状和数量无明显影响。同时激振应力使得位错塞积开通,降低位错密度,降低残余应力。通过SEM显微镜对拉伸断口观察发现随着施加超声振动时间的延长,韧性断裂的特征更明显,韧窝数量显著增多,韧窝尺寸变大,深度变深。

Microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg–xZn–0.2Ca alloys

The microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg xZn 0.2Ca (x=0, 1.0, 2.0, 3.0) alloys were investigated in this study. Findings from scanning electron microscope, X-ray diffraction and transmission electron microscopy results indicate that the amount of ternary Ca2Mg6Zn3 phase, as the only secondary phase in 1.0Zn, 2.0Zn, and 3.0Zn alloys, gradually increases with the addition of Zn, while the Mg2Ca phase was observed in the Mg 0.2Ca alloy only. Zn has a strong effect on the orientation and intensity of textures, which also influence mechanical behaviors, as revealed by electron back-scatter diffraction. Among all the alloys, the Mg 2.0Zn 0.2Ca alloy obtains the maximum tensile strength (278 MPa) and yield strength (230 MPa). Moreover, Zn addition has an evident influence on the corrosion properties of Mg xZn 0.2Ca alloy, and Mg 1.0Zn 0.2Ca alloy exhibits the minimum corrosion rate. This paper provides a novel low-alloyed magnesium alloy as a potential biodegradable material.

Microstructure and mechanical and corrosion properties of hot-extruded Mg–Zn–Ca–(Mn)biodegradable alloys

Biodegradable Mg-based implants are widely used in clinical applications because they exhibit mechanical properties comparable to those of human bone and require no revision surgery for their removal.Among Mg-based alloys,Mg–Zn–Ca–(Mn)alloys have been extensively investigated for medical applications because the constituent elements of these alloys,Mg,Zn,Ca,and Mn,are present in human tissues as nutrient elements.In this study,we investigated the effect of the hot extrusion temperature on the microstructure,mechanical properties,and biodegradation rate of Mg–Zn–Ca–(Mn)alloys.The results showed that the addition of Mn and a decrease in the extrusion temperature resulted in grain refinement followed by an increase in the strength and a decrease in the elongation at fracture of the alloys.The alloys showed different mechanical properties along the directions parallel and perpendicular to the extrusion direction.The corrosion test of the alloys in the Hanks’solution revealed that the addition of Mn significantly reduced the corrosion rate of the alloys.The Mg–2 wt%Zn–0.7 wt%Ca–1 wt%Mn alloy hot-extruded at 300℃ with an ultimate tensile strength of 278MPa,an yield strength of 229MPa,an elongation at fracture of 10%,and a corrosion rate of 0.3 mm/year was found to be suitable for orthopedic implants.

Microstructure refinement,mechanical and biocorrosion properties of Mg–Zn–Ca–Mn alloy improved by a new severe plastic deformation process

In this study,the microstructural evolution,mechanical properties and biocorrosion performance of a Mg–Zn–Ca–Mn alloy were investigated under different conditions of heat treatment,extrusion,one pass and two passes of half equal channel angular pressing(HECAP)process.The results showed significant grain refinement of the homogenized alloy after two passes of HECAP process from 345μm to 2μm.Field emission scanning electron microscopy(FESEM)revealed the presence of finer Mg_(6)Zn_(3)Ca_(2)phase as well asα-Mn phase after HECAP process.The results also showed that mechanical characteristics such as yield strength,ultimate tensile strength and elongation of the HECAPed samples improved by~208%,~144%and~100%compared to the homogenized one,respectively.Crystallographic texture analysis indicated that most of the grains at the surface were reoriented parallel to the(0001)basal plane after HECAP process.Electrochemical corrosion tests and immersion results indicated that the sample with two passes of HEACP had the highest biocorrosion resistance confirming that the basal planes had the lowest corrosion rate compared to the non-basal ones.The mechanical behavior and bio-corrosion evaluation demonstrated that the HECAPed Mg–Zn–Ca–Mn alloy has great potential for biomedical applications and a mechanism was proposed to explain the interrelations between the thermomechanical processing and bio-corrosion behavior.

Effect of non-isothermal aging on microstructure and properties of Al−5.87Zn−2.07Mg−2.42Cu alloys

The evolution of microstructure and properties of Al−5.87Zn−2.07Mg−2.42Cu alloys during non-isothermal aging was studied.The mechanical properties of the alloy were tested by stretching at room temperature.The results show that in the non-isothermal aging process,when the alloy is cooled to 140℃,the ultimate tensile strength of the alloy reaches a maximum value of 582 MPa and the elongation is 11.9%.The microstructure was tested through a transmission electron microscope,and the experimental results show that the GP zones andη'phases are the main strengthening precipitates.At the cooling stage,when the temperature dropped to 180℃,the GP zones were precipitated again.Besides,the experimental results show that the main strengthening phase during non-isothermal aging isη'phases.

Effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–Zn–Ca alloys

The effects of Zn content on the microstxucture and the mechanical and corrosion properties of as-cast low-alloyed Mg-xZn~.2Ca alloys （x = 0.6wt%, 2.0wt%, 2.5wt%, hereafter denoted as 0.6Zn, 2.0Zn, and 2.5Zn alloys, respectively） axe investigated. The results show that the Zn content not only influences grain refinement but also induces different phase precipitation behaviors. The as-cast microstxucture of the 0.6Zn alloy is composed of ct-Mg, Mg2Ca, and Ca2Mg6Zn3 phases, whereas 2.0Zn and 2.5Zn alloys only contain ct-Mg and Ca2Mg6Zn3 phases, as revealed by X-ray diffraction （XRD） and txonsmission electron microscopy （TEM） analyses. Moreover, with in- creasing Zn content, both the ultimate tensile strength （UTS） and the elongation to fracture first increase and then decrease. Among the three investigated alloys, the largest UTS （178 MPa） and the highest elongation to fracture （6.5%） are obtained for the 2.0Zn alloy. In addition, the corrosion rate increases with increasing Zn content. This paper provides on updated investigation of the alloy composi- tion-microstxucture-property relationships of different Zn-containing Mg-Zn-Ca alloys.

Corrosion behaviour of Mg−Gd−Y−Zn−Ag alloy components with different sizes after cooling

The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.

Influence of Ca addition on microstructure,mechanical properties and corrosion behavior of Mg-2Zn alloy

The microstructure,mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-x Ca(x=0,0.2,0.4,0.8)alloys have been investigated in this study.Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration.Moreover,the alloys with different contents of Ca exhibit the different phases formation behaviors,i.e.α-Mg+Ca_2Mg_6Zn_3 phases for Mg-2Zn-0.2Ca and Mg-2Zn-0.4Ca alloys,andα-Mg+Ca_2Mg_6Zn_3+Mg_2Ca phases for Mg-2Zn-0.8Ca alloy,respectively.Among all the alloys,the maximum ultimate tensile strength and elongation(161 MPa and 9.1%)can be attained for the Mg-2Zn-0.2Ca alloy.Corrosion tests in Hanks’balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy.The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail.