Biodegradable Zn–3Cu and Zn–3Cu–0.2Ti alloys with ultrahigh ductility and antibacterial ability for orthopedic applications

Zinc(Zn) and its alloys have been proposed as biodegradable implant materials due to their unique combination of biodegradability, biocompatibility, and biofunctionality. However, the insufficient mechanical properties of pure Zn greatly limit its clinical application. Here, we report on the microstructure, mechanical properties, friction and wear behavior, corrosion and degradation properties, hemocompatibility, and cytocompatibility of Zn–3 Cu and Zn–3 Cu–0.2 Ti alloys under three different conditions of as-cast(AC),hot-rolling(HR), and hot-rolling plus cold-rolling(HR + CR). The HR + CR Zn–3 Cu–0.2 Ti exhibited the best set of comprehensive properties among all the alloy samples, with yield strength of 211.0 MPa, ultimate strength of 271.1 MPa, and elongation of 72.1 %. Immersion tests of the Zn–3 Cu and Zn–3 Cu–0.2 Ti alloys in Hanks’ solution for 3 months indicated that the AC samples showed the lowest degradation rate,followed by the HR samples, and then the HR + CR samples, while the HR + CR Zn–3 Cu exhibited the highest degradation rate of 23.9 m/a. Friction and wear testing of the Zn–3 Cu and Zn–3 Cu–0.2 Ti alloys in Hanks’ solution indicated that the AC samples showed the highest wear resistance, followed by the HR samples, and then the HR + CR samples, while the AC Zn–3 Cu–0.2 Ti showed the highest wear resistance.The diluted extracts of HR + CR Zn–3 Cu and Zn–3 Cu–0.2 Ti at a concentration of ≤25 % exhibited noncytotoxicity. Furthermore, both the HR + CR Zn–3 Cu and Zn–3 Cu–0.2 Ti exhibited effective antibacterial properties against S. aureus.     

Ultrafine-grained Zn-0.45Li alloy with enhanced mechanical property,degradation behavior and cytocompatibility prepared by hot extrusion and multi-pass drawing

Biodegradable Zn-0.45Li alloys with high strength and ductility were successfully fabricated by hot extrusion and multi-pass drawing to obtain ultrafine-grained microstructures with a secondary phase of fine LiZn₄ participates. The mechanical properties, degradation behavior and cytocompatibility of the alloys were subsequently investigated. Results showed that grain refinement could be achieved in the alloys after hot extrusion and multi-pass drawing. The yield strength, ultimate tensile strength, and elongation to failure of the ultrafine-grained Zn-0.45Li alloys reached 416 MPa, 567 MPa and 55.4 %, respectively. Enhancements in both strength and elongation could be attributed to interactions between LiZn₄ and matrix dislocations, the pinning effect of LiZn₄ on grain boundaries, and grain refinement. Immersion tests and MTT cytotoxicity assay indicated that the Zn-0.45Li alloys have a corrosion rate and cytocompatibility similar to the values reported for biomedical implants.     

Fe和Ce 含量对Galfan合金力学性能及耐蚀性的影响

将真空熔炼的Zn-Fe-Ce中间合金加入到Zn-Al熔池中,制备Zn-5Al-0.1Ce-xFe和Zn-5Al-yCe-0.1Fe合金,分析了Fe和Ce含量对合金显微组织及力学性能的影响,并使用电化学工作站测试了合金的电化学性能。结果表明,在Zn-5Al-0.1Ce合金中Fe含量大于0.02%后会形成颗粒状的FeAl3Znx相。随着Fe含量的增加,FeAl3Znx相和先共晶的η-Zn相增加,Zn-Al共晶组织由层片状向点状转变。添加0.1%以下的Fe可提高Galfan合金的抗拉强度。但随着Fe含量的增加,合金的抗拉强度略有降低,Zn-5Al-0.1Ce-0.02Fe合金的综合力学性能最好。添加0.04%以下的Fe会提升合金耐蚀性。此外,随着Ce含量的增加,Zn-5Al-yCe-0.1Fe合金的抗拉强度有所降低,耐蚀性变化不明显。因此,在生产中需要根据镀层性能要求,严格控制合金液中的Fe和Ce含量。     

Microstructure and mechanical property of high strength Mg–Sn–Zn–Al alloys

This paper aims to reveal the microstructure and mechanical properties of as-cast and hot-rolled Mg–Sn–Zn–Al based alloys. Three alloys, Mg–5Sn–2Zn (TZ52), Mg–5Sn–2Zn–2Al (TAZ522) and Mg–5Sn–5Al–1Zn–0.2Mn (TAZM5510) alloys were studied. The results revealed that the as-cast alloys showed fine dendritic structures. The TAZM5510 alloys exhibited moderate yield strength of 98?MPa with good elongation of ～15%, which was comparable to several commercially used Mg die-castings. Mechanical properties were significantly improved after multi-pass rolling. The TZ52 sheet showed a high yield strength of 277?MPa with excellent ductility exceeding 30%, and the TAZM5510 sheet exhibited the highest tensile strength of 386?MPa while keeping desirable elongation of 16.6%. These sheets are termed as strong and ductile Mg–Sn–Zn–Al wrought alloys.     

Microstructural evolution,mechanical properties and corrosion behavior of as-cast Mg-5Li-3Al-2Zn alloy with different Sn and Y addition

Influences of Sn and Y on the microstructure,mechanical properties,and corrosion behavior of as-cast Mg-5Li-3Al-2Zn (LAZ532) alloy were investigated.The addition of Sn and Y refines grains and results in the formation of Mg2Sn and Al2Y phases,thus improving the mechanical properties of alloy by second phase strengthening and grain refinement strengthening.As-cast LAZ532 alloy shows typical filiform corrosion morphology,and the addition of Sn and Y does not change the corrosion mode of alloy.Ascast LAZ532-0.8Sn-1.2Y alloy shows excellent mechanical properties with yield strength of 166.2 MPa,ultimate tensile strength of 228.6 MPa and elongation of 14.8 ％,and exhibits the best corrosion resistance with the smallest corrosion current density and the lowest anodic dissolution rate.     

Fabrication and characterization of novel biodegradable Zn-Mn-Cu alloys

Zn-Mn-Cu alloys with micro-alloying of Mn and Cu in Zn are developed as potential biodegradable metals. Although the as-cast alloys are very brittle, their ductilities are significantly improved through hot rolling. Among the as-cast and the as-hot-rolled alloys, as-hot-rolled Zn-0.35 Mn-0.41 Cu alloy has the best comprehensive property. It has yield strength of 198.4 ± 6.7 MPa, tensile strength of 292.4 ± 3.4 MPa,elongation of 29.6 ± 3.8% and corrosion rate of 0.050-0.062 mm a~(-1). A new ternary phase is characterized and determined to be MnCuZn18, which is embedded in MnZn13, resulting in a coarse cellular/dendritic MnZn13-MnCuZn18 compound structure in Zn-0.75 Mn-0.40 Cu alloy. Such a coarse compound structure is detrimental for wrought alloy properties, which guides future design of Zn-Mn-Cu based alloys.The preliminary research indicates that Zn-Mn-Cu alloy system is a promising candidate for potential cardiovascular stent applications.     

Effect of minor content of Gd on the mechanical and degradable properties of as-cast Mg-2Zn-xGd-0.5Zr alloys

RE-containing Mg alloys used as biodegradable medical implants exhibit good promising application due to their good mechanical properties and degradation resistance. In this work, effect of Gd on the microstructure, mechanical properties and biodegradation of as-cast Mg-2Zn-xGd-0.5Zr alloys was investigated. The results showed that there were mainly α-Mg, I-phase, W-phase and MgZn2 phase in Mg-Zn-Gd-Zr alloys. With increase of the Gd content, the strength of the alloys was enhanced due to the second phase strengthening and grain refinement. The degradation resistance of Mg-2Zn-0.5Zr alloy was increased by adding 0.5%–1% Gd due to the uniformly distributed second phases which acted as a barrier to prevent the pitting corrosion. However, increasing Gd content to 2% reduced the degradation resistance of the alloy due to the galvanic corrosion between the matrix and the second phases.The good degradation resistance and mechanical properties of as-cast Mg-2Zn-1Gd-0.5Zr alloy makes it outstanding for biomaterial application.     

Microstructures, mechanical properties and in vitro corrosion behaviour of biodegradable Mg–Zr–Ca alloys

The microstructures, mechanical properties, corrosion behaviour and biocompatibility of the Mg–Zr–Ca alloys have been investigated for potential use in orthopaedic applications. The microstructures of the alloys were examined using X-ray diffraction analysis, optical microscopy and scanning electron microscopy. The mechanical properties of Mg–Zr–Ca alloys were determined from compressive tests. The corrosion behaviour has been investigated using an immersion test and electrochemical measurement. The biocompatibility was evaluated by cell growth factor using osteoblast-like SaOS2 cell. The experimental results indicate that the hot-rolled Mg–Zr–Ca alloys exhibit much finer microstructures than the as-cast Mg–Zr–Ca alloys which show coarse microstructures. The compressive strength of the hot-rolled alloys is much higher than that of the as-cast alloys and the human bone, which would offer appropriate mechanical properties for orthopaedic applications. The corrosion resistance of the alloys can be enhanced significantly by hot-rolling process. Hot-rolled Mg–0.5Zr–1Ca alloy (wt %) exhibits the lowest corrosion rate among all alloys studied in this paper. The hot-rolled Mg–0.5Zr–1Ca and Mg–1Zr–1Ca alloys exhibit better biocompatibility than other studied alloys and possess advanced mechanical properties, corrosion resistance and biocompatibility, suggesting that they have a great potential to be good candidates for orthopaedic applications.     

Zn对铸态Mg-Y-Nd-Zr合金组织和力学性能的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射分析及力学性能测试等研究Zn元素对Mg-Y-Nd-Zr铸态合金显微组织及力学性能的影响。结果表明:随着Zn含量的增加,Mg-Y-Nd-Zr-xZn(x=0.0%,0.5%,1.0%,1.5%,质量分数)合金的晶粒逐渐细化,平均晶粒尺寸由(57±0.8)μm细化至(30±0.3)μm,晶界处共晶相的体积分数也逐渐增加。Mg-Y-Nd-Zr铸态合金中主要存在Mg12Nd相和Mg24Y5相,加入0.5%Zn后,合金中出现Mg12YZn相。随Zn含量的增加,Mg12YZn相的体积分数不断增大,合金的力学性能逐渐提高。当Zn含量为1.0%时,合金具有最优的力学性能,其抗拉强度、屈服强度和伸长率分别为(208±5.9),(159±3.9)MPa和(7.5±0.2)%,较未加Zn的合金分别提高了18,42MPa和1.2%。     

钛增强Cu40Zn黄铜合金的粉末冶金制备及其力学性能

采用粉末冶金法将合金元素Ti加到Cu40Zn基体中制备钛黄铜,研究了Ti的添加量对黄铜微观组织、界面结构、相组成以及力学性能的影响。结果表明：Ti在基体中固溶析出并与Cu40Zn反应生成了亚微米级的Cu₂Ti₄O颗粒和Ti纳米团簇,随着Ti含量的提高钛黄铜的屈服强度、抗拉强度和硬度呈提高的趋势。增大位错运动阻力产生的第二相强化、钉扎产生的细晶强化以及加工硬化,使Cu40Zn的力学性能提高。综合性能良好的Cu40Zn-1.9Ti,其屈服强度、抗拉强度、延伸率和硬度分别达到375 MPa、602 MPa、17.7%和163HV。     

A high strength,wear and corrosion-resistant,antibacterial and biocompatible Nb-5 at.％ Ag alloy for dental and orthopedic implants

Refractory metal niobium (Nb) incorporated with a small amount of silver (Ag),the resulting Nb-Ag two-phase alloys,were fabricated by mechanical alloying and spark plasma sintering.The microstructure,mechanical properties,wear resistance,corrosion behavior,in vitro and in vivo antibacterial properties and biocompatibility of the Nb-Ag alloys were systematically investigated.The results show that the mechanical properties,wear resistance,corrosion resistance and antibacterial ability were significantly enhanced after addition of 5 at.％ Ag.The fabricated Nb-5 at.％ Ag alloy demonstrates high yield strength of up to ～ 1486 MPa and fracture strain of ～ 35 ％.The precipitated Ag particles could reduce friction and wear.The enhanced corrosion resistance was attributed to the higher relative density of the sintered alloys and the formation of a stable and dense passive film of niobium and silver oxides.In vitro and in vivo evaluations show that the Nb-5 at.％ Ag alloy also has strong antibacterial activity and good biocompati-bility and osteointegration ability.These results demonstrate great potential of the nanostructured Nb-Ag alloys for dental and orthopedic implants.     

Effects of Nd on microstructures and properties of extruded Mg-2Zn-0.46Y-xNd alloys for stent application

The microstructures, mechanical and corrosion properties of three extruded Mg-2Zn-0.46Y-xNd alloys (x = 0.0, 0.5, 1.0 wt%) were studied by optical microscopy, scanning electronic microscopy (SEM), electrochemical measurements and tensile tests. Microstructural observations indicated that Nd led to the uniformity and the variation of morphology of major second phase; tensile tests showed that Nd can improve the ductility at moderate amount (0.5 wt%) and will be detrimental up to 1.0%; Mg-2Zn-0.46Y-0.5Nd alloy exhibited excellent mechanical properties (σ_b, 269.0 MPa, σ_0.2, 165.6 MPa and elongation, 24%); electrochemical tests revealed that Nd can enhance the corrosion resistance and Mg-2Zn-0.46Y-1.0Nd alloy had lowest corrosion current density, which was reasoned that the line-shape and rodlike NdZn₂ phase might serve as corrosion barriers and the dissolved Nd can raise the electrode potential of the matrix.     

Enhancing mechanical properties and corrosion resistance of nickel-aluminum bronze via hot rolling process

The mechanical properties and corrosion behavior of as-cast, as-annealed and hot-rolled nickelaluminum bronze(NAB) alloy(Cu-9 Al-10 Ni-4 Fe-1.2 Mn, all in wt.%) in 3.5 wt.% Na Cl solution were investigated. The results show that annealing introduces a large number of k phases to precipitate in the k phase. However, after further hot rolling, the original continuous k phases are spheroidized and dispersed, increasing the strength, hardness, and elongation of the alloy. In addition to the enhanced mechanical properties, the corrosion resistance of the NAB samples is also improved significantly by hot rolling, as revealed by the mass loss measurements, electrochemical impedance spectroscopy(EIS), and cross-sectional corrosion morphology. Selective phase corrosion occurs by the preferential corrosion of the k phase, which acts as an anode to the k phases, and the uncorroded k phases are retained in the corrosion product film. The interfaces between the k phases and the surrounding corrosion products become discontinuous caused by the spheroidization of k phases, reducing the corrosion of the substrate by the corrosive medium via the channels. As a result, the corrosion rate and the maximum local corrosion depth of the hot-rolled NAB sample are greatly reduced.     

Microstructural,mechanical and tribological properties of Al–7Si–(0–5)Zn alloys

A series of Al–7Si–(0–5)Zn alloys were produced by permanent mould casting and their microstructure, mechanical and tribological properties were investigated in as-cast state. The microstructure of Al–7Si alloy consisted of α-Al dendrites surrounded by eutectic Al–Si mixture and a small amount of primary silicon particles. Addition of zinc into Al–7Si alloy resulted in the formation of α-solid solution and an increase in size and volume fraction of primary silicon particles. Moreover, these particles gathered inside interdendritic regions of the ternary Al–7Si–Zn alloys. The density, strength and hardness of Al–7Si–Zn alloys increased continuously with increasing zinc content, but their elongation to fracture and impact energy showed a reverse trend. It was also observed that zinc had no significant effect on the friction coefficient of the alloys, but their wear volume decreased with increasing zinc content up to 4%, above which the trend reversed. The wear surfaces of the alloys were characterized mainly by smearing layer with some degree of oxidation. In addition, delamination and fine scratches were observed on the worn surface. It was concluded that the addition of zinc up to 4% improves both mechanical and wear behaviour of Al–7Si alloy.     

稀土Er对A356铝合金微观组织和力学性能的影响

针对传统的A356铝合金,添加稀土元素是改善其微观组织并提高力学性能的有效途径。本工作通过示差扫描量热分析(DSC)、X射线衍射(XRD)、扫描电镜(SEM)等分析手段来研究稀土Er对铸态A356铝合金组织和性能的影响。结果表明,稀土元素Er是一种能够显著改善A356合金铸态组织的优良变质剂。Er的加入细化了初生α-Al相,二次枝晶间距降低,枝晶臂直径减小,同时对铸态组织中的共晶Si起到了变质作用。当Er含量达到0.4%(质量分数,下同)时,细化效果最为显著,二次枝晶间距由53.6μm减小到17.5μm,共晶硅形貌也由粗大的板条状转变为短棒或圆粒状。与A356合金相比,添加0.4%Er的合金样品的抗拉强度和伸长率分别提高了15.1%,29.8%。     

热处理对双相Mg-8Li-4Al-3Zn-La合金组织与性能的影响

分别对原始态的双相Mg-8Li-4Al-3Zn-La合金进行固溶及退火处理,通过光学显微镜、扫描电镜以及X射线衍射等方法研究合金在不同热处理状态下微观组织的变化,测定了合金硬度及拉伸性能并分析了断口。研究结果表明,经固溶处理后合金抗拉强度明显提高,由原来的194MPa提升到243MPa,延伸率由18%降至9%;而退火处理后其强度没有提升,塑性反而下降。此外,合金中两相组织与第二相分布具有明显差异,使得各相性能及其对热处理的反应不同。     

Microstructure,mechanical and corrosion properties and biocompatibility of Mg–Zn–Mn alloys for biomedical application

Mn and Zn were selected to develop a Mg–Zn–Mn magnesium alloy for biomedical application due to the good biocompatibility of Zn and Mn elements. Microstructure, mechanical properties, corrosion properties and biocompatibility of the Mg–Zn–Mn alloys have been investigated by use of optical microscope, scanning electron microscope, tensile testing, and blood hemolysis and cell toxicity. Microstructure observation has shown that the addition of Zn and the extrusion significantly refined the grain size of both the as-cast and the extruded magnesium alloys, which mainly contributes to the high tensile strength and good elongation. Polarization test has shown Zn could accelerate the formation of a passivation film, which provides good protection to the magnesium alloy against simulate body fluid. Cell culture and hemolysis tests have shown that the magnesium alloy did not have cell toxicity, showing good cytocompatibility, but the alloy caused hemolysis to blood system. It was suggested that surface modification have to be adopted to improve the blood compatibility of the magnesium alloy for the application in blood environment.     

Al-7Sn-1.1Ni-Cu-0.2Ti轴承合金微观组织与力学性能

采用扫描电镜、能谱分析、金相显微镜与WDW-100KN万能拉伸试验机研究Al-7Sn-1.1Ni-Cu-0.2Ti轴承合金的微观组织与力学性能,结合盘-销式摩擦磨损试验机考察合金不同组织状态的润滑性能。结果表明:Al-7Sn-1.1Ni-Cu-0.2Ti合金凝固收缩率为1.13%,铸态抗拉强度、屈服强度、伸长率与布氏硬度分别为191,147MPa,15.6%与34.6HBS,随着低温时效与退火热处理过程的进行,抗拉强度略有上升,屈服强度保持不变,伸长率与布氏硬度均呈现出先上升后下降的变化趋势;沿晶界分布的共晶Sn相形貌受界面张力作用逐步由板片状与骨骼状转变为层片状与短棒状,部分吸热脱溶析出在晶界处形成空腔结构,初生α-Al基体平均晶粒尺寸为182μm。与铸态和340℃退火6h相比,经175℃时效10h后,摩擦因数降低了28.6%与78.6%,体积磨损量减少了157.1%与471.4%,断口形貌以沿晶断裂与韧窝断裂为主。     

Microstructure and mechanical properties of Mg–8Li–xAl–0.5Ca alloys

The effect of the Al content on the microstructure and mechanical behaviour of Mg–8Li–xAl–0.5Ca alloys is investigated. The experimental results show that an as-cast Mg–8Li–0.5Ca alloy is mainly composed of α-Mg, β-Li and granular Mg₂Ca phases. With the addition of Al, the amount of α-Mg phase first increases and then decreases. In addition, the intermetallic compounds also obviously change. The microstructure of the test alloys is refined due to dynamic recrystallisation that occurs during extrusion. The mechanical properties of extruded alloys are much more desirable than the properties of as-cast alloys. The as-extruded Mg–8Li–6Al–0.5Ca alloy exhibits good comprehensive mechanical properties with an ultimate tensile strength of 251.2?MPa, a yield strength of 220.6?MPa and an elongation of 23.5%.     

Comparative studies on the microstructure evolution and fracture behavior between hot-rolled and as-cast Mg96ZnY3 alloys

Microstructure evolution and fracture mechanism of as-cast and hot-rolled Mg₉₆ZnY₃ alloys have been investigated in the present paper. Microstructure of the as-cast Mg₉₆ZnY₃ alloy consists of α-Mg dendrite and lamellar Mg₁₂YZn phase distributed mainly in interdendritic region. After a initial thickness reduction of ～ 62% through a series of rolling passes at 420 °C, the hot-rolled Mg₉₆ZnY₃ alloys were prepared by a final rolling reduction of 15% at 350 °C and 400 °C, respectively. The long period stacking order phase having a special orientation with α-Mg matrix in hot-rolled alloy was identified as 18R structure phase. Though highly dense dislocations were formed in the α-Mg matrix of the hot-rolled alloys, the parallel dislocations and sub-grain boundary were easily formed in the alloy during the recovery due to the relatively high working temperature of 400 °C. In the alloy rolled at 350 °C, the long period stacking order phase was traversed in the grain by the twins, which were induced by the relatively low working temperature. The morphology of dislocation and the influence of twin boundary may be the main reason for higher strength of the alloy rolled at 350 °C. While the tensile elongations for both as-cast and hot-rolled Mg₉₆ZnY₃ alloys are similar, their respective fracture mechanisms are different. The fracture along the phase interface of lamellar Mg₁₂YZn phase at grain boundary and cleavage fracture are considered as main fracture mechanisms for the as-cast alloy. The fracture caused by stress concentration at the phase interface between the matrix and Mg₁₂YZn phase in grain is the main fracture mechanism for the hot-rolled alloy.