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 ℃.

TEM microstructure of rapidly solidified Mg-6Zn-1Y-1Ce alloy

Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microstructure of RS ribbons.The results show that there is high density of particles distributed within grains and at grain boundaries in the region near wheel side.The particle density is decreased in the middle region and free surface region.The alloy is predominantly composed of supersaturated--Mg solid solution,T phase and W phase;meanwhile,a few icosahedral quasicrystalline and Mg4Zn7 particles are also observed.The T phase is confirmed having a body-centered orthorhombic structure that is transformed from the body-centered tetragonal structure Mg12Ce phase due to the partial substitution of Mg atoms by Zn.

Cu含量对Zn-1.2Mg合金组织与力学性能的影响

为改善Zn-Mg可降解生物合金的力学性能,本文采用金属型铸造的方法,制备了Zn-1.2Mg-x Cu(x=0,1.22.2)锌合金,研究了Cu含量对锌合金的微观组织和力学性能的影响。结果表明,锌合金的微观组织主要由η-Zn(Zn固溶体)和Mg_(2)Zn_(11)金属间化合物组成;当Cu浓度为2.2%时,合金中出现ε-CuZn_(5)金属间化合物。锌合金的显微硬度、抗拉强度随Cu含量的增加而增加,在2.2%Cu时达到最大值,分别为227 MPa和148 HV。断口分析表明,锌合金的断裂方式主要为解理断裂。

Effects of Mg content on microstructure and mechanical properties of low Zn-containing Al-xMg-3Zn-1Cu cast alloys

Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.

Improved Corrosion Behavior of Biodegradable Mg-4Zn-1Mn Alloy Modified by Sr/F co-doped CaP Micro-arc Oxidation Coatings

The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.

Effect of heating temperature on the microstructure evolution of a Zn-Al-Mg coating on press-hardened steel

This paper addresses the microstructure evolution in the Zn-1.2Al-1.2Mg coating of press-hardened steel during heat treatment at temperatures ranging from 600 ℃ to 900 ℃.The presence of aluminum in the coating leads to substantial variation in the chemical composition and microstructure within the heat-treated layer.As the heat treatment temperature increases, the original Fe_(2)Al_(5) barrier layer between the coating layer and steel substrate is progressively dissolved and replaced by the aggregates of a new(FeAl) phase.At higher heat treatment temperatures, the(FeAl) phase gradually migrates to the subsurface layer of the coating.Meanwhile, Zn/Fe interdiffusion induces Γ-Fe_(3)Zn_(10)-phase formation in the original coating layer and α-Fe(Zn) solid solution formation at the zinc-substrate interface.These microstructure features suppress the high-temperature oxidation and evaporation of Zn.

铸造SiC_p-GR_p/Zn-35Al-1.2Mg复合材料的磨损特性

采用粉末压型烧结结合搅拌铸造在铝锌合金基体中添加不同含量石墨GR__p、SiC_p、SiC_p/Al、GR_p/Al和SiC_p+GR_p/Al材料制备了SiC_p-GR_p/Zn-35Al-1.2Mg复合材料。结果表明,SiC_p和GR_p增强体颗粒在基体中混合均匀,单添加SiC_p使基体硬度提高8.5%,单添加GR_p使基体硬度降低15.4%,混合添加使基体硬度降低6.2%;在150N磨损时Zn-Al合金基体温升速率最快,达到45.7℃/s,而仅添加GR_p的复合材料最低,为26.1℃/s。在磨损结束后,温降速率最大的是单独添加GR_p颗粒,达到50.4℃/s,而单独添加SiC_p的最低,为33.6℃/s;30N载荷下磨损600s,GR_p减摩效果最优,使基体磨损量降低19%,60N载荷下磨损600s时SiC_p和GR_p混合颗粒减摩抗磨效果最优,使基体磨损量降低17%,而150N载荷下磨损时单独添加SiC_p抗磨效果最优,使基体耐磨性能提高了34%。

An adaptive biodegradable zinc alloy with bidirectional regulation of bone homeostasis for treating fractures and aged bone defects

Healing of fractures or bone defects is significantly hindered by overactivated osteoclasts and inhibited osteogenesis in patients with abnormal bone metabolism.Current clinical approaches using titanium alloys or stainless steel provide mechanical support but have no biological effects on bone regeneration.Therefore,designing and fabricating degradable metal materials with sufficient mechanical strength and bidirectional regulation of both osteoblasts and osteoclasts is a substantial challenge.Here,this study first reported an adaptive biodegradable Zn-0.8 Mg alloy with bidirectional regulation of bone homeostasis,which promotes osteogenic differentiation by activating the Pi3k/Akt pathway and inhibits osteoclast differentiation by inhibiting the GRB2/ERK pathway.The anti-osteolytic ability of the Zn-0.8 Mg alloy was verified in a mouse calvarial osteolysis model and its suitability for internal fracture fixation with high-strength screws was confirmed in the rabbit femoral condyle fracture model.Furthermore,in an aged postmenopausal rat femoral condyle defect model,3D printed Zn-0.8 Mg scaffolds promoted excellent bone regeneration through adaptive structures with good mechanical properties and bidirectionally regulated bone metabolism,enabling personalized bone defect repair.These findings demonstrate the substantial potential of the Zn-0.8 Mg alloy for treating fractures or bone defects in patients with aberrant bone metabolism.

Developing Zn–1.5Mg Alloy with Simultaneous Improved Strength,Ductility and Suitable Biodegradability by Rolling at Room Temperature

This study systematically investigated the influence of the microstructure evolution,mechanical properties and corrosion behaviors on Zn–1.5Mg(wt%)alloy processed by room-temperature rolling.The as-cast Zn–1.5Mg alloy consists ofη-Zn matrix andη-Zn+Mg_(2)Zn_(11)eutectic structure.As rolling reduction increases,the average grain size of the alloy reduces from 42.9 to 1.7μm,and the eutectic structure undergoes fragmentation and refinement,changing from a network distribution surrounding the matrix to a lamellar alternating distribution with the matrix.The ultimate tensile strength of the as-rolled alloy(80%reduction)is increased to 366±3.7 MPa,along with a good elongation of 18.4%±2.0%.Immersion tests in Hanks’solution indicate that the initial corrosion rate of the 80%-rolled alloy is 0.030 mm/year and finally stabilizes at 0.034 mm/year when the immersion duration is extended to 21 days.According to X-ray diffractometer and X-ray photoelectron spectroscopy analyses,Ca_(3)(PO_(4))_(2),CaCO_(3),Ca(OH)_(2),Zn_(3)(PO_(4))_(2),Zn(OH)_(2),ZnO and a small amount of MgO and MgCO_(3)are the main corrosion products on the surface.Due to the microstructure refinement,the developed alloy exhibits uniform corrosion,and the corrosion morphology is dominated by pitting pits.