Mg-3.0Nd-0.2Zn-0.4Zr镁合金表面电沉积Cu镀层及其耐腐蚀性能

研究Mg-3.0Nd-0.2Zn-0.4Zr（NZ30K）镁合金上电沉积Cu镀层的前处理过程及耐腐蚀行为。研究结果表明：活化膜和浸锌层均优先在Mg12Nd共晶相表面沉积。Cu镀层能够为镁基体提供长达60 h的防护作用,这主要归因于其致密的镀层结构及浸泡过程中形成较稳定的钝化膜。热震试验证明镀层具有良好的结合力。     

The effects of heat treatment and zirconium on the corrosion behaviour of Mg-3Nd-0.2Zn-0.4Zr (wt.%) alloy

The corrosion behaviours of Mg-3Nd-0.2Zn (wt.%) (NZ) and Mg-3Nd-0.2Zn-0.4Zr (wt.%) (NZK) alloys were investigated in as-cast (F), solution-treated (T4) and artificially-aged (T6) conditions in 5% NaCl solution using immersion test and electrochemical measurements. The immersion test indicates that both NZ and NZK alloys exhibit better corrosion resistances in T4 and T6 states than in the F condition due to the galvanic corrosion between the cathodic Mg₁₂Nd compound and the anodic α matrix in the F condition. The NZK alloy demonstrates lower corrosion rates than the NZ alloy in three conditions, which indicates that the addition of zirconium has a beneficial effect on the corrosion resistance. It was discovered by field emission scanning electron microscope (FE-SEM) that the corrosion products of NZK-T6 formed in salt solution are composed of sandwich shape compounds, while that of NZ-T6 is composed of fine needle-like compounds and small particles. The former are more uniform and compact than the latter and can play a more protective role for the alloy. Electrochemical measurements also confirmed that the more protective film formed on the NZK than on the NZ alloy.     

Research on Laser Welding of Mg-Rare Earth Alloy Mg-3Nd-0.2Zn-0.4Zr

The welding process of Mg-rare earth alloy Mg-3Nd-0.2Zn-0.4Zr (NZ30K) was studied using 15 kW high-power CO₂ laser, the microstructure and performance of the typical welded joints had been analyzed and tested. There is no softening zone according to the microhardness test of the welded joint. The microstructure of the fusion zone consists of α-Mg-phase and β-phase (Mg₁₂Nd).The results show that Mg-rare earth alloy NZ30K can be well joined with the high power laser and the welded joint has good performance.     

热处理对挤压态Mg-2.7Nd-0.2Zn-0.4Zr合金组织、力学性能和体外降解行为的影响(英文)

设计了Mg-2.7Nd-0.2Zn-0.4Zr(质量分数,%)镁合金作为可降解生物医用材料。对固溶处理后的铸锭进行了热挤压处理,然后对挤压棒分别进行了时效处理、固溶处理及固溶+时效处理。利用光学显微镜和扫描电镜观察了合金的组织,测试了合金的室温力学性能,采用析氢和失重法测试了合金在模拟体液中的降解行为,用扫描电镜观察了降解产物形貌及洗去降解产物后的形貌。结果表明:固溶处理后合金的晶粒明显长大,固溶处理显著提高挤压态合金的伸长率,但降低了合金的强度,而时效处理可提高合金的强度,降低合金的伸长率;热处理可降低合金的屈强比。体外降解实验结果表明:固溶处理使合金的降解速率稍微加快,而时效处理则能稍微减慢合金的降解速率。     

热处理过程中Mg-2Nd-4Zn-1Zr合金微观组织的结构特征(英文)

对比研究了Mg-2Nd-4Zn-1Zr合金在铸态和热处理态下显微组织结构的演变。借助TEM、SEM和XRD等研究发现,合金中的第二相有几种不同的种类特征。在铸态下,合金中存在的共晶化合物是由Mg、Nd和Zn构成的两种不同类型的三元相:T相和W相。然而,经过热处理,随着时间和温度的变化,T相几乎完全溶解进入α-Mg基体中,但W相仍然大量剩余在基体中。此外,随着热处理时间的延长,沿晶界分布的第二相的形貌由连续分布的网状逐渐转变为球状。在热处理过程中,合金中W相是一种高热力学稳定相,其数量随着热处理的进行而逐渐减少,并最终粗化、稳定地存在于基体中。     

固溶温度对Mg-2Nd-2Gd-0.3Sr-0.2Zn-0.4Zr镁合金腐蚀性能的影响

利用扫描电镜、能谱仪、X射线衍射仪分析了不同固溶处理温度下Mg-2Nd-2Gd-0.3Sr-0.2Zn-0.4Zr镁合金的显微结构,采用析氢和质量损失法测试了合金在模拟体液中的腐蚀性能。结果表明,随着固溶温度的升高,合金中共晶相含量减少,且由相对连续分布转变为不连续性分布,晶粒有所长大,晶粒内部针状析出相增多;合金在模拟体液中的腐蚀速率顺序为540℃495℃525℃510℃,并呈均匀腐蚀,表明当合金中共晶相连续分布时,耐蚀性能较好,当共晶相不连续分布时,共晶相含量越少合金的耐蚀性越好,且其含量和分布对合金腐蚀方式没有明显影响,而晶粒内富Zr析出相增加了合金局部腐蚀倾向性。     

生物可降解Mg-3Zn-0.8Zr-xMn合金的组织与性能

开发具有良好生物相容性、耐蚀性及综合力学性能的镁合金是当前可降解金属研究领域的重要方向,本文选取具有良好生物相容性的Zn、Zr、Mn合金元素,通过真空熔炼法制备了新型的Mg-3.0%Zn-0.8%Zr-x%Mn(质量分数,x=0,0.1,0.5,1.0,1.5)系列合金。研究了Mn含量变化对该类合金组织、力学性能及腐蚀降解行为的影响。结果表明:Mn的添加可以细化挤压态Mg-Zn-Zr合金的晶粒尺寸;合金的抗拉强度和屈服强度随着Mn含量的增加先升高后降低,在Mn含量为1.0%时,抗拉强度达到255 MPa,电化学及浸泡测试结果表明Mn的添加使合金的自腐蚀电位增加,耐蚀性能升高,当Mn含量为1.0%时,合金耐蚀性能最好;本研究成分范围内Mg-3Zn-0.8Zr-1Mn合金有最佳的综合力学及耐蚀性能。     

柠檬酸钠对AZ31镁合金阳极氧化膜耐蚀性的影响

研究了在电解液100g/LNa28407,50g/LNaA102中,加入不同浓度柠檬酸钠对阳极氧化膜层微观结构及耐腐蚀性能的影响.通过SEM和极化曲线分别研究了AZ31镁合金阳极氧化膜的表面形貌和耐蚀性.结果表明:当柠檬酸钠加入量为10g/L时,氧化膜层均匀、致密,孔径明显减小;从极化曲线可以看出,自腐蚀电位Ecorr为-0.614V,自腐蚀电流密度icorr为17.09μA·cm-2当电位在-0.478V～ 0.043V时,膜层发生钝化,当电位达到0.043V以后,发生了二次钝化,说明柠檬酸钠加入量为10g/L时,膜层在3.5%NaCI溶液中出现钝化膜破裂后自修复的现象.     

Effect of Dy addition on microstructure and mechanical properties of Mg-4Y-3Nd-0.4Zr alloy

Minor Dy element was added into a Mg-4Y-3Nd-0.4Zr alloy, and its effects on the microstructure and the mechanical properties at elevated temperatures were investigated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microstructures. The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg-RE phases were Mg₅RE and Mg₃RE₁₇, respectively, and distributed mainly along grain boundaries. After a solution treatment, the eutectic Mg₅RE phases were dissolved into the matrix, whereas the Mg₃RE₁₇ compound still remained. After peak aging, fine Mg-RE phases were precipitated homogeneously within the matrix of the alloys containing Dy. Dy addition can result in a significant improvement in the tensile strength at both room and elevated temperatures, and a slight decrease in the elongation.     

稀土元素Dy对Mg-2Zn-0.5Zr生物镁合金组织与性能的影响

通过拉伸试验、浸泡实验、电化学测试、扫描电镜(SEM)以及光学显微镜(OM)等方法研究了Dy含量对Mg-2Zn-0.5Zr-xDy生物镁合金微观组织、耐腐蚀性能和力学性能的影响。结果表明:随Dy含量的增加,合金的晶粒尺寸逐渐变小,第二相逐渐增多且主要沿晶界分布,合金的平均腐蚀速率先降低后升高,合金的力学性能先升高后降低;当Dy含量为1.5 mass%时,合金的耐蚀性能和综合力学性能均最好,平均腐蚀速率从未添加稀土元素时的1.28 mm/a降为0.92 mm/a,抗拉强度和伸长率分别为154 MPa和8.6%。     

Age hardening characteristics and mechanical properties of Mg-3.SDy-4.0Gd-3.1Nd-0.4Zr alloy

Age hardening characteristic and tensile property of Mg-3,5Dy-4.0Gd-3.1Nd-0.4Zr alloy were investigated. The alloy exhibits a considerable age hardening effect up to 250 ℃. Increasing the aging temperature leads to a shorter aging time to reach the peak hardness and a lower peak hardness. The tensile results show that the peak-aged specimens have higher tensile strength at the temperature below 200℃. However, with the increase of temperature further, the tensile strength decreases dramatically and elongation increases drastically. The loss in tensile strength and increase in elongation at high temperature are possibly associated with the instability of secondary precipitates. The fracture mechanism of alloy transfers from intergranular to transgranular with the increase of experimental temperature.     

热处理工艺对Mg-5Y-3Nd-1Gd-0.4Zr镁合金冲击韧性的影响

采用冲击实验研究了热处理工艺对Mg-5Y-3Nd-1Gd-0.4Zr镁合金U型缺口和无缺口试样的冲击韧性的影响,同时研究了时效时间对于时效态样品冲击性能缺口敏感性的影响.结果表明:固溶处理后合金的冲击韧性最高,断口形貌具有韧脆混合断裂特征,而时效后合金的冲击韧性迅速降低,断口形貌呈现脆性断裂的特征.这是由于固溶处理后合...     

Effects of Ce on microstructure of semi-continuously cast Mg-1.5Zn-0.2Zr magnesium alloy ingots

Mg-1.5Zn-0.2Zr-xCe (x=0, 0.1, 0.3, 0.5, mass fraction, %) alloys were prepared by conventional semi-continuous casting. The effect of rare earth Ce on the microstructure of Mg-1.5Zn-0.2Zr-xCe alloys was studied and the distribution of Ce was analyzed by optical microscopy (OM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicate that Ce element exists in the form of Mg12Ce phase and has an obvious refining effect on the microstructure of test alloys. As the Ce content increases, the grain size reduces, the grain boundaries turn thinner, and the distribution of Mg12Ce precipitates becomes more and more dispersed. The Mg-1.5Zn-0.2Zr alloy with 0.3%Ce has the best refinement effect. From center to periphery of the ingot, the amount of granular precipitates in the grain reduces. In longitudinal section of the ingot, some relative long columnar grains appear.     

Characterization of plasma electrolytic oxide formed on AZ91 Mg alloy in KMnO4 electrolyte

The aim of this work is to investigate microstructure, corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO₄ contained solution. There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage. The thickness of oxide layer increases with increasing coating voltage. The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn₂O₃. Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage. The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer. The inner barrier layer composed of the MgO and Mn₂O₃ may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test. Nanohardness values increase with increasing coating voltage. The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO₄.     

Influence of heat treatment on microstructure and mechanical properties of Mg-10Gd-3Y-1.2Zn-0.4Zr alloy

Microstructure evolution and mechanical properties of the cast Mg-10Gd-3Y-1.2Zn-0.4Zr(mass fraction,%) alloy during annealing at 798 K for different time were investigated.In the as-cast state,the microstructure consists ofα-Mg,Mg_5(Gd,Y,Zn) eutectic compounds and stacking faults(SF) of basal plane distributed from grain boundary to inner grain.During heat treatment at 798 K,the SF and parts of eutectic compounds dissolve into the matrix gradually,simultaneously,a new straight lamellar phase with 14H typ...     

Influence of potassium pyrophosphate in electrolyte on coated layer of AZ91 Mg alloy formed by plasma electrolytic oxidation

The effect of potassium pyrophosphate in the electrolyte on plasma electrolytic oxidation (PEO) process for AZ91 Mg alloy was investigated. The morphologies and chemical compositions of the coating layer on the AZ91 Mg alloy were evaluated and corrosion resistance was also estimated by potentiodynamic polarization analysis. The coating layer on AZ91 Mg alloy coated from the Bath 2 containing 0.03 mol/L of potassium pyrophosphate for 360 s exhibited considerably dense structure and contained 11%–18% (mass fraction) of phosphorous. The higher content of phosphorous of coating layer coated from Bath 2 could be detected at the bottom of oxide layer, which strongly implied that the phosphorous ion might be concentrated at the barrier layer. Corrosion potential of coating layer of AZ91 Mg alloy increased and corrosion current density decreased with increasing the concentration of potassium pyrophosphate. The polarization resistance (R_p) of coating layer of AZ91 Mg alloy coated from Bath 2 was 4.65×10⁷ Ω/cm², which was higher than that (R_p=3.56×10⁴ Ω/cm²) of the sample coated from electrolyte without potassium pyrophosphate. The coating layer coated from Bath 2 containing 0.03 mol/L potassium pyrophosphate exhibited the best corrosion resistance.     

Environmental friendly anodizing of AZ91D magnesium alloy in alkaline borate-benzoate electrolyte

A kind of environmental friendly anodizing routine for AZ91D magnesium alloy, based on an alkaline borate-sodium benzoate electrolyte (NaBz) was studied. The effect of NaBz on the properties of the anodized film was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results showed that the anodizing process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependent on the concentration of NaBz. In the presence of adequate NaBz, a thick, compact and smoothing anodized film with excellent corrosion resistance was produced. Moreover, the forming mechanism of the anodized film in the presence of NaBz additive was also approached, which was a suppression of arc discharge process by the adsorption of Bz⁻ on the surface of magnesium alloy substrate.     

铸造Mg-3Zn-1.5Cu-0.6Zr镁合金的时效硬化及析出相

利用光学显微镜、显微硬度计、X射线衍射仪、扫描电镜和透射电镜分析时效热处理(T6)后的Mg-3Zn-1.5Cu-0.6Zr镁合金的析出相。结果表明:合金铸态组织主要由初晶Mg基体和非平衡共晶组织(Mg+Mg2Cu,CuMgZn)组成;经固溶处理,晶界处大部分非平衡共晶组织溶解。经180℃,16h时效后,合金达到时效硬度峰值,此时晶内析出相主要有3类:1)少量棒状的过渡相β1′-α(可能是Mg4Zn7),其轴线垂直于(0001)Mg,长度大约50nm;2)大量弥散分布的板条状和棱柱状的β2′-MgZn2,其轴线垂直于(0001)Mg,长度为50～150nm,该相是合金的主要时效硬化相;3)少量短杆状的β-MgZn,其轴线平行于(0001)Mg,长度约20nm。