Sm对Mg-6Al合金腐蚀行为的影响

目前,有关镁合金中添加稀土Sm的改性研究多集中于力学性能方面,对增强耐腐蚀性能的影响研究较少。采用腐蚀试验,结合腐蚀速率计算、腐蚀形貌观察和显微组织分析,研究了添加不同含量的Sm对Mg-6Al合金在0.5%(质量分数)Na Cl溶液中腐蚀行为的影响。结果表明:随着Sm含量从0.5%(质量分数,下同)增加到1.5%,Mg-6Al合金的腐蚀速率先降低后升高。向Mg-6Al合金中加入1.0%的Sm后,可细化显微组织,降低腐蚀速率,改善腐蚀形貌,显著提高合金的耐腐蚀性能。     

稀土Gd对AZ31镁合金耐蚀性能的影响

利用失重法研究不同Gd含量的AZ31镁合金在3.5%(质量分数,下同)Na2SO4溶液中的腐蚀行为,并采用OM,SEM和XRD等检测手段分析稀土Gd对AZ31镁合金微观组织、腐蚀速率和腐蚀形貌等的影响。结果表明:稀土Gd的添加能明显改善AZ31镁合金的耐蚀性能,且当Gd的添加量小于4.12%时,合金的耐蚀性能会随着Gd含量的增加而提高,但继续增大Gd含量时合金的耐蚀性能反而会出现一定程度的下降,其原因是合金中添加过多的Gd后,加剧了基体相与析出相之间的微电偶腐蚀,致使合金的耐蚀性能有所下降。故当Gd的添加量为4.12%时,AZ31镁合金的耐蚀性能最佳。     

微量稀土Nd对AZ91微观组织及腐蚀性能的影响

采用X-射线衍射(XRD)、扫描电镜(sEM)、能谱分析(EDS)、集气法、动电位极化及浸泡实验等手段和方法研究了添加微量稀土元素钕(Nd)对AZ91镁合金微观组织及耐蚀性的影响,并从热力学角度分析了Nd对提高合金耐蚀性的影响机制.结果表明.少量稀土Nd细化了合金的微观组织,使β-Mg17Al12相变得断续、弥散,生成了Al3Nd相及Mg-Al-Mn-Nd-Fe金属问化合物;稀土Nd使合金在3.5%NaCl溶液中的自腐蚀电位升高,且与Al、O生成了不连续的致密的氧化膜,提高了合金的耐腐蚀性能;添加1.0wt%Nd时合金的耐蚀性最佳,腐蚀速率为0.28 mg·cm-2·d-1,比AZ91合金下降了一个数量级.     

Nd对AZ91镁合金显微组织和耐腐蚀性能的影响

用金相显微镜、扫描电镜和静态质量损失法对AZ91-xNd镁合金(x=1.1%,1.4%,1.9%)的微观组织和腐蚀性能进行表征,研究了Nd对AZ9l镁合金显微组织和耐腐蚀性能的影响.结果表明:稀土Nd的添加明显细化了合金的组织,使半连续网状β(Mgl7Al12)相变为细小的长条状,且分布更加均匀.在合金中还生成了颗粒状...     

稀土对AZ91镁合金干/湿循环腐蚀产物及阻抗行为的影响

采用扫描电镜(SEM)、X射线衍射(XRD)、能谱分析(EDS)研究添加(La,Ce)混合稀土前后AZ91镁合金在融雪剂溶液中经历干/湿交替循环腐蚀后腐蚀产物的组成和结构。结果表明:未添加(La,Ce)混合稀土的AZ91镁合金的腐蚀产物主要由Mg(OH)_2,MgO,CaCO_3及Mg_6Al_2CO_3(OH)_(16)·4H_2O组成;而添加混合稀土的AZ91镁合金表面生成了(La,Ce)AlO_3等含稀土元素的腐蚀产物,同时腐蚀产物出现致密层。不同周期干/湿交替循环腐蚀的电化学阻抗谱(EIS)测试结果表明,添加(La,Ce)混合稀土的镁合金在相同腐蚀周期的阻抗谱幅值均高于AZ91镁合金的阻抗谱幅值,稀土的添加有助于降低阻抗谱的弥散效应,表明(La,Ce)混合稀土可以提高AZ91镁合金在干/湿交替腐蚀环境中的耐蚀性和腐蚀产物膜的稳定性。     

海水中小球藻对Mg-3Y-1.5Nd镁合金腐蚀行为的影响

采用X射线衍射、扫描电子显微镜、X射线能谱仪等表面分析技术以及电化学技术,以稀土镁合金Mg-3Y-1.5Nd为基体,研究小球藻对其腐蚀行为的影响。结果表明:含小球藻培养液和不含小球藻培养液的镁合金表面主要腐蚀产物均为Mg(OH)2,Mg 3(PO4)2以及Mg 2(OH)3 Cl;含小球藻培养液的镁合金表面腐蚀产物中镁元素的占比较未含小球藻要小(29.6%vs 39.8%);腐蚀产物存在疏松的结构有利于腐蚀性离子侵入,促进镁合金的进一步腐蚀;小球藻的光合作用导致生物膜保护层下出现高浓度的溶解氧,使氧还原阴极电流变大,从而增大Mg-3Y-1.5Nd合金的腐蚀速率。综上所述,当小球藻存在时,Mg-3Y-1.5Nd合金受到的腐蚀更为严重。     

Ce和均匀化对Mg-2.0Zn-1.0Mn镁合金组织和性能的影响

在Mg-2.0Zn-1.0Mn镁合金中添加稀土Ce进行均匀化和挤压实验,分析稀土Ce和均匀化对ZM21镁合金组织和性能的影响规律。结果表明,添加稀土Ce可以有效细化ZM21合金的晶粒,提高ZM21镁合金的力学性能,降低ZM21镁合金凝固过程中的潜热和凝固温度范围。均匀化退火对ZM21镁合金挤压制品的性能和组织影响较小,但对ZM21+Ce镁合金的性能和组织影响明显,两种合金的断口均为混合型断裂,其中ZM21+Ce镁合金倾向于韧性断裂。     

时效态Mg-Gd-Y-Nd合金的组织结构及耐腐蚀性能

镁合金中加入Gd、Y、Nd等元素能提高其耐蚀性能,但目前对同时加入3种元素的情况研究较少。采用熔炼法制备了Mg-10Gd-3Y-Nd合金,并对其进行时效处理。利用金相显微镜、扫描电镜、X射线衍射仪等研究了时效态Mg-10Gd-3Y-Nd合金的微观组织及物相。通过静态失重法研究了时效态合金在不同浓度NaCl溶液中的耐腐蚀性能。结果表明:时效态合金主要由基体α-Mg和晶间共晶相(Mg_5Gd、Mg_(24)Y_5)组成,Gd能够良好地固溶于镁合金基体中;随着NaCl溶液浓度的增加,时效态合金的腐蚀速率增加,腐蚀深坑严重,颗粒状腐蚀物逐渐转为粉状;第二相颗粒的存在能阻止腐蚀过程向更深的晶粒区域发展,降低了腐蚀程度,提高了合金的耐腐蚀性。     

Nd、Y对AZ31镁合金热轧退火薄板耐蚀性的影响

为提高AZ31镁合金热轧退火薄板的耐蚀性,本实验在合金中分别添加单一Nd和复合Nd+Y稀土元素,采用盐雾腐蚀和电化学腐蚀实验方法对其耐蚀性展开研究,并利用扫描电镜(SEM)、X射线衍射(XRD)仪对合金和腐蚀产物的微观组织及结构进行观察分析。结果表明:添加稀土元素Nd、Y后,AZ31镁合金表面可形成更为耐蚀的含有稀土氧化物Nd_2O_3的腐蚀产物膜,提高对基体的保护作用;添加Nd、Y元素的AZ31镁合金中新的耐蚀相Al_2Nd和Al_2Y析出,有害相β-Mg_(17)Al_(12)减少,使合金自腐蚀电位正移,腐蚀电流密度减小,腐蚀速率减缓,耐蚀性明显提高;复合添加Nd+Y比单一添加Nd更有利于提高AZ31镁合金的耐蚀性,且添加量为0.5%Nd+0.5%Y时合金的耐蚀性能提高最为显著。     

新型Mg-8Li-5Al-5Ca合金的微观组织、力学及耐腐蚀性能

设计了新型高钙铝比Mg-8Li-5Al-5Ca合金,通过常温拉伸、失重法、pH测定和电化学测试等方法研究了合金的常温力学性能和耐腐蚀性能。采用扫描电镜(SEM)和X射线衍射(XRD)分析了基体和腐蚀产物相结构、合金显微组织以及腐蚀形貌。研究结果表明,这种镁锂合金形成Al2Ca相包围双基体(α-Mg+β-Li)的结构,挤压后基体组织和第二相粒子均明显细化。Mg-8Li-5Al-5Ca合金的耐腐蚀性能优于一般镁锂合金,且随着挤压比的增大进一步提升。该合金的力学性能协调了镁锂合金的优良塑性和高钙铝比镁合金的高强度,拥有较高的抗拉强度(222 MPa)和延伸率(8.3%)。     

固溶体Mg-5Al-xGd合金的制备及其压缩性能EI北大核心

利用Gd(0.00%,0.25%,0.50%,0.75%,1.00%,质量分数,下同)元素和凝固压力(3 GPa)调控Mg-5Al合金凝固组织结构,对合金样品进行压缩测试,并研究组织结构与室温压缩性能相关性。结果表明:常压石墨型铸造下,仅Mg-5Al-0.75Gd合金获得了晶界无共晶相生成、粒状Al2Gd相弥散分布在基体上、晶粒平均尺寸约为85μm的固溶体组织,其抗压强度和最大压缩应变分别为379 MPa和33.46%,高于存在晶间第二相的合金。3 GPa高压下,Gd含量≤0.25%合金的凝固组织为单一固溶体,Gd含量≥0.50%合金的晶界(枝晶间)有共晶Al_(2)Gd相生成。固溶体Mg-5Al-0.25Gd合金的平均晶粒尺寸是74μm,抗压强度是402 MPa,最大压缩应变是33.61%。Mg-5Al-0.75Gd合金的平均晶粒尺寸是38μm,抗压强度和最大压缩应变分别是341 MPa和25.12%,其性能低于Mg-5Al-0.25Gd合金。可见,晶间Al,Gd元素的存在形式是影响铸造Mg-Al合金力学性能的重要因素。     

Sb对Mg-5Al-2Sr合金组织和性能的影响

采用表面活性元素Sb微合金化的方法制备了Mg-5Al-2Sr-xSb(x=0,0.3,0.6,1.0)合金,通过金相显微镜、X射线衍射仪、扫描电镜和力学性能测试等方法研究了Sb含量对Mg-5Al-2Sr合金微观组织和力学性能的影响.结果表明,Mg-5Al-2Sr-xSb合金铸态组织主要由枝晶α-Mg、沿晶界或分布在枝晶间的层状或离异共晶的Al4Sr相、块状三元Mg9Al3Sr相(τ相)和颗粒状SbSr2相组成,随着Sb含量的增加,Sb-Sr2相的数量逐渐增多,τ相逐渐减少.Sb的质量分数为0.6%时,断续分布的Al4Sr相和细小弥散分布的Sb-Sr2相能够提高Mg-5Al-2Sr合金的室温和高温(150℃)机械性能.     

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.     

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.     

Mechanical properties and microstructure of SiC-reinforced Mg-(2,4)Al-1Si nanocomposites fabricated by ultrasonic cavitation based solidification processing

Nano-sized SiC enhanced magnesium matrix nanocomposites, Mg-2Al-1SiC with 2% SiC and Mg-4Al-1Si with 2% SiC, were successfully fabricated by ultrasonic cavitation based dispersion of SiC nanoparticles in Mg-(2,4)Al-1Si magnesium alloy melts. As compared to the magnesium alloy matrixes, the mechanical properties including tensile strength and yield strength of the Mg-2Al-1Si/2% SiC and Mg-4Al-1Si/2% SiC nanocomposites were improved significantly, while the ductility of magnesium alloy matrix castings was retained. While there were some SiC micro-clusters in the microstructure of nanocomposites, the SiC nanoparticles were dispersed well outside the areas of micro-clusters. Most micro-clusters were located along the grain boundaries while most separate SiC nanoparticles were embedded inside the grains. TEM study of the interface between SiC nanoparticles and Mg-(2,4)Al-1Si metal matrixes suggested that SiC bonds well with the metal matrixes without forming an intermediate phase.     

An additively manufactured Al-14.1Mg-0.47Si-0.31Sc-0.17Zr alloy with high specific strength,good thermal stability and excellent corrosion resistance

A novel Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was applied in the printing process of selective laser melting(SLM),and the corresponding microstructural feature,phase identification,tensile properties and corrosion behavior of the Al Mg Si Sc Zr alloy were studied in detail.As fabricated at 160 W and 200 mm/s,the Mg content of bulk sample decreased to 11.7 wt%due to the element vaporization at high energy density,and the density of this additively manufactured Al Mg Si Sc Zr alloy was 2.538 g/cm³,which is4.2%8.5%lighter than that of other SLM-processed Al alloys.After heat-treated(HT)at 325℃and 6 h,the microstructure was almost unchanged with an alternate distribution of fine equiaxed crystals and coarse columnar crystals.Nano-sized Al3(Sc,Zr)and Mg₂Si phases precipitated dispersedly in the Al matrix,and the tensile strength increased from 487.6 MPa to 578.4 MPa for precipitation strengthening and fine grain strengthening.With a fine grain size of 2.53μm,an excellent corrosion resistance was obtained for the as-printed(AP)Al Mg Si Sc Zr alloy.While the corrosion resistance of HT sample decreased slightly for the formation of non-dense oxide layer and pitting corrosion induced by diffuse precipitation distribution.This SLM-printed Al Mg Si Sc Zr alloy with high specific strength,good thermal stability and excellent corrosion resistance has broad prospects for the aerospace and automotive applications.     

Sb变质Mg-10Al合金的组织与力学性能

研究了不同Sb含量的Mg-10Al合金的微观组织及在室温和150℃高温下的力学性能。结果表明,加入适量的Sb,Mg-10Al合金中生成了弥散分布的针状Mg3Sb2相,α-Mg初晶显著细化,抑制了网状共晶组织的形成。当Sb含量为0.5%(质量分数)时,组织细化效果最佳。随着Sb含量的增加,室温及高温下合金的抗拉强度、屈服强度和伸长率先升高后降低,均在Sb含量为0.5%(质量分数)时获得最佳综合性能。Mg-10Al-0.5Sb合金在150℃的抗拉强度为180MPa、伸长率为19%,比Mg-10Al合金分别提高了30%和90%。此外,在150℃条件下,含Sb合金仍保持了与其在室温下相当的强度,而未添加Sb的Mg-10Al合金的强度则明显下降。     

铸态Mg-6Al-1.5Ca合金高温蠕变行为研究

采用光学显微镜（OM）、能谱分析（EDS）及X射线衍射（XRD）研究了铸态Mg-6Al-1.5Ca合金显微组织,并测试了合金的高温蠕变性能。结果表明：该合金由呈枝晶形貌的α-Mg基体和沿晶界分布的Al2Ca共晶相组成;通过幂律蠕变方程得出在150-200℃/50-90MPa下合金蠕变变形机制为扩散控制的高温位错攀移和晶界滑移机制;蠕变断裂行为可以用Monkman-Gran经验公式来描述,175℃蠕变断裂特征为脆性穿晶断裂。