Mg-Zn-Y-(Zr)合金中的二十面体准晶相（英文）

镁合金拥有许多独特优点,被认为是最具有应用前景的材料之一。然而,力学性能相对较低限制了镁合金的应用。二十面体准晶相作为一种相对优良的镁合金增强相,对Mg-Zn-Y-(Zr)合金性能有很大的影响。通过改变准晶相的体积分数,Mg-Zn-Y-(Zr)合金在室温下的的屈服强度可达到150-450 MPa,因而生成准晶相被视为一种改善镁合金性能的有效方法。本文讨论了一系列含有准晶的Mg-Zn-Y-(Zr)合金,包括准晶相的形成机理、准晶相的结构和其与镁基体的位向关系,以及准晶相对镁合金性能的影响。     

GH4720Li合金的枝晶间相与均匀化工艺

GH4720Li合金中Ti、Al含量较高,同时加入了Zr元素。铸态合金在枝晶间存在γ+γ′相共晶、MC型碳化物相、一次η相和Ni5Zr相。合金的凝固顺序为:L→γ;L→MC;L→γ+γ′;L→η;L→Ni5Zr。将铸态合金进行1130℃/20h+1180℃/10h两阶段均匀化处理可以消除枝晶间γ+γ′相共晶、一次η相和Ni5Zr相。     

医用Mg-Zn-Y-Ca-Zr镁合金组织及腐蚀性能研究

主要对医用镁合金材料的应用进行探究式试验,采用Zr元素作为主要合金化材料,它不仅能够细化合金晶粒,对基体点位也有明显的提高作用;另外,它还能够降低电偶的腐蚀。针对Mg-Zn-YCa-Zr合金结构中Zr含量的变化进行探究,通过多种试验进行分析。主要包括XRD、OM、SEM、电化学原理、失重试验以及析氢试验对合金内部的显微特征、组织特性以及腐蚀能力进行深层次探究。结果显示,在合金的应用中,适当添加Zr元素有助于增加镁合金基体电位。这种状态下,镁合金材料的电偶发生腐蚀的情况会大大降低。对于Mg-Zn-Y-Ca-Zr合金中Zr的含量进行了多项分析,探讨了Zr含量与性能之间的关系,最终可知,Mg-Zn-Y-Ca-Zr的合金研究对医学材料的开发有着积极的作用。     

添加铌和钽对TiMoZr合金变形机制和拉伸性能的影响

通过冷坩埚悬浮感应熔炼、轧制和固溶热处理制备Ti-8Mo-2Zr、Ti-8Mo-4Nb-2Zr和Ti-8Mo-4Nb-2Zr-2Ta(原子分数/%)钛合金,研究了铌和钽元素的添加对合金显微组织、拉伸性能和变形机制的影响。结果表明：3种合金的组成相均为单一β相,β相晶粒尺寸随着铌、铌+钽元素的添加逐步减小;Ti-8Mo-2Zr合金的变形机制以应力诱发α″马氏体相变和{332}孪生为主,而Ti-8Mo-4Nb-2Zr和Ti-8Mo-4Nb-2Zr-2Ta合金的变形机制以位错滑移为主;变形机制的转变导致合金强度的提高和塑性的降低,铌和钽元素添加产生的细晶强化和固溶强化效应进一步提高了合金的强度,Ti-8Mo-4Nb-2Zr-2Ta合金的抗拉强度高达970 MPa。     

低弹性模量Ti-Nb-Zr合金的显微组织与力学性能

为了降低医用植入物材料的弹性模量,通过选取不同含量的铌和锆,采用真空非自耗电弧炉熔炼了四种成分的Ti-Nb-Zr合金:Ti30Nb7Zr(T1)、Ti30Nb13Zr(T2)、Ti40Nb7Zr(T3)和Ti40Nb13Zr(T4);对四种合金进行了锻造处理,然后在β相区进行固溶,对其固溶后的力学性能、显微组织进行了研究.结果表明:T1和T2合金是β相+α',相的两相组织,随着锆含量不同,α'相形貌及数量也各不相同;T3和T4合金是单-β相组织;四种合金的弹性模量均低于80 GPa,其中T2合金的弹性模量为58 GPa,与人体骨骼的弹性模量最为接近.     

均匀化处理对铝锌镁钪合金组织和性能的影响

采用电导率测试、室温拉伸性能测试、扫描电镜和透射电镜分析等方法,研究了不同的均匀化处理对铝锌镁钪合金组织和性能的影响。结果表明:铸态铝锌镁钪合金为过饱和固溶体,合金元素在晶界偏析,形成了富锌、镁的非平衡共晶T相和富铁、硅、锰的杂质相;当均匀化温度为350℃,过饱和基体析出平衡相η-MgZn2;随着均匀化温度的升高,非平衡共晶T相逐渐溶入基体,电导率下降,晶内析出大量Al3(Sc,Zr)粒子,合金的热加工性能提高;470℃×12h是试验合金较适宜的均匀化制度。     

Zr基AB2型储氢合金组织结构及电化学性能的研究

采用XRD物相分析、扫描电镜分析、透射电镜分析及电化学性能测试等方法，分别对铸态及快淬态Laves相Zr基AB2型储氢合金进行了组织结构及电化学性能方面的研究，结果表明，铸态合金由C15-Laves相，C14-Laves相及非Laves相ZrgNi11(AB2-1中)、Zr(Ni，Mn)Sn0．35(AB2-2和AB2-3中)组成，AB2-1的电化学性能明显好于另外两种合金。合金经过快淬处理后，由于部分非晶化，对电极的放电容量和活化性能都有严重的不良影响。     

钇元素及固溶处理对AZ31镁合金组织和性能的影响

通过力学性能检测、SEM和XRD分析,研究了钇元素及固溶处理对AZ31镁合金组织和性能的影响,并分析了其断裂方式。结果表明:稀土钇元素能够细化铸态α-Mg基体组织,对镁合金具有较好的细晶强化作用;钇元素和铝元素形成的Al2Y化合物,在细化晶粒的同时均匀分布于晶界处,可强化晶界,提高合金的力学性能;钇元素质量分数为1.0%时,合金的力学性能最佳;进行440℃×10h的固溶处理能使加入0.5%(质量分数)钇元素的合金组织最为均匀;加入钇元素后,合金以韧性断裂和准解理断裂相结合的方式断裂。     

深冷处理对铸态ZK60镁合金显微组织和力学性能的影响

选用工业化生产的半连铸ZK60镁合金为研究对象,采用力学性能检测设备、光学显微镜、X射线衍射仪和透射电镜等研究了深冷处理(77 K)对其显微组织和力学性能的影响.结果表明:深冷处理可以细化ZK60合金的显微组织,引起一定程度的晶粒转动并促进微细第二相析出,产生了细晶强化及第二相析出强化,使ZK60合金的屈服强度由150...     

医用Mg-Zn-Ca镁合金的腐蚀与力学性能研究

旨在研发一种新型可医用的生物镁合金材料,并通过试验确定合金中不同元素含量对合金综合性能的影响。通过制备不同钙元素含量的试样,开展了各类分析试验,测量了合金试样不同金相构成下的腐蚀性能和力学性能。主要开展了失重、电解、力学拉伸以及XRD、SEM等试验,从而确定了不同钙含量下镁合金的综合性能。研究结果表明,合金中钙元素的适量添加能增强合金的抗腐蚀能力,细化晶粒,改善合金组织,但是当合金中钙元素含量>0.5wt%时,合金中将产生一定量的Mg₂Ca相,使得合金金相组织被割裂,进而降低合金力学性能。确定了Mg-Zn-Ca合金中钙元素含量对合金各项性能的影响,对于Mg-Zn-Ca合金作为医用材料的研究具有重要意义。     

Zr对Zn-Al合金阻尼性能影响的研究

研究了微量Zr对Zn-Al合金阻尼性能的影响，用电阻炉石墨坩埚熔炼了Zn-Al合金和Zn-Al-Zr合金，对合金的显微组织进行了金相观察，用X射线衍射法进行了相结构分析，测量了铸态和淬火态在不同温度及频率的内耗。结果表明：添加微量Zr可以细化合金的铸态组织，但并不改变合金的相结构，无论是铸态还是淬火态下的阻尼性能均得到提高。     

微量银对铝-铜-镁系合金组织和力学性能的影响

介绍了铝-铜-镁系合金不同相区的析出特征,总结了微量银对不同相区的铝-铜-镁系合金组织和性能的影响.在不同的铜镁质量比的铝-铜-镁系合金中添加微量的银可以影响其时效过程,改变铝-铜-镁系合金常规析出相的结构,形成具有热稳定性更好的新析出相,从而提高合金强度和工作温度.     

钇稀土在Mg-Zn-Zr镁合金中的强化作用

通过金相、机械性能试验、X射线衍射、扫描电镜、透射电镜及电子探针地Mg-Zn-Zr镁合金和添加0.94%(wt)钇稀土的Mg-Zn-Zr镁合金进行了对比研究,研究结果表明,钇稀土的添加,可细化合金的晶粒,改善合金的金相组织。合金添加包后,除了锌元素易在晶界富集外,钇元素也趋向于在晶界富集,并能与锌生成钇-锌相。在晶内,少量钇能固溶在合金基体,同时也能与镁生成镁-钇相。合金添加0.94%wt的钇,可使热挤压态下的抗拉强度有较大提高,其作用主要是,钇可在合金中起到变质作用,改善合金的金相组织。同时在挤压工艺条件下,在合金内能产生大量弥散细小的钇-锌相、镁-钇相质点,弥散强化合金,同时也可使合金产业亚晶组织强化合金。     

The structure of SiC-reinforced Mg casting alloys

The nature of the interface and interfacial reaction products formed between SiC particles and magnesium has been studied in two SiC_p-reinforced magnesium casting alloys, ZC63 and ZE63. In ZC63, a thin amorphous film was observed at the interface of the SiC particles. Energy-dispersive X-ray and electron energy-loss spectroscopy methods were used to characterize the films. They were found to contain Si, O and Mg, with the Si tetrahedrally coordinated to the O. The alloy ZE63 contains Zr and mischmetal (Ce, La, Nd, Pr), all of which are strong oxide formers. In the as-cast state, patches or continuous fine-grained oxide films were found at the interface of the SiC reinforcing phase in this alloy. Electron diffraction was used to identify these oxides as the tetragonal form of ZrO₂ and cubic CeO₂.     

铝含量对粉末冶金制备镁铝锆合金组织和力学性能的影响

运用粉末冶金工艺制备了Mg-xAl-1.5Zr(x=0,2,4,6,8,质量分数/%)合金,研究了铝含量对其组织和力学性能的影响。结果表明:镁铝锆合金主要由α-Mg基体、锆颗粒、β-Mg17Al12相组成,还存在一些微小的孔洞;铝含量的增加使合金组织趋于均匀化;Mg-6Al-1.5Zr合金具有最高的硬度和抗弯强度,分别为79.7HV和224MPa,但其塑性较差,断口呈准解理断裂的特征。     

TEM and HREM study of Al3Zr precipitates in an Al-Mg-Si-Zr alloy

The structure of Al₃Zr precipitates in Al‐1.0Mg‐0.6Si‐0.5Zr (in wt.%) alloy was investigated using conventional transmission electron microscopy (TEM) and high‐resolution TEM (HREM). After annealing of the alloy in the temperature range 450–540 °C, spherical precipitates of metastable L1₂‐Al₃Zr phase appeared nearly homogeneously within the matrix, and elongated particles were found at grain boundaries. L1₂‐structured Al₃Zr were about 20–30 nm in diameter and coherent with the matrix. Inside some of them, planar faults parallel to {100} planes were revealed by use of HREM. Most probably, these faults are an indication of the transition stage of transformation to the stable D0₂₃‐type Al₃Zr phase. The elongated precipitates (about 100 nm) were identified as D0₂₂‐type Al₃Zr. Energy‐dispersive X‐ray analysis showed that they contain, apart from Al, mainly Zr with small amounts of Si. The substitution of Al by Si increased the stability of the D0₂₂‐Al₃Zr as compared with D0₂₃‐Al₃Zr.     

Effect of rare earth elements on tribological behaviour of magnesium alloys

Abstract

Present investigation deals with the wear behaviour of conventional cast Mg–5%Sn and Mg–5%Sn–2%Mm (Mm is misch metal) (wt.%) alloys studied through pin-on-disc wear experiments at four different loading conditions under ambient temperature. This study reports the effects of external applied load on the dry sliding wear rate and co-efficient of friction of both the alloys. It has been investigated that the volumetric wear loss increases with increasing applied load. It has also been found that the wear rate of Mg–5%Sn–2%Mm alloy is less than that of Mg–5%Sn alloy. The wear mechanism has also been studied through extensive scanning electron microscopy imaging. It has been investigated that wear occurs by delamination of flakes and ploughing (i.e., asperities).     

Field ion microscopy and 3-D atom probe analysis of Al3Zr particles in 7050 Al alloy

Field ion microscope images have been used to measure the local evaporation field of a Al3Zr particle in 7050 Al alloy. Using the matrix Al evaporation field (19 V/nm) as a reference, the evaporation field of Al3Zr has been estimated to be 36 V/nm, similar to the theoretical value for the field evaporation of Al2+ or Zr3+ ions. A strong local magnification effect from the large difference in evaporation fields between the particle and matrix has been found to cause a severe distortion of the apparent particle morphology in a three-dimensional atom probe reconstruction when using parameters based on the Al matrix. Use of the measured evaporation field for Al3Zr has allowed accurate reconstruction of the morphology of the particle. A simple worst-case analysis predicts that trajectory overlaps increase with increasing cross-section of particle, and the calculated overlaps agree well with experimental estimates of approximately 1.4-2.0 nm for variations in the particle cross-section from 7 to 12 nm. The chemical composition of Al3Zr in a 7050 Al alloy has been measured to be 64.8-67.7 at% Al, 23.6-24.8 at% Zr, 6.9-9.1 at% Zn, 0.4-0.7 at% Cu, 0.5-1.2 at% Mg, with a (Al+Zn)/Zr ratio close to 3. Specimen analysis temperatures of either 25 or 80 K show little effect on the measured chemical compositions of the particle.     

Microstructure of a spray-formed Al/SiC composite

The microstructure of an Al–6Cu–2Mn–0·45 Mg–1(Ag, Ti, V, Zr, Cr) alloy, reinforced with 13 vol.% SiC particles, made by spray deposition has been investigated by transmission electron microscopy, high-resolution electron microscopy and electron diffraction X-ray spectroscopy. Particular attention was focused on the influence of the reinforcement on the precipitation sequence. Instead of the expected precipitation sequence due to the high Cu/Mg ratio, there is an additional σ precipitate which was previously observed in A1 alloys containing silicon. This precipitate becomes predominant at the T6 temper. The new precipitation sequence for this reinforced alloy is therefore The precipitation of σ phase is believed to be due to the presence of SiC particles, and seems to be correlated with the occurrence of large Mn-rich particles. Although expected, no S phase precipitation is found to occur in the matrix grains. At the matrix grain boundaries, small Al₂Cu (θ) and Al₂CuMg (S), as well as Mn-rich precipitates are found. At the SiC particle surfaces, preferentially orientated Ag-rich and Mg-rich intermetallic precipitates are found. They can coexist with amorphous patches containing oxygen enclosed in an irregularly shaped Al₂Cu (θ) phase remaining from large crystalline areas which did not go into solution.     

Effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–Sm alloys

This study investigated the effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–4Sm alloys. The addition of 1.0 wt% Ca led to a significant grain refinement of Mg–4.0Sm alloys owing to the formation of rod‐like Mg2Ca phases that acted as active nucleates for the Mg matrix. The as‐cast Mg–4.0Sm–1.0Ca alloy showed the smallest grain size at 45 μm. Furthermore, the Mg–4.0Sm–1.0Ca alloy exhibited greater hardness, higher tensile strength, and higher yield tensile strength and elongation than the other two alloys with different Ca contents. These results were attributed to the grain refinement and precipitation strengthening of the Mg2Ca and Mg41Sm5 phases. Microsc. Res. Tech. 79:707–711, 2016. © 2016 Wiley Periodicals, Inc.