Er元素对定向凝固Al-Zn-Mg-Cu-Zr合金微观组织和共晶相形貌的影响

采用定向凝固方法制备了Al-Zn-Mg-Cu-Zr-xEr（x=0,0.1,0.2,0.5,质量分数,%）4种合金棒。利用光学显微镜（OM）、电子探针（EPMA）、能谱分析（EDS）和其他方法研究了铸态合金的微观组织和第二相形貌。结果表明：Er元素能增加Al-Zn-Mg-Cu-Zr合金定向凝固组织的枝晶数量,并能减小合金的一次枝晶臂间距和二次枝晶臂间距。适量Er元素能减少合金第二相的含量并有利于形成圆形第二相。生成的Al₈Cu₄Er相会降低T相（AlZnMgCu）中的Cu含量,起到圆润T相边界的作用,改变了T相的形貌和内部结构,并且Al₈Cu₄Er相能充当T相的形核位置,使得一部分T相围绕该相生长。Er的添加会提高合金的显微硬度。     

Ho添加对Al-Zn-Mg-Cu合金均匀化热处理过程中微观组织和性能演变的影响

通过SEM、OM和DSC,研究添加Ho的Al-Zn-Mg-Cu合金均匀化热处理制度,测试不同均匀化热处理过程中合金的电导率和硬度变化。结果表明,铸态合金中存在4种第二相：T(AlZnMgCu),Al₇Cu₂Fe,Al₈Cu₄Ho 及S (Al₂CuMg),第二相导致合金元素分布存在严重微观偏析。合金在475 ℃均匀化热处理20 h后,T相完全回溶基体且未观察到S相,仅剩余Al₇Cu₂Fe和Al₈Cu₄Ho。硬度和电导率随T相的回溶而变化,T相的回溶使得合金硬度升高,电导率降低。同时,在475 ℃均匀化热处理5~20 h过程中,Al₃Ho相析出,这一现象引起硬度和电导率的升高。结合均匀化动力学分析,确定合金适宜的均匀化热处理制度为470~475 ℃/20~25 h。     

Er含量对ZL201A铝合金组织和力学性能的影响

通过金相显微镜、扫描电子显微镜、透射电子显微镜、能谱仪分析和力学测试,研究了添加Er对ZL201A铝合金的微观结构和力学性能的影响。结果表明,Er的加入使α-Al基体从柱状晶粒转化为细小的等轴晶粒,同时θ相（Al₂Cu）从细小的网络结构转变为弥散细小颗粒结构。当Er含量达到0.4%（质量分数）时,晶粒细化效应达到最大,合金的力学性能最佳;α-Al的平均晶粒尺寸为19 μm;抗拉伸强度和伸长率分别为298.14 MPa和6.56%;断裂模式从脆性断裂转变为韧性-脆性断裂,有利于铝合金的实际应用。当Er含量超过0.4%（质量分数）时,合金的晶粒尺寸增大,力学性能下降。     

基于磁过滤技术的热障涂层表面Al2O3 覆盖层抗CMAS腐蚀性能

为了提高热障涂层（TBC）的抗沉积物（主要成分为CaO、MgO、Al₂O₃和SiO₂,简称CMAS）腐蚀性能,采用磁过滤阴极真空电弧（FCVA）技术在TBC表面上制备了致密的Al₂O₃覆盖层,比较和分析了Al₂O₃改性TBC和沉积态TBC的润湿行为和抗CMAS腐蚀性能。结果表明：使用FCVA技术制备Al₂O₃覆盖层的过程对7%（质量分数）氧化钇稳定的氧化锆（7YSZ）相的结构无明显影响,且经Al₂O₃改性的TBC综合性能均优于沉积态TBC。在1250 ℃、CMAS腐蚀条件下,Al₂O₃覆盖层有效地限制了熔融CMAS在TBC表面上的扩散行为。同时,Al₂O₃填充了7YSZ柱状晶之间的间隔并且阻碍了熔融CMAS的渗透,证明了FCVA可作为一种制备Al₂O₃涂层的新方法以提高TBC的抗CMAS腐蚀性能,且Al₂O₃涂层及其制备过程对TBC的热震性能均无消极影响。     

Al9Fe0.7Ni1.3相对喷射沉积Al-Zn-Mg-Cu-Ni合金组织和性能的影响

本文利用喷射沉积技术合成含Ni的Al-Zn-Mg-Cu合金,合金中的Ni元素以亚微米球状Al₉Fe_0.7Ni_1.3化合物的形式存在。利用扫描电镜和电子背散射衍射、透射电镜以及拉伸测试研究了Al₉Fe_0.7Ni_1.3颗粒对合金固溶处理后组织和性能的影响。结果发现：Al₉Fe_0.7Ni_1.3颗粒主要在晶界附近分布,说明该颗粒在固溶过程中具有有力的抑制再结晶作用。固溶处理后,合金的拉伸强度为603 MPa,断裂延伸率为11.79%,主要断裂方式为穿晶延性断裂。实验结果表明亚微米球状Al₉Fe_0.7Ni_1.3化合物对合金性能有重要影响,可以产生细晶强化和Orowan强化,是合金发生穿晶延性断裂的主要原因。     

性能优异的SrO改性Pd-Rh双金属催化剂的制备

在浸渍到Al₂O₃载体材料上之前,通过将Sr的前驱体引入到贵金属Pd和Rh的混合盐溶液中,即采用共浸渍法制备了一系列SrO改性的Pd-Rh/Al₂O₃催化剂。结果表明,由于SrO的扩散障碍效应,适量SrO（1%~2%,质量分数）的引入有利于促进Pd,Rh的分散,并且能提高催化剂的水热稳定性。水热老化之后,催化剂能保持更高的Pd,Rh分散度,并且Pd,Rh能稳定在活性更好的氧化态。因此,适量SrO改性的Pd-Rh/Al₂O₃催化剂具有更好的还原性能和三效催化活性。然而,当向催化剂中引入过量的SrO,由于SrO占据了过量的Al₂O₃的表面,而且老化后会出现新的物相SrAl₂O₄,反而会对催化剂的性能产生不利的影响。总的来说,2% SrO改性的催化剂具有最优异的三效催化活性,水热老化之后,相比于空白的Pd-Rh/Al₂O₃催化剂,2%SrO改性的催化剂使CO,HC和NO的起燃温度分别降低了23,15和27 ℃。     

Ti-Cu-Ni-Nb-Al-Zr-Hf非晶钎料合金真空钎焊Ti50Al50 接头的界面组织与剪切强度

在钎焊温度1140~1220 ℃、钎焊时间30 min的工艺参数下,采用Ti-9.5Cu-8Ni-8Nb-7Al-2.5Zr-1.8Hf（质量分数,%）非晶钎料成功实现了Ti₅₀Al₅₀ (at%)合金的真空钎焊连接,并研究了钎焊温度对钎焊接头的显微组织、剪切强度的影响规律。结果表明,在任何钎焊温度下获得的Ti₅₀Al₅₀钎焊接头均有3个界面反应层且每个反应层都含有α₂-Ti₃Al和Ti₂Cu(Ni) 2个物相。随着钎焊温度的增加,α₂-Ti₃Al和Ti₂Cu(Ni)在钎焊接头中的尺寸与分布发生了明显的变化,尤其是等温凝固层Ⅱ中的Ti₂Cu(Ni)相。1200 ℃下稳定存在的连续α₂-Ti₃Al层Ⅰ对母材和钎料原子的相互扩散具有阻隔壁垒作用,温度一旦超过1200 ℃,α₂-Ti₃Al相变得不稳定使得连续α₂-Ti₃Al层被打破从而失去阻隔壁垒效应。在钎缝中析出且弥散分布的α₂-Ti₃Al对焊缝中物相的形成可以起到抑制形核和细化晶粒的作用。随着钎焊温度升高,Ti₅₀Al₅₀钎焊接头平均抗剪切强度先增加后减小,在钎焊温度1180 ℃、钎焊时间30 min时钎焊接头的抗剪切强度最大,达184 MPa。剪切断口表面呈典型解理断裂特征且α₂-Ti₃Al占绝大多数。     

γ-TiAl合金表面Al2O3/Al复合涂层的抗高温熔盐腐蚀性能研究

采用磁控溅射技术于γ-TiAl合金表面制备Al₂O₃/Al复合涂层。在850 °C下、 100 wt.% Na₂SO₄熔盐中观测Al₂O₃/Al复合涂层的高温腐蚀行为。结果表明,Al₂O₃/Al复合涂层具备由Al₂O₃表层、富Al中间层以及互扩散层组成的梯度结构,因而有效地提高了基体γ-TiAl合金的抗高温腐蚀性能。在腐蚀实验后,涂层试样表面相结构为Al₂O₃,TiO₂和TiAl₃。致密的Al₂O₃/Al复合涂层有效地抑制了O_2-,S_-和Na₊对基体γ-TiAl合金的侵蚀。并且,Al₂O₃/Al复合涂层的梯度结构亦使其表现出了优异的抗开裂和抗剥落性能。     

Cu-Fe64Ni32Co4合金显微组织及热物理性能研究

本研究利用相图计算的CALPHAD方法和真空电弧熔炼技术,设计并制备了Cu_x(Fe_0.64Ni_0.32Co_0.04)_100-x(x=30, 45, 60, wt. %)系列合金。实验研究了该系列合金在不同热处理工艺时的显微组织,热导率以及热膨胀系数。研究结果表明：Cu-Fe₆₄Ni₃₂Co₄系列合金在600 °C和800 °C时效处理后均为fcc富铜相和fcc富因瓦(铁镍钴)相组成的各向同性的多晶合金。该系列合金在1000 °C淬火并在600 °C时效处理50 h后,其热膨胀系数变化范围为6.88~12.36×10_-6 K_-1;热导率变化范围为22.91~56.13 W.m_-1.K_-1;其热导率明显高于因瓦合金,其中Cu₃₀(Fe_0.64Ni_0.32Co_0.04)₇₀与 Cu₄₅(Fe_0.64Ni_0.32Co_0.04)₅₅合金的热膨胀系数可以与电子封装中半导体材料的热膨胀系数相匹配。     

Er-Ba复合变质对Mg-2.5Si-4Zn铸造合金组织及性能的影响

镁合金中的强化相Mg₂Si可以显著提高合金的硬度、耐磨性，特别是耐高温蠕变性。但铸态过共晶Mg-Si合金中初生Mg₂Si棱角粗糙，共晶Mg₂Si具有复杂的汉字形态，会严重割裂合金基体。为了改善Mg-2.5Si-4Zn合金的性能，进行了添加Er/Er-Ba的变质实验，并通过光学显微镜（OM）、扫描电子显微镜（SEM）、能量色散光谱仪（EDS）和X射线衍射仪（XRD）研究了Er/Er-Ba对合金组织和Mg₂Si相的影响。利用计算机辅助电子加载拉伸试验机对力学性能进行了测试和分析。结果表明，在Mg-2.5Si-4Zn合金中加入0.6%（质量分数）的Er，其组织中的初生Mg₂Si从粗大的树枝状转变为规则的四方块状，而共晶Mg₂Si则从粗大的汉字状转变为更复杂的短棒状。随后加入0.8%的Ba后，初生Mg₂Si从规则的四边形块状进一步转变为带有沟槽和孔洞的不规则细小块状，共晶Mg₂Si在尺寸上细化效果显著，呈点线状弥散分布在合金基体中。当加入0.6%Er和0.8%Ba时，变质效果最佳。经Er-Ba复合变质的Mg-2.5Si-4Zn合金的力学性能得到显著改善，抗拉强度σ_b和伸长率δ分别提高到168 MPa和5.04%。     

Microstructural evolution of new type Al–Zn–Mg–Cu alloy with Er and Zr additions during homogenization

A comprehensive study on the microstructural evolution of a new type Al–Zn–Mg–Cu–Er–Zr alloy during homogenization was conducted by optical microscope, scanning electron microscope, transmission electron microscopy and X-ray diffraction analysis. The results show that serious segregation exists in as-cast alloy, and the primary phases are T(AlZnMgCu), S(Al₂CuMg) and Al₈Cu₄Er, which preferentially locate in the grain boundary regions. The soluble T(AlZnMgCu) and S(Al₂CuMg) phases dissolve into the matrix gradually during single-stage homogenized at 465 °C with prolonging holding time, but the residual Al₈Cu₄Er phase cannot dissolve completely. Compared with the single-stage homogenization, both a finer particle size and a higher volume fraction of L1₂-structured Al₃(Er, Zr) dispersoids can be obtained in the two-stage homogenization process. A suitable homogenization scheme for the present alloy is (400 °C, 10 h)+(465 °C, 24 h), which is consistent with the results of homogenization kinetic analysis.     

Preparation, microstructure and properties of molybdenum alloys reinforced by in-situ Al2O3 particles

The conventional molybdenum alloys, lacking of hard particles enhancing wear property, have relative poor wear resistance though they are widely used in wear parts. To resolve the above question, Mo alloys reinforced by in-situ Al₂O₃ particles are developed using powder metallurgy method. The in-situ α-Al₂O₃ particles in molybdenum matrix are obtained by the decomposition of aluminum nitrate after liquid-solid incorporation of MoO₂ and Al(NO₃)₃ aqueous solution. The α-Al₂O₃ particles well bonded with molybdenum distribute evenly in matrix of Mo alloys, which refine grains of alloys and increase hardness of alloys. The absolute density of alloy increases firstly and then decreases with the increase of Al₂O₃ content, while the relative density rises continuously. The friction coefficient of alloy, fluctuating around 0.5, is slightly influenced by Al₂O₃. However, the wear resistance of alloy obviously affected by the Al₂O₃ particles rises remarkably with the increasing of Al₂O₃ content. The Al₂O₃ particles can efficiently resist micro-cutting to protect molybdenum matrix, and therefore enhances the wear resistance of Mo alloy.     

Microstructures and mechanical properties of Er modified AA7075 alloy

The effect of erbium and homogenization on microstructures and mechanical properties of AA7075 alloy were investigated using optical microscope (LIMI), scanning electronic microscope (SEM) equipped with energy dispersive X-ray detection (EDS) and mechanical testing. It was found that during solidification most of the elements Er and Cu segregated at the grain boundaries in the form of Al₃ErCu or Al₈Cu₄Er and a very small part of Er dissolved in the FCC-Al matrix. The latter is not completely reclaimable for heterogeneous nucleation and refine grain FCC-Al matrix in its as-cast state. Er and Cu- containing phases fragmented into fine particles after extrusion and these led to a slight increase in grain boundary strengthening. The process of homogenizing, extruding and aging the Er containing alloys considerably improved the strength due to precipitation. The analysis of the extruded sample showed that the addition of Er can slightly retard the recrystallizing behavior of AA7075 alloy.     

Effect of Al2O3 reinforcement and precipitates on corrosion behaviour of 2618 and 6061 aluminium MMCs

ABSTRACT

The corrosion resistance features of two different Metal Matrix Composites based on 6061 and 2618 aluminium alloys reinforced by 20% Al₂O₃ particles by stir casting process, were studied in 3.5% NaCl and compared. The composites and their respective base alloys were characterised in terms of microstructure by optical and scanning electron microscopy and in terms of corrosion resistance by polarisation curves and electrochemical impedance. Results show how the presence of Al₂O₃ has different effects depending on matrix composition. In 6061 MMC, Al₂O₃ promotes the formation of Mg₂Si which has a cathodic behaviour altering the pitting susceptibility of the composite. In 2618 MMC, the high content of Cu induces a strong uniform attack. The subsequent increase in the Open Circuit Potential caused a pitting attack.     

Filiform corrosion of binary aluminium model alloys

The effect of alloy composition and microstructure on filiform corrosion (FFC) susceptibility was investigated for super-purity based binary model alloys of the systems Al-Mg, Al-Mn, Al-Fe and Al-Cu. Corrosion testing indicated that the presence of electrochemically noble second phase particles is a necessity for FFC to occur. Single phase, solid solution alloys of the Al-Mg, Al-Mn or Al-Fe systems did not support FFC. Heat treatment caused precipitation of the electrochemically noble intermetallic phase FeAl₃ in the Al-Fe alloy, resulting in extensive FFC. Precipitation of the phase MnAl₆, which has electrochemical properties similar to that of the aluminium rich matrix, by heat treatment did not impair the corrosion properties of the Al-Mn alloy. Significant surface oxidation and magnesium enrichment of the surface oxides by heat treatment did not affect the FFC properties of Al-Mg alloys. However, the solid solution binary Al-Cu alloys exhibited severe FFC. The detrimental effect of copper in solid solution is attributable to selective dissolution phenomena during the corrosion process, whereby copper was locally enriched on the surface as copper-rich particles providing efficient cathodic sites.     

High-temperature corrosion of Co-15Mo alloys containing ternary additions of Al in mixed-gas environments

The corrosion behavior of Co-15 at.% Mo alloys containing up to 20at.% Al in gaseous H ₂ -H ₂ O-H ₂ S mixtures was studied over the temperature range of 600–900°C. The corrosion kinetics of all alloys followed the parabolic rate law over the temperature range of interest. Corrosion resistance increased with increasing aluminum content. Complex scales formed on the alloys, consisting of an outer layer of cobalt sulfide and a heterophasic inner layer. Al ₂ O ₃ formed only at high temperatures in alloys having aluminum additions of 15at.% or more. The absence of Al ₂ O ₃ in some cases is due to the small volume fraction of the intermetallic phase CoAl in the alloys and the nature of the slow growth rate of Al ₂ O ₃.Improvement in corrosion resistance is attributed to the presence of a ternary sulfide, Al _0.55 Mo ₂ S ₄,and Al ₂ O ₃ in the inner layer.     

FeCoNiCrCu0.5Alx高熵合金的结构和性能（英文）

研究Al含量和热处理对FeCoNiCrCu0.5Alx多主元高熵合金的相结构、硬度和电化学性能的影响规律。随着Al含量的增加,铸态合金的相结构由FCC相向BCC相转变。当x从0.5增加到1.5时,FeCoNiCrCu0.5Alx高熵合金的稳定结构由FCC结构向FCC+BCC双相结构转变。BCC相的硬度高于FCC相的,在氯离子及酸性介质中BCC相的耐腐蚀性均优于FCC相的。FeCoNiCrCu0.5Al1.0铸态合金具有高硬度和良好的抗腐蚀性能。     

Galvanic Corrosion in Molten Salts: A Discussion of the Corrosion Mechanism of Two-Phase Ni–20Cr–20/30Cu Alloys in Eutectic (Li,K)2CO3 at 650°C

The corrosion of a Ni–20Cr and three ternary Ni–20Cr–Cu alloys containing 10, 20 and 30 wt.% Cu, respectively, in a eutectic (Li, K)₂CO₃ melt was studied at 650°C under air. Ni–20Cr and Ni–20Cr–10Cu are solid-solution alloys, while both Ni–20Cr–20Cu and Ni–20Cr–30Cu are two-phase alloys composed of a Cu-depleted matrix together with a small amount of a Cu-rich phase. The results indicate that Ni–20Cr and Ni–20Cr–10Cu have similar corrosion rates, forming a scale of external NiO and inner Cr-rich oxides. The two-phase Ni–20Cr–20/30 Cu alloys corrode rapidly, producing a mixture of Ni–Cr–rich oxides and a Ni–Cu metallic phase, which may be ascribed to the accelerated corrosion of the Cu-depleted matrix coupled with the cathodic Cu-rich phase of the alloys. As compared to Ni–20Cr–30Cu, Ni–20Cr–20Cu suffers from more-severe corrosion, due to a smaller area fraction of the cathodic Cu-rich phase in the alloy. The galvanic corrosion mechanism is also discussed.     

Ni/Cu定向结构涂层在不同浓度H2SO4中的耐蚀性能

为了研究Cu元素对Ni基合金定向结构涂层耐腐蚀性能的影响,向Ni60合金粉末中添加了5%Cu(质量分数,下同),制备了定向结构Ni60/Cu复合涂层。采用电化学试验和浸泡试验,评估了涂层在不同浓度H₂SO₄溶液中的电化学腐蚀特性和浸泡腐蚀性能,探讨了涂层在不同浓度H₂SO₄溶液中的腐蚀行为。结果表明,涂层在不同浓度H₂SO₄溶液中的腐蚀均表现为活化-钝化-过钝化的过程,电化学阻抗谱在整个时间常数内具有典型的容抗特征,H₂SO₄溶液浓度从5%增至80%时,电荷转移电阻先减小后增大,涂层的耐腐蚀性呈现先降低后升高的趋势。随着H₂SO₄溶液浓度的增加,涂层表面的腐蚀程度先加剧后逐渐减缓,且在H₂SO₄溶液浓度为40%时,腐蚀电位移至最负,腐蚀电流密度增至最大。但在H₂SO₄溶液浓度达到80...