合金元素对Al-Si合金力学性能及组织的影响

采用正交试验方法研究Ni、Cr及Zn三种合金元素对Al-7.5Si-3.5Cu-0.35 Mg亚共晶铸造铝硅合金力学性能影响,并用SEM和EDX对加入微量合金后的铸态组织进行观察与分析。结果表明,最优配比为Ni0.02Cr0.03Zn0.2。在合金铸态组织中,Ni、Cr、Zn元素形成复杂的灰白色短棒状或粒状ω相,中和了Fe的有害作用,并且在合金拉伸变形时,可以阻碍位错的运动,对合金基体有一定的强化作用。     

纳米晶Al-Cu-Mg合金的微观组织与力学性能研究

以工程实际中应用较广的Al-Cu-Mg铝合金作为研究对象, 用Al-Cu-Mg铝合金气体雾化粉末作为原材料, 通过低温液氮球磨获得纳米晶后, 再经真空热压和热挤压制备了致密的大块体纳米材料. 通过力学性能测试, 挤压态的纳米晶Al-Cu-Mg块体材料抗拉强度达470 MPa, 经过T4处理后, 抗拉强度达到590 MPa, 远远超过常规方法制备的Al-Cu-Mg铝合金抗拉强度. 对纳米晶Al-Cu-Mg块体材料进行微观组织观察, 分析了材料强度提高的原因.     

纳米晶Fe-Si合金粉末的微结构及磁性能研究

通过高能球磨法制备Fe75Si25纳米晶合金粉末，研究了高能球磨下的反应进程及产物，并讨论了合金粉末的微观结构和磁性能。结果表明：对于Fe75Si25粉末，合金化得到的是bee晶体结构的α-Fe（Si）固溶体。球磨84h以后，晶粒度达到了18nm，并且合金化程度较高。合金粉末具有良好的软磁性能，粉末的磁导率和比磁化强度，随着球磨时间的增加呈先减小后增大的趋势。热处理温度对粉末磁性能有着较大的影响，在380℃左右合金粉末的磁性能最好。     

铁基多元纳米晶合金的微组织和软磁性能

研究了新近开发的纳米晶（Fe90Zr3.5Nb3.5B3）95Cu1Si4合金的微组织和软磁性能.采用XRD、TEM和Mssbauer谱仪观察了合金的微组织变化,采用直流软磁测量设备测量了软磁性能.结果显示,合金是纳米晶相、残余非晶相和中间相的混合.软磁性能随着退火温度的变化而变化,且中间相的体积分数会影响软磁性能.当813K退火0.5h后,纳米晶相体积分数为40%,软磁性能最佳,此时BS最大为1.56T,HC达到最小为1.79A/m.     

C添加对近β钛合金显微组织及性能的影响

研究了在不同热处理条件下C元素的添加量对近β钛合金Ti-4Al-5Mo-8V-2. 5Cr-1Sn-2Zr微观组织及力学性能的影响。结果表明:C元素添加对近β钛合金在不同热处理条件下的微观组织均有显著影响。C元素添加会导致β晶粒的细化,当C元素添加量由0%(体积分数,下同)增加到3%时,固溶处理后合金的β晶粒尺寸由137μm降低至25μm,且尺寸更加均匀。当C元素添加量持续增加时,β晶粒开始长大。经时效处理后,随着C元素添加量的增加,次生α相尺寸和体积分数均减小。相比于单级时效,双级时效呈现出更多的次生α相。此外,单级时效后晶界处的次生α相会随着C元素添加量的增加而逐渐消失。由于受晶粒细化、TiC颗粒和次生α相的影响,随着C元素添加量的增加,合金的显微硬度和拉伸强度明显提高,塑性降低。     

激光熔化沉积Cu-Fe合金的液相分离组织及力学性能研究

难混溶合金由于亚稳难混溶间隙的存在,在制备过程中极易产生偏析甚至分层现象,严重影响材料的使用性能。激光熔化沉积小熔池无宏观偏析的特点,为制备均质难混溶合金提供了潜在途径。本文选取典型难混溶Cu-Fe合金作为研究对象,采用激光熔化沉积制备了薄壁状Cu35Fe65难混溶合金,研究了合金的物相组成、微观组织形貌与力学性能。结果表明：合金由体心立方（bcc）结构的α-Fe相与面心立方（fcc）结构的Cu相组成;合金呈现典型的液相分离形貌,由网络状Cu相与块状α-Fe相构成,α-Fe相平均直径为8 μm;合金屈服强度为397 MPa,抗拉强度为484 MPa,延伸率为16.5%,断裂方式主要为韧性断裂;合金的导电率为19% IACS,较高的α-Fe相体积分数可能是影响合金电阻率的主要因素。本研究表明,激光熔化沉积技术有望成为高性能难混溶合金的有效制备方式。     

Ti90及其优化合金的组织与力学性能研究

Ti90合金是我国自主研发的一种新型近α型钛合金,具有高比强度、高韧性、耐蚀和加工性能好等优点。本课题组前期对Ti90合金进行了成分优化,得到一种名义成分为Ti-5. 5Al-4. 0Zr-1. 0Sn-0. 3Mo-1. 0Nb的优化合金。利用X射线衍射仪、金相显微镜、电子探针显微分析仪、电子万能试验机和电化学工作站等检测仪器,对Ti90及其优化合金的组织与力学性能进行对比分析。结果表明,优化合金组织为带有网篮特征的魏氏组织,原始β晶界和α集束清晰可见,有少量残留β相分布于α片层之间。与Ti90合金相比,优化合金的压缩屈服强度与断裂韧性得到了显著的提高,极限应变量有所增加,电化学腐蚀性能较好。     

Microstructures and Properties of Nanocrystalline NiFe Alloy With and Without Particulate TiC Reinforcement by Mechanical Alloying

In the current study, Ni₅₀Fe₅₀ alloy powders were prepared using a high-energy planetary ball mill. The effects of TiC addition (0, 5, 10, 20, and 30 wt pct) and milling time on the sequence of alloy formation, the microstructure, and microhardness of the product were studied. The structure of solid solution phase, the lattice parameter, lattice strain, and grain size were identified by X-ray diffraction analysis. The correlation between the apparent densities and the milling time is explained by the morphologic evolution of the powder particles occurring during the high-energy milling process. The powder morphology was examined using scanning electron microscopy. It was found that FCC γ (Fe–Ni) solid solution was formed after 10 hours of milling, and this time was reduced to 7 hours when TiC was added. Therefore, brittle particles (TiC) accelerate the milling process by increasing crystal defects leading to a shorter diffusion path. Observations of polished cross section showed uniform distribution of the reinforcement particles. The apparent density increases with the increasing TiC content. It was also found that the higher TiC amount leads to larger lattice parameter, higher internal strain, and lower grain size of the alloy.     

Bi对AZ81镁合金组织和力学性能的影响

通过合金制备、微观分析和拉伸试验等方法,研究了Bi对AZ81镁合金组织和力学性能的影响。结果表明:在AZ81中加入适量的Bi后,细化了合金的铸态组织,同时基体中出现热稳定性较高的颗粒相Mg3Bi2。适量Bi的加入提高了合金的室温和高温力学性能,改善了合金的耐热性能。     

微量添加晶界合金对烧结Nd-Fe-B力学性能及微观结构的影响

采用双合金法制备系列烧结Nd—Fe—B磁体(保持其主合金成分不变：Ndl4．1Dy0．5Fe79.0B6.4(原子分数)，所添加的晶界合金中的B含量从0．95％(原子分数)逐步增加到6．95％(原子分数))，研究了微量添加晶界合金对烧结Nd—Fe—B力学性能及微观结构的影响。研究结果表明：微量添加晶界合金所制备的磁体，其抗弯强度值普遍高于单合金法制得的磁体；前者的抗弯强度最高可达397MPa，高于铸造，热压磁体的抗弯值，而后者的抗弯强度仅为309MPa。由相结构分析可知，当添加的晶界合金中的B含量为O．95(原子分数)，主相晶格的四方度减小，这时磁体具有最高的抗弯强度。另外，微量添加晶界合金，可使磁体中晶界相的分布更加均匀，从而基本上消除了主相晶粒直接接触的现象，使晶粒的不规则长大得到抑制。这也是微量添加晶界合金后磁体具有较高抗弯强度的原因之一。对磁性能的研究结果表明，微量添加晶界合金几乎不影响烧结Nd—Fe—B磁体的磁性能。     

Al-Ti-B对AZ91D镁合金显微组织和力学性能的影响

研究了Al-Ti-B对AZ91D镁合金铸态显微组织和力学性能的影响，并探讨其化学成分与组织结构和力学性能之间的变化。研究结果表明：Al-Ti-B加入AZ91D镁合金，能明显细化组织晶粒，从而改善合金的室温力学性能。当加入Al-Ti-B时，合金晶粒细化效果较好，其室温力学性能和硬度比原来都有较大的提高。     

Ti60高温钛合金环材组织与性能的研究

研究了Ti60高温钛合金环材的组织和性能。结果表明,该合金环材经双重退火后的显微组织为双态组织,并含有强化相α2相及硅化物相;这种组织的环材具有良好的室温拉伸、高温拉伸、热稳定、蠕变和断裂韧性等性能匹配,它的各项主要性能与IM I834钛合金相当,可用于制作航空发动机压气机压气盘、叶片等构件。     

Effect of Pulsed Magnetic Field on Microstructure and Mechanical Properties of Eutectic Al-Si Alloy

Pulsed magnetic field (PMF) processing has been employed for refining the microstructure of eutectic (Al-12.4Si) Al-Si alloy in the current study. The effect of PMF on microstructure and mechanical properties of eutectic Al-Si alloy was studied. The results show that the morphology of primary α-Al was refined from coarse columnar dendrites to fine equiaxed dendrites by PMF treatment. Fine short rod-like or rounded particle-like eutectic silicon was formed during solidification of eutectic Al-Si alloy treated by PMF. PMF treatment reduced the size of eutectic silicon from 49 to 2.3 μm in length, and the width from 3.1 to 0.6 μm. The aspect ratio of eutectic silicon was also reduced by PMF treatment from slightly less than 16 to slightly less than 4. The ultimate tensile strength and elongation of eutectic Al-Si alloy with PMF treatment at room temperature were about 201 MPa and 8.8 pct, respectively, which were increased by 47 and 73 pct, respectively, compared with the eutectic Al-Si alloy without PMF treatment.     

热处理工艺对Ti53311S钛合金组织与性能的影响

研究了低温退火和高温淬火＋时效两种热处理方式对Ti53311S钛合金棒材显微组织与力学性能的影响。实验结果表明：经两种不同热处理制度处理后,均能获得满足Q／XB1517—1998标准要求的Ti53311S钛合金棒材。经650oC低温退火处理后可获得等轴a＋β组织,经高温淬火＋时效处理后可获得等轴初生a＋含针状a的转变β双态组织。在生产中,可根据实际情况选取更为适宜的热处理方式,其中,较为经济的热处理方式为650℃×60min／AC;可获得较好力学性能的热处理方式为980℃×（30～90）min／WQ＋650℃×6h／AC。     

Effect of Yttrium and Cerium Addition on Microstructure and Mechanical Properties of AM50 Magnesium Alloy

To develop magnesium alloy with low cost, high strength and excellent elevated temperature properties, effect of Y and Ce addition on microstructure and mechanical properties of AM50 magnesium alloy was studied. Result showed that addition of small amount of Y and Ce to AM50 alloys resulted in refinement of microstructure. Owing to the improvement of microstructure, the mechanical properties of alloys at both ambient and elevated temperature were increased. AM50 alloy containing 0.6 % Ce-0.3 % Y （mass fraction） had good refinement effect and relatively ideal mechanical properties.     

热加工对Ti53311s钛合金显微组织和力学性能的影响

Ti53311s合金是一种适于550℃使用的耐热钛合金,本文对该合金在不同热加工条件下的显微组织进行了研究。结果表明,Ti53311s合金在β→α＋β转变温度以下,经单向拔长锻造的棒材的室温、高温性能与镦拔锻造的棒材相当。     

机械合金化制备Fe-Si-Al软磁合金的研究

采用机械合金化制备Fe85-Si9. 5-Al5. 5合金粉末, 利用金相仪、激光粒度分析仪、 SEM和XRD研究了球磨时间及烧结工艺对Fe-Si-Al合金断裂形貌、微观组织及力学性能的影响. 试验结果表明, 将球磨10 h的复合粉末冷压成形后, 烧结温度为1350 ℃, 保温2 h, 可获得综合性能最佳的Fe-Si-Al合金, 致密度达99.6%、抗弯强度为801 MPa, 硬度为65.68HRA.     

Effect of Nanocrystalline Powders on the Structure and Properties of Dispersion-Hardened Alloy TiC – 40% KhN70Yu

This article examines aspects of the effect of nanocrystalline powders of ZrO₂, Al₂O₃, W, WC, WC–Co, NbC, and Si₃N₄ on the combustion, structure, and physical and physico-mechanical properties of new dispersion-hardened electrode alloy TiC – 40%KhN70Yu. This heat-resistant hard alloy, based on titanium carbide and a nickel alloy, was obtained by self-propagating high-temperature synthesis (SHS). It is shown that the addition of a nanocrystalline powder decreases combustion rate, with the magnitude of the reduction depending on the specific surface of the addition. It was determined that the structure of the synthesis products is modified appreciably by introducing a mixture of nanocrystalline powders into the initial charge. Here, additions of ZrO₂ and NbC have a positive effect on the main physico-mechanical characteristics of the alloy (strength, hardness, fracture toughness). Nano-powders of Al₂O₃ and Si₃N₄ have a negative effect on the alloy's physico-mechanical properties. The addition of WC–Co increases the flexural strength of the material, while the addition of W and WC increases its fracture toughness.     

Microstructure and Mechanical Properties of Nanostructured Al-4Cu Alloy Produced by Mechanical Alloying and Vacuum Hot Pressing

Bulk nanostructured Al-4 wt pct Cu alloy with high compression strength (879 MPa) was produced by mechanical alloying followed by vacuum hot pressing (VHP). The hot-pressed compacts were nanostructured with a grain size of 50 nm and were densified to more than 99 pct of the theoretical density. Contributions from different strengthening mechanisms were estimated using simplified models and were compared with the experiment.