Effect of cobalt addition on microstructure and mechanical properties of tungsten heavy alloys

The present investigation attempts to study the microstructure and mechanical behaviour of tungsten heavy alloys with different cobalt content. Alloys with 2 and 3% cobalt were synthesized using liquid phase sintering technique. The alloys were then vacuum heat treated and finally swaged. Quantitative microstructural analyses were undertaken by determining tungsten grain size, contiguity of tungsten and volume fraction of the matrix etc. Tensile results showed that the alloy with 3% cobalt exhibited inferior properties as compared to 2% cobalt alloy. Detailed microstructural and fractographic analysis were undertaken in order to understand these trends. Work hardening analysis showed the double slope behaviour of the alloys, which could be attributed to change in deformation behaviour from single phase matrix to two phase aggregate. It was also concluded that higher cobalt alloys needed further optimization in terms of thermo-mechanical treatment in order to realize their full potential in terms of mechanical properties.     

增氮对钒微合金钢组织和性能的影响

 通过对不同钒、氮质量分数的试验钢进行热模拟压缩试验和实验室轧制试验,用OM、SEM和TEM分析试验钢的显微组织,研究增氮对钒微合金钢组织和性能的影响。结果表明,普通钒微合金钢为板条贝氏体＋粒状贝氏体组织,增加氮质量分数,可促进晶内铁素体相变,得到针状铁素体组织,使M/A组织细化且弥散分布,改善韧性;而增加钒质量分数,可以增加析出强化作用,提高强度,但组织形态无明显变化,不能提高韧性。增氮钢中的钒在奥氏体内以VN析出,低氮钢内的钒在铁素体内以VC的形式析出,奥氏体-铁素体、VC-铁素体和VN-铁素体的平面点阵错配度分别为6.72%、3.89% 和 1.55%,在奥氏体内析出的VN可以作为铁素体的优先形核位置,促进晶内铁素体相变。     

钒对耐火钢显微组织及高温性能的影响

 通常采用控轧控冷方式生产耐火钢Mo-Nb复合合金化。采用电子显微镜、相分析和三维原子探针等方法,研究了不同热轧工艺条件下钒对含钒耐火钢的室温和600 ℃拉伸性能的影响,探讨了微观组织与力学性能之间的关系。结果表明,添加钒后能形成细小弥散分布的析出物,配合控制贝氏体比例后能有效地提高室温和高温力学性能;钒在热轧态耐火钢中主要固溶于先共析铁素体内,再加热至600 ℃时热轧态被“隐藏”的钒存在明显的析出,进一步提高了含钒耐火钢的高温性能。     

Y2O3含量对钼合金组织和性能的影响

采用粉末冶金方法制备含Y2O3的稀土钼合金,利用金相显微镜、扫描电子显微镜(SEM)、X射线衍射(XRD)、能谱分析(EDS)等手段对钼合金的断裂特征和组织结构进行对比分析,研究稀土氧化物Y2O3含量对钼合金组织和性能的影响.研究表明:添加Y2O3能细化晶粒、改善钼合金的晶粒均匀性和致密度、提高钼合金的性能:拉伸强度和屈服强度随Y2O3含量的增加呈现先增高后降低的趋势,在Y2O3含量为1％时,抗拉强度达511.43MPa,屈服强度456.99MPa,分别是纯钼材料的1.31倍和1.57倍,综合力学性能最佳;在烧结坯中,Y2O3颗粒分布均匀,主要以球形和等轴状形式存在于晶界上.     

Mn含量对Cu-Mn合金结构与性能的影响

基于Cu-Mn中间层可改善Cu与CuCrZr合金的连接性能,采用高能球磨法制备Cu-Mn合金粉末,研究烧结温度为650~850℃、Mn含量(质量分数)为10%~50%的Cu-Mn合金的烧结性能。结果表明:随Mn含量增加,Cu-Mn合金的相对密度和抗拉强度先增大后减小,但Mn含量过高时生成较多的Mn O,导致合金性能下降;随烧结温度升高,合金的相对密度和抗拉强度增大。850℃下烧结的67Cu-33Mn合金孔隙较小、组织均匀,其相对密度和抗拉强度均达到最大值,分别为91.62%和610.91 MPa,表明67Cu-33Mn合金具有最佳的烧结活性,宜作为Cu与CuCrZr合金连接的中间层。     

Effect of homogenization on microstructure and properties of WE91 alloys

The microstructure and properties of the Mg-9Y-1MM-0.6Zr alloy were studied by scanning electron microscopy, optical microscopy, transmission electron microscopy, hardness and tensile testing. Homogeni...     

Effect of microstructure on mechanical properties of as-cast Mg-Al alloys

The mechanical properties of Mg-Al alloys are mainly determined by the microstructure, i.e., the amount and morphology of the phases, but also by the presence of defects arising from the melt handling and casting process. In order to obtain information about the isolated effect of the microstructure, it is, therefore, necessary to minimize the amounts of defects. In this study, this has been achieved by remelting and solidifying the alloys in a gradient furnace. The drawing rate was varied from 0.3 to 6 mm/s, which yielded a wide variety of microstructures. Three samples were produced for each parameter set, in order to have a statistical basis for the evaluation. The results showed that homogeneous and reproducible samples could be produced, and that the tensile properties obtained showed a very small scatter. The effects of microstructural parameters such as grain size, secondary dendrite arm spacing (SDAS), eutectic fraction, and eutectic morphology on the yield strength, ultimate tensile strength (UTS), fracture elongation, and hardness has been investigated.     

氧化锆含量对钼合金组织和性能的影响

采用粉末冶金工艺制备了含不同质量分数氧化锆（ZrO₂）的钼合金棒材,通过拉伸力学性能测试、硬度测试、光学显微镜观察等分析手段,研究了ZrO₂含量对钼合金显微组织和力学性能的影响。结果表明:ZrO₂的添加细化了钼合金晶粒,随着ZrO₂质量分数的增加,钼锆合金的硬度和室温抗拉强度增加。当ZrO₂质量分数为2.5%时,钼锆合金的硬度达到最大值（HV₁₀ 240）,抗拉强度达到最大值（820 MPa）。     

Effect of manganese addition on the microstructure and electromagnetic properties of YIG

Y3MnxFe4.85-xO12 (x=0, 0.02, 0.04, 0.06, 0.08 and 0.1) garnet ferrites (YMnIG) were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and electromagnetic properties of YIG were investigated by means of techniques such as X-ray diffraction, scanning electron microscopey, network analyzer, hysteresigraph, magnetic balance and electron paramagnetic resonance spectrometry. Pure garnet phase of Y3Fe5O12 was identified for all the samples, except for minor YFeO3 phase appearing in the sample with x=0.06. The addition of Mn showed little influence on the dielectric constant of YIG, which varied between 14.2 and 14.5. Substituting Mnn+ for Fen+ in YIG decreased the total amount of Fe ions, inhibited the reduction of Fe3+ and promoted the grain growth of garnet phase, which led to the decrease in dielectric loss and coercivity. Because the amount of Mn3+ ions in octahedral sites in- creased with Mn concentration, the saturation magnetization showed a slight decrease firstly and then increased notably. The addition of Mn could also increase the remanence ratio of YIG ferrites by decreasing the magnetostriction constant λ111. Therefore, doping Mn into YIG fer- rites with proper quantity could improve electromagnetic properties of YIG significantly. The YMnIG ferrite with x=0.08, i.e., Y3Mn0.08 Fe4.77O12, showed the optimum electromagnetic properties: εr=14.2, tanδe=1.5×10-4, Hc=36 A/m, 4πMS=192 mT, Br/Bs=0.84, ?H=6.8 KA/m.     

Effect of cerium addition on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

Effect of cerium addition on the microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy have been investigated. In this study, aluminum alloys with up to 0.4% cerium content have been prepared by melting, metal mould casting followed by thermo-mechanical processing. The alloys were extensively characterized by optical and transmission electron microscopy, followed by mechanical property examination by tensile tests as well as nanoindentation tests. It was observed that cerium addition results in up to 5% grain refinement of the cast dendritic structure as well as up to 38% refinement of the heat treated microstructure. Transmission electron microscopy (TEM) has revealed the uniform distribution of fine GP zones and some semi coherent β(MgZn₂) precipitates in the Al rich matrix. Further TEM results show that when the Ce content was changed from 0.1% to 0.4%, precipitate size increased from 5 to 50nm and the precipitate morphology changed from spherical to needle shape. Evaluation of mechanical properties through tensile and nano-indentation tests have exhibited that both Young’s modulus and tensile strength increases with Ce addition up to 0.3% and subsequently decrease.     

配加铁矿粉对铁焦微观结构及性能的影响

 为了研究在炼焦过程中配加铁矿粉对焦炭性能的影响,在气煤中配加0、5%和10%的铁矿粉炼制铁焦,采用I-型转鼓、差热分析仪、SEM、XRD和光学显微镜对铁焦的强度、反应性、微观结构、微晶结构和光学组织进行研究,并采用Coats-Redfern方法计算气化反应的动力学参数。结果表明,在气煤中配加铁矿粉可以有效提高铁焦的转鼓强度及反应性,随着铁矿粉配比的增加,铁焦的堆垛高度[Lc]值逐渐减小,石墨化程度降低,并且铁焦的气孔逐渐减小,且附着于气孔表面的铁原子密度增大,出现成片含铁区域,焦炭结构中各向同性结构和镶嵌结构减少,残炭结构增多。根据动力学分析可知,配加0、5%和10%的铁矿粉制得的铁焦,其活化能分别为228.4、235.5和256.7 kJ/mol,并且发现表观活化能与指前因子具有动力学补偿作用。     

添加氧化锆对硬质合金组织和性能的影响

研究了添加不同质量分数的非稳定态钇氧化锆ZrO2（摩尔分数为3%Y2O3）对硬质合金组织和性能的影响,并对金相组织和性能的理化检测结果进行了分析研究.结果表明：在烧结体中,通过控制添加的非稳定态钇氧化锆ZrO2（3%Y2O3）重量比例可以使硬质合金的组织稳定,在不降低硬度的前提下,使硬质合金的抗弯强度得到提高.     

Effect of magnesium addition on microstructure and mechanical properties in wheel steel

In order to reveal the effect of Mg in low carbon microalloy steel, low carbon microalloy steel of HR60 wheel steel was smelted in vacuum induction furnace and industrial field respectively. The characteristics of typical non- metallic inclusions and microstructure of experimental steels were both compared by OM, SEM- EDS and INCA Feature with automatically scanning inclusions function. The mechanical properties of the experimental steels were also measured. The results show that alumina inclusions are modified to spinel inclusions with small size after Mg addition. Furthermore, acicular ferrite can be induced effectively by inclusions containing magnesium. The microstructures of experimental steels are changed from ??polygonal ferrite(PF) + pearlite(P)??to ??polygonal ferrite(PF) + degenerate pearlite(DP) + acicular ferrite(AF)?? and refined by Mg treatment. The strength of experimental steels is improved with Mg addition. In industrial experiments, the fatigue limit of Mg- treated steels is greater than 460MPa, while the fatigue limit of Ca- treated steels is about 450MPa. In addition, the fatigue life of Mg- treated steels is generally higher than that of Ca- treated steels under the condition that the stress is greater than the fatigue limit. In laboratory experiments, the contents of Nb and Ti are reduced while Mg content in steel is 18??10-6, the strength of the wheel steel is close to the reference steel. Therefore, the project to reducing production cost by taking advantage of the microalloy role of Mg is feasible.     

稀土Pr对Al-Zn-Mg-Cu-Zr合金组织和性能的影响

采用铸锭冶金法制备含稀土元素Pr的Al-Zn-Mg-Cu-Zr合金,并通过金相分析以及拉伸性能、晶间腐蚀和剥落腐蚀性能的测试研究价格相对低廉的Pr对Al-Zn-Mg-Cu-Zr合金显微组织、力学性能和腐蚀性能的影响.结果表明,添加稀土元素Pr能影响合金铸态组织中第二相的析出,并显著抑制合金在变形和热处理过程中再结晶的发生,在保持合金的强度及弹性模量的同时,改善合金抗晶间腐蚀和剥落腐蚀的性能,并提高合金的塑性.     

Effect of addition of nitrogen on the microstructure and properties of cold-forged-roll steels

The heat-treatment characteristics,mechanical properties,and wear behavior of four cold-forged-roll steels were studied and their microstructural characteristics were analyzed using transmission electron microscopy(TEM),scanning electron microscopy(SEM),X-ray diffractometer(XRD),and an oxygen-nitrogen analyzer.The results show that the introduction of nitrogen facilitates improvement in the mechanical properties of cold-forged rolls.A solid-solution strengthening effect is obtained by interstitial nitrogen,and the hardenability of rolls can be improved as well.A significant effect on grain-size refinement is obtained by highly thermally stable fine M(C,N)carbonitrides,which pin the grain boundaries during austenitization and block the growth of austenitic grains.Compared to conventional roll steels,the optimum quenching temperature of steel with added nitrogen can be increased by 20-30℃ Therefore,the hardening temperature range is expanded,which is beneficial to the heattreatment process.Furthermore,high-hardness carbonitrides can improve the wear performance.     

微量合金元素添加对Al2O3弥散强化Cu微观组织和硬度的影响研究

弥散强化Cu是一种广泛应用于汽车和电子行业的高强高导Cu基复合材料。本文采用机械合金化法制备了Al2O3颗粒弥散强化Cu合金,并对比研究了微量Ag、Ni、Zr、Hf和Ti合金元素对Cu-1.20%Al2O3弥散强化Cu合金微观组织和硬度的影响。XRD结果表明高能球磨能有效地固溶Al2O3弥散相到Cu基体中;硬度测试表明添加Ag元素能显著地提高弥散强化Cu的维氏硬度,添加Ni和Hf元素仅在一定程度上改善弥散强化Cu的维氏硬度,而添加Zr和Ti元素则对提高弥散强化Cu的硬度作用不大;SEM表征结果显示有Ag掺杂的弥散强化Cu合金中的Al2O3弥散相粒径明显小于未掺杂Ag的情况。弥散强化Cu硬度的提高与Ag在Cu与Al2O3相界面的偏聚进而有效抑制弥散Al2O3颗粒长大紧密相关。     

Fe2O3对粉末冶金铁基合金组织和力学性能的影响

在气雾化Fe-12Cr-2.5W-0.4Ti-0.25Y粉末中添加1％(质量分数)的Fe2O3粉末,经过热挤压-轧制-热处理工艺制得铁基合金,研究添加Fe2O3对铁基合金显微组织和性能的影响.结果表明:添加少量Fe2O3粉能促进合金中粒径为200 nm到5μm的富Ti、Y、Cr和O的第二相颗粒形成;第二相颗粒能够显著细...     

Effect of lanthanum addition on microstructure and hardness of brass alloys produced by rheological squeeze casting

The effect of La addition (0–0.30 wt%) on the microstructure and hardness of rheological squeeze casting brass alloys was experimentally investigated. The rheological squeeze casting process is improved by controlling the wall surface crystals and melt flow rate to realise the preparation of semi-solid melt with flow, and a brass alloy workpiece with La is produced. The microstructure and properties of the brass alloy samples were investigated using metallography, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and hardness testing. The results indicate that the hardness of the rheological squeeze casting brass alloy is increased by 20.4% from 108 to 130 HBW with an increase in the La content from 0 to 0.30 wt%. The microstructural analysis results show that La significantly refines the primary α-phase grains, and the main mechanism is the constitutional undercooling and heterogeneous nucleation caused by the La enrichment in the front of the solid–liquid interface. The squeeze pressure promotes undercooling, which improves the nucleation rate and affects the solute diffusion and nucleus growth. The dual effects of these two aspects aggravate the grain refinement process, consequently increasing the number of grain boundaries and improving the hardness of the brass alloy.     

制备工艺对粉末高钒高速钢组织和力学性能的影响

采用传统熔炼工艺和粉末冶金工艺制备钒含量10%的高钒高速钢,并通过金相组织观察、硬度和冲击韧度的测量来研究制备工艺对高钒高速钢组织和力学性能的影响。结果表明:熔炼高钒高速钢碳化物粗大、分布不均,在冲击过程中大颗粒碳化钒易碎裂;而通过氮气雾化制粉+热等静压工艺,采用粒度小于50μm的细粉后,碳化钒颗粒细小(3μm)且分布均匀,在冲击过程中不易破碎,冲击吸收功达到42 J/cm2,断裂机制以碳化钒与基体的界面失效为主。