The research on the decomposition and softening-meltingproperties of iron ore by TG-DSC

13 kinds of iron ores （6 from Australia and 7 from Brazil） were studied on their properties concerning CW （Combined Water） decomposition, FezO3 decomposition and softening-melting in air atmosphere through the characterization method of TG-DSC （Thermogravimetry-Differential Scanning Caloremetry ）. The experimental results of the Australian ores and Brazilian ores differ in terms of the initial temperature, temperature range and endothermic amount of CW decomposition,and besides, the content of CW. It is estimated that for every percent increase of CW content in sintering raw material, the extra thermal amount absorbed in the process is about 1.83 x 104 kJ, which equals to the thermal capacity of 0.625 kg of standard coal burning up completely. As to the decomposition of Fe203 ,the initial temperatures, terminal temperatures and temperature ranges of the Australian and Brazilian ores are quite close. However, the endothermic amount of Fe2O3 decomposition of the two turns out rather different： the endothermic capacity of Fe2O3 decomposition of the Australian ores is greater than that of the Brazilian ores. Furthermore, the liquid amount generated in the softening-melting process is closely related to the SiO2 content in iron ore. The higher SiO2 content the ore contains, the more liquid volume it will generate in the softening-melting process of iron ore.

Zirconium-Induced Softening in Hyperstoichiometric Ni_3Al

The room temperature compressive properties and microhardness of Ni3AI alloys doped with Zr were studied. For the hypostoichiometric Ni3AI alloys, the compressive strength and microhardness increased with an increase in Zr content, while softening behavior induced by doping with a certain amount of Zr was observed in hyperstoichiometric Ni3AI alloy. Possible mechanisms for the softening effect were suggested.

Simultaneous enhancement of mechanical properties and corrosion resistance of as-cast Mg-5Zn via microstructural modification by friction stir processing

Magnesium alloys are ideal lightweight materials;however,their applications are extremely limited due to their low strength,poor ductility,and weak corrosion resistance.In the present study,a friction stir processing(FSP)treatment was employed to optimize the mechanical properties and corrosion resistance of an as-cast Mg-5Zn alloy.The average grain size of the Mg-5Zn alloy was refined from 133.8μm to1.3μm as a result of FSP.Along different directions,FSP exhibited the enhancement effects on different mechanical properties.Furthermore,according to the potentiodynamic polarization results,the corrosion current density at the free-corrosion potential of the FSPed sample,was 4.1×10^(-6)A/cm^(2)in 3.5 wt.%Na Cl aqueous solution,which was significantly lower than that of the as-cast sample.Electrochemical impedance spectroscopy revealed that the polarization impedance,Rp,of the FSPed sample was 1534Ω/cm^(2)in 3.5 wt.%NaCl aqueous solution,which was 71.4%greater than that of the as-cast sample.The corrosion morphology of the FSPed sample in 3.5 wt.%NaCl aqueous solution exhibited largely uniform corrosion,rather than severe localized corrosion characteristics,which further reduced the corrosion depth on the basis of reducing the corrosion current density.The results presented herein indicate that FSP is a viable technique for simultaneously improving the mechanical properties and corrosion resistance of the as-cast Mg-5Zn alloy.

灰岩酸蚀裂缝软化区域力学特性与微观特征

碳酸盐岩储层常采用酸化酸压工艺进行改造,酸蚀后岩石表面的微观结构被溶蚀破坏,岩石力学特性发生显著变化,进而影响最终的改造效果。为明确酸蚀对灰岩力学特性和微观孔隙结构变化的影响规律,开展了酸蚀前后灰岩力学特性实验、表面形态特征扫描电镜研究和微观孔隙结构核磁共振表征。结果表明,酸蚀后岩石表面出现了一定厚度的酸蚀软化层,厚度约为11.61μm。值得注意的是,由于酸蚀软化层的存在,灰岩抗压强度、弹性模量与表面硬度均降至酸蚀前的约40%。酸蚀后表层岩石内部产生了大小不一的溶蚀孔洞,并在溶蚀孔洞周边引发应力集中,改变了酸蚀软化层的应力分布。在高闭合应力作用下,溶蚀孔洞易于发生挤压变形或坍塌破坏,这也是酸蚀软化层力学性质改变的主要原因。结合核磁共振T2谱,发现孔径尺寸在1nm~1μm的孔隙数量变化最大,酸液溶蚀改变了灰岩软化层内部的孔隙结构,进而显著影响酸蚀后岩石的力学性质。

冷藏凡纳滨对虾肌肉软化的生化特性及生物标记物

【目的】探究冷藏凡纳滨对虾(Litopenaeus vannamei)质构品质劣变生化变化特性并识别生物标记物。【方法】测定凡纳滨对虾4℃冷藏期间肌肉质构参数,检测肌肉组织中糖原与乳酸含量、ATP水平,以及Ca^(2+)-ATP酶、酸性与碱性磷酸酶(ACP、AKP)活性,分析无氧代谢特征和磷酸化调控酶活性动态变化,解析各指标间相互联系。【结果与结论】4℃冷藏期间对虾质构指标迅速下降,冷藏72 h后硬度显著下降至(2947±113)g(P<0.05),肌原纤维小片化指数(MFI)与质构指标呈显著负相关(P<0.01);新鲜对虾冷藏24 h后磷酸果糖激酶(PFK)活性显著下降至(20.82±0.38)U/mg(P<0.05),且PFK活性与糖酵解各指标相关性最强,其调控的糖酵解是触发和加速肌肉快速软化的关键前期生化事件;ATP含量调控磷酸酶和Ca^(2+)-ATP酶活性,ACP活性和AKP活性在冷藏96 h显著上升至(16.39±1.17)U/mg和(0.86±0.05)U/mg(P<0.05),Ca^(2+)-ATP酶活性24 h后降至(0.50±0.01)U/mg(P<0.05)。随时间延长,Ca^(2+)-ATP酶活性下降诱导内质网释放Ca^(2+)诱导磷酸酶开启去磷酸化进程,蛋白质降解信号暴露被泛素化标记,肌原纤维蛋白进而被降解;相关性分析结合生化基本原理初步判定,Ca^(2+)-ATP酶为质构劣化的生物标记物。

Effect of Ti_(p) Content on the Work Hardening and Softening Behavior of Mg-Zn-Ca Alloy

The Ti_(p)/ZX60 composites with different Ti_(p) contents were prepared by semi-solid stirring casting.After extrusion,the microstructure,work hardening and softening behavior of the Ti_(p)/ZX60 composites were analyzed compared with the ZX60(Mg-6Zn-0.2Ca)alloy.The results showed that the addition of Ti_(p) could not only promote the nucleation of dynamic recrystallized(DRXed)grains,but also be propitious to the refinement of DRXed grains.With increasing Ti_(p) content,the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed grains.As the Ti_(p) content increased to 15 vol.%,the average size and volume fraction of DRXed grains reached to~0.32μm and 93.2%,respectively.Besides,both the strength and elongation were improved by the addition of Ti_(p).With increasing content of Ti_(p),a substantial increase in the strength was achieved with little change in the elongation.However,the elongation decreased sharply when the Ti_(p) content further increased to 15 vol.%.The addition of Ti_(p) led to an increase in the work hardening rate,which gradually increased with increasing Ti_(p) content.However,the softening rate did not demonstrate the same tendency with increasing Ti_(p) content.Unlike the conventional ceramic particles,the Ti_(p) can be deformed in coordination with the matrix alloy,which imparted a higher softening rate to the matrix alloy.Even though the softening rate improved as the Ti_(p) content increased from 5 to 10 vol.%,it dropped deeply as the Ti_(p) content increased to 15 vol.%owing to the fracture of Ti_(p) during extrusion.

热成形钢激光局部软化组织与性能研究

为了降低热成形钢连接位置的硬度,提高塑性,采用高斯激光光束快速扫描试样表面,利用高温回火原理使材料的强度、硬度降低,成功实现了局部区域的材料软化。结果表明,软区组织为回火索氏体,扫描速率越慢,软区硬度越低;温度为800℃、扫描线速率为2 mm/s时,软区硬度为230 HV,是母材硬度的47.92%,软区抗拉强度降低767 MPa,是母材的50.53%,其断后伸长率17.36%,是母材的188.08%;软化拉伸试样为韧性断裂,杯锥状断面;软化后点焊不会改变焊核的硬度,可以加宽热影响区,避免其硬度骤降骤升的情况,改善热影响区应力集中的情况,防止焊点出现界面断裂,软化后能提高焊点断裂最大位移60%,最大能量吸收功提升了10.14%。本研究证明了激光软化热成形钢具有可行性,对热冲压汽车零件局部软化有一定指导意义。

喷气涡流纺汉麻混纺纱及面料的生产

为了开发色织大提花喷气涡流纺细号高混比汉麻纱及其面料,详细分析以渗透剂改善纤维回潮率,以氧化剂降低木质素含量,提升汉麻纤维可纺性及舒适性的原理及方法;以多组分混纺、使用特殊油剂,提升涡流纺纱线柔软度以及纱线强力的具体工艺;在纱线表面被覆柔软剂增加经纱柔韧性,在开口区给湿增加经向股线韧性来提升汉麻混纺纱可织性的方法。通过测试汉麻混纺纱的成纱质量和面料质量,表明:选取15%平平加O渗透剂和0.05 L/kg~0.50 L/kg的臭氧用量对汉麻纤维进行养生处理,使用白油作为润滑剂、二甲基硅油作为防粘剂,纺制的汉麻30/粘胶30/棉40 MVS 14.7 tex混纺纱可批量生产且质量稳定;采用MVS 14.7 tex混纺纱合股、在织机开口区给湿结合经纱柔软剂被覆处理技术后,该汉麻混纺纱面料织造效率高、抗菌性优良;今后应进一步加大细号高混比汉麻混纺纱工艺研究,完善织口加湿技术。

钢轨固定闪光焊接头及母材拉伸性能分析

测试了型式检验不同成套工艺下的钢轨固定闪光焊接头及其母材的拉伸性能,分析了拉伸试样的断裂原因。结果表明:热处理钢轨各部位拉伸强度(Rm和Rp0.2)波动较大,其中轨头最高,但是经过固定焊后的接头各部位拉伸强度趋于一致。钢轨及其固定焊接头的屈强比在0.58~0.63。采用固定焊成型的接头具有优异的拉伸强度,热轧钢轨接头抗拉强度可达到母材的99%~126%,热处理钢轨接头抗拉强度可达到92%~95%。焊后接头的韧性普遍下降明显,接头的断后延伸率(A)占到母材的47%~86%,表明焊接生产工艺尚有优化空间。统计发现,接头拉伸试样一般断在焊缝中心或焊后热处理软化区,如果焊缝没有缺陷,拉伸试样基本都断在软化区,灰斑和MnS夹杂可显著弱化焊缝的拉伸性能。母材的MnS偏析降低了钢轨的焊接性。建议钢厂严格控制钢轨母材轨腰MnS偏析,提高钢轨焊接性;同时建议焊轨厂持续优化生产工艺,减少焊缝灰斑,提高焊接接头的韧塑性。

Effects of various fillers on sintering, microstructures and properties of Ca-Ba-Al-B-Si-O glass/ceramic composites

Low-temperature sintering and properties of LTCC(low temperature co-fired ceramics) materials based on CaO-BaO-Al2O3-B2O3-SiO2 glass and various fillers such as Al2O3, silica glass, christobalite, AlN, ZrO2, MgO·SiO2, TiO2 were investigated. The results show that densification, crystallization, microstructures and dielectric properties of the composites are found to strongly depend on the type of filler. The densification process of glass/ceramic composites with various fillers is mainly from 600 °C to 925 °C, and the initial compacting temperature of samples is 600 °C. The initial rapid densification of samples starts at its glass softening temperature. LTCC compositions containing Al2O3, silica glass, AlN and MgO·SiO2 fillers start to have the crystallization peaks at 890, 903, 869 and 844 °C, respectively. The crystallization peaks are believed as correlated to the crystallization of CaAl2SiO8, β-SiO2, Ca2Al2SiO7 and β-SiO2. The composite ceramic with Al2O3, silica glass and TiO2 ceramic have a better dense structure and better smooth fracture surface. Sample for Al2O3 has the lowest dielectric loss tanδ value of 0.00091, whereas the sample for MgO·SiO2 has the highest dielectric loss tanδ value of 0.02576. The sample for TiO2 has the highest dielectric constant value of 14.46, whereas the sample for AlN has the lowest dielectric constant value of 4.61.

Influence and mechanism of Indonesia vanadium titano-magnetite on metallurgical properties of iron ore sinter

In order to provide a reliable reference for utilizing Indonesia vanadium titano-magnetite(VTM) in blast furnace(BF) economically, metallurgical properties of iron ore sinter with addition of Indonesia VTM in mixed sintering materials were investigated, including low-temperature reduction degradation index(RDI), reducibility index(RI), and softening/melting properties. Additionally, influenced mechanism of Indonesia VTM on metallurgical properties of sinter was studied. It is found that adding Indonesia VTM in sintering process quickly increases the RDI of sinters, and decreases the RI from 78.02% to 68.43%. Moreover, both beginning temperature(T_4) and final temperature(TD) of softening/melting increase gradually, and cohesive zone temperature range(T_D–T_4) enlarges from 219 oC to 315 oC. As a result, the permeability of cohesive zone gets worse, which is proven by the higher maximum pressure drop(δPmax) in softening/melting experiments. It is concluded that, after comprehensively considering all metallurgical properties mentioned above, the proper proportion of Indonesia VTM in sintering process is proposed in the new raw materials conditions.

Compressive Mechanical Properties of Normalized 10^#Low Carbon Steel

Compressive mechanical properties of 10^# lowcarbon steel with normalizing heat treatment are studied. A Gleeble system is adopted to analyze the quasi-static properties and thermal softening effects of heat treated 10^# steel,while a Hopkinson bar apparatus is used to investigate its dynamic characteristics under different strain rates. The results showthat yield stress of heat treated 10^# steel is more than that of untreated one at room temperature. When the specimens are tested at different temperatures,yield stresses decrease with increasing temperature except 573 K. Moreover,the influence of strain rate on yield stress are verified,which shows that the yield stress increases sharply from 500 s^-1 to 1 890 s^-1,while it changes a little from 1 890 s^-1 to 4 850 s^-1. The results indicate that yield stress is mainly influenced by hardening effect at lowstrain rate and controlled by both thermal softening effect and strain rate hardening effect at high strain rate.

Study on Properties of Blue-Brick Masonry Materials for Historical Buildings

There are a large number of historic buildings which were mainly made of blue-brick masonry in today’s world.However,for the natural and man-made reasons,these historic buildings have been damaged in different degrees.In order to protect historic buildings more scientifically and learn about the preservation state of existing historic buildings,it is necessary to ascertain the material properties of blue brick in historic buildings.The article takes the blue bricks of historical buildings in Kaifeng area of the Central Plains as an example to study.Through the analysis of physical properties,X-ray fluorescence spectroscopy,X-ray diffraction and scanning electron microscopy of blue brick specimens,the physical properties such as the apparent density,moisture content,porosity,and material structure composition are understood.The results show that the apparent density of blue brick is 1.64 g/cm^(3),the moisture content is 10.23%,the 24 h atmospheric water absorption is 17.86%,and the porosity is 20.99%.The smaller the apparent density is,the larger the porosity is,and the water absorption performance is better.From the microscopic point of view,bonding ability between blue brick mineral particles is relatively weak.The pores between skeletons are large and the pore structure is obvious.From the perspective of material phase,the elements of blue brick are mainly O,Si,Al,Fe,and the composition of blue brick is mainly composed of quartz and feldspar.The softening coefficient of blue brick is 0.80,and the deformation and stability of the structure should be paid special attention in the rainy season or wet environment.Through the frost test,there are salt substances in the internal pores of the brick,and the surface of the blue brick is eroded and pulverized.In this paper,the experimental process and analysis methods for testing the material properties of blue brick can provide reference for the research on the material properties of the same kind of blue-brick masonry in historic buildings and masonry relics.The relevant material property parameters obtained in this paper can provide guidance for making protection schemes and scientific repairs for historic buildings in Central China,enrich the evaluation criteria for maintaining and reinforcing historic buildings,and provide theoretical support for studying the damage and health detection technology related to historic buildings.

玻璃纤维水泥稳定碎石收缩及柔化抗裂性能研究

为减少沥青路面反射裂缝的产生及扩展,提高沥青路面的整体抗裂性和延长其使用寿命,采用经济效益良好、取材便捷、增韧效果佳的玻璃纤维来改善水泥稳定碎石的收缩及抗裂性能,并通过干燥收缩试验、温度收缩试验、弯曲韧性试验、断裂能试验分析了玻璃纤维对水泥稳定碎石柔化抗裂能力的改善效果。研究结果表明:在玻璃纤维体积掺量为0.05%、0.10%、0.15%时水泥稳定碎石30 d龄期干燥收缩系数分别较普通水泥稳定碎石降低了6%、13%、16%;其平均温缩系数分别降低了6%、16%、19%,玻璃纤维的掺量从0.05%提高到0.10%时平均温缩系数的降低幅度最大,达到了10%,此时的提升效果最佳;3种不同玻璃纤维掺量的水泥稳定碎石的弯拉韧度分别增加了25.9%、48.1%、150.0%,相对于普通水泥稳定碎石,加入0.10%玻璃纤维改性后极限破坏荷载提高了超过20%,破坏时的挠度增大了53%;水泥稳定碎石断裂能增益比达到了1.225。玻璃纤维的加入可以有效抑制水泥稳定碎石材料的干燥收缩和温度收缩变形,同时改性后水泥稳定碎石韧度和破坏时消耗的能量远远大于普通水泥稳定碎石,增强了水泥稳定碎石的收缩和抗裂性能。

海水海砂火山渣混凝土断裂性能试验研究

海洋岛礁工程建设面临着取材困难、运输与材料成本昂贵等问题。为此,开发了新型海水海砂火山渣混凝土(SSAC),以推动海工建设的发展。通过混凝土三点弯曲梁断裂试验,探讨了不同缝高比(0.2、0.3、0.4)和组料类型对SSAC断裂力学性能的影响,获取了双K断裂韧度、断裂能与软化曲线等断裂参数的变化规律。结果表明,受粗骨料的影响,采用火山渣的混凝土的荷载-裂缝口张开位移曲线(P-CMOD)与普通混凝土相似,但其下降段更为陡峭。SSAC断裂韧度小于普通混凝土,且均不受缝高比影响。受海水海砂的影响,SSAC的断裂韧度和断裂能较淡水河砂火山渣试件分别提高14.30%和6.77%。基于试验数据,推导得出考虑组料影响的双K断裂韧度与软化关系计算公式,计算结果与试验结果吻合良好。

基于三轴试验的泥岩力学特性及强度准则研究

研究目的:泥岩在我国有着广泛的分布,其力学性质与其自身含水率有着重要的关系,在各类工程施工中,经常会遇到因泥岩遇水后强度显著降低而引发结构失稳等工程现象。为明确泥岩遇水后强度折减与含水率关系,本文开展不同含水率(0、10.1%、12.5%和14.1%)和不同围压(0 MPa、2 MPa、5 MPa和10 MPa)条件下泥岩三轴压缩试验和间接拉伸试验,以探究适用于软化泥岩的强度准则。研究结论:(1)围压及含水率增大,该泥岩由脆性破坏过渡为延性破坏,其力学性质逐渐接近于正常固结黏土或松砂的特点;围压越高,其强度和弹性模量越大,含水率增高,其强度和弹性模量显著减小,应变增大;(2)泥岩含水率越高,围压对强度的影响作用就越大;低围压环境下(0~2 MPa),泥岩强度随含水率升高而降低的特征较为明显;(3)随着含水率的升高,泥岩抗拉强度和抗剪强度均显著降低,其中抗剪强度中内摩擦角比黏聚力对含水率的变化更为敏感;(4)Rocker强度准则在6种常用强度准则中可更准确地预测不同含水率下泥岩强度,依照该强度准则,提出了考虑含水率效应的软化泥岩非线性强度准则并验证其具有良好的适用性;(5)本研究成果可为各类涉及泥岩的工程提供强度理论依据和工程参考。

不同软化点沥青对天然石墨包覆性能影响

选取3款不同软化点的石油基沥青,以液相包覆法处理天然石墨,对所得样品的粒度、结构、形貌和电化学性能等进行分析。结果表明,软化点为250℃的沥青包覆天然石墨样品表现出最佳的电化学性能,其首次库仑效率由84.70%提高到88.04%,250次循环的容量保持率由63.14%提高到81.19%。低软化点沥青由于炭化时轻组分的释放,包覆层形成大量微孔,导致不可逆容量损失较多;高软化点沥青有利于形成完整包覆层,其对天然石墨的循环性能和倍率性能改善最佳。

压缩荷载下饱和硬岩软化特性与机制研究

环境中的水与岩石的相互作用易导致岩石物理力学性能劣化,即岩石水软化现象。目前,饱和硬岩的水软化特性研究尚不完善,明确各种水岩作用机制的存在条件和作用程度仍是一项挑战性的任务。以不同矿物成分和微结构的典型硬岩(宝兴大理岩、锦屏大理岩、灰岩)为研究对象,进行干燥、饱和状态下3种硬岩的单轴压缩试验和声发射试验,分析硬岩压缩强度、弹性模量、破裂形态等力学特性和声发射波形信号主频统计特征,并探讨了水岩作用机制之孔隙水压力的存在条件和作用程度。结果表明:硬岩饱和后,单轴抗压强度和弹性模量均减小,张拉裂纹和张拉破坏面增多。硬岩破坏的声发射信号表现为明显的、与岩石类型和含水状态无关的双主频特征。硬岩饱和后,声发射高主频带波形信号明显减少,低主频带波形信号显著增加。孔隙水压力是3种饱和硬岩性能劣化的主导因素,其作用强弱与声发射低主频信号多少存在对应关系,且取决于岩石的矿物成分和孔隙结构。

7xxx高强铝合金熔化焊研究进展

针对7xxx高强铝合金的焊接研究现状,主要从TIG,MIG,激光焊及激光-电弧复合焊4类熔化焊工艺进行了介绍;从焊接缺陷、焊缝成形、接头软化、疲劳性能及耐蚀性等方面详述了7xxx高强铝合金熔化焊过程中存在的问题。对于7xxx高强铝合金的TIG,MIG,激光焊及激光-电弧复合焊,焊接缺陷、焊缝成形质量差及接头中强化相熔解等因素都会导致接头发生软化、耐蚀性变差及疲劳寿命降低;通过优化焊接工艺参数,减少焊接缺陷,改善焊缝成形质量,有利于改善接头的软化、耐蚀性差及疲劳寿命低等问题。选用合适的焊丝(含Ti,Zr元素及Er,Sc稀土元素)使焊缝产生沉淀强化、细晶强化及固溶强化,可改善接头软化的问题;采用适当的焊后热处理,改善强化相的尺寸、形态及分布状态,也可改善接头软化的问题;而采用适当的焊后热处理,还可以改善接头的耐蚀性。

竹纤维增强磷石膏板性能试验研究

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