Influence of Pressing Time on Steel-copper-graphite Bonding

The bonding of steel plate with QTi3.5-3.5 graphite slurry was studied by using pressing bonding technique. The influence of pressing time on the interracial mechanical property of bonding plate was researched. The results show that： under the conditions of 620℃ preheating temperature of steel plate, 530℃ preheating temperature of dies, 46% solid fraction of QTi3.5-3.5 graphite slurry and 50 MPa pressure, there exists a nonlinear relationship between pressing time and interracial shear strength. The interracial shear strength of bonding plate increases with increasing pressing time and reaches a largest value about 127 MPa when pressing time is longer than 120 s. At the interface with the best mechanical property, there exists a continuous Fe-Cu inter-diffusion zone and a metallurgical bonding.     

Effect of Relative Reduction on Property of Steel-Mushy Cu-Graphite Composite

The rolling treatment of steel-mushy QTi3.5-3.5 graphite composite was conducted under different relative reduction at room temperature. The effect of room-temperature rolling on interfacial mechanical property of steel-mushy QTi3.5-3.5 graphite composite was studied and the relationship between interfacial shear strength and relative reduction was established. The results show that, for steel-mushy QTi3.5-3.5 graphite composite, which consists of 1.2 mm-thick 08AI steel plate and 2.8 mm-thick QTi3.5-3.5 graphite layer, there is a nonlinear relationship between interfacial shear strength and relative reduction in graphite layer. When relative reduction is smaller than 1.1%, interfacial shear strength increases with increasing the relative reduction. When relative reduction is larger than 1.1%, interfacial shear strength decreases with increasing the relative reduction. When relative reduction is 1.1%, the largest interfacial shear strength of 145.2 MPa can be obtained.     

Preparation QT3.5-3.5 graphite lubricant material with semi-solid casting technology

For the first time, the distribution of graphite particles in QTi3.5-3.5 graphite ingot was studied by using semi-solid casting technology. The results show that: the relationship between solid fraction and stirring temperature of QTi3.5-3.5 graphite slurry is y=759.4-0.711x (where y is solid fraction, x is stirring temperature). With the increasing of solid fraction of QTi3.5-3.5 graphite slurry, the agglomeration of graphite particles in ingot reduces gradually. The condition to prepare QTi3.5-3.5 graphite lubricant material with even distribution of graphite particles is that the solid fraction of QTi3.5-3.5 graphite slurry is larger than 40%.     

Preparation QTi3.5-3.5 Graphite Lubricant Material with Semi-solid Casting Technology

For the first time, the distribution of graphite particles in QTi3.5-3.5 graphite ingot was studied by using semi-solid casting technology. The results show that: the relationship between solid fraction and stirring temperature of QTi3.5-3.5 graphite slurry is y=759.4-0.711x (where y is solid fraction, x is stirring temperature). With the increasing of solid fraction of QTi3.5-3.5 graphite slurry, the agglomeration of graphite particles in ingot reduces gradually. The condition to prepare QTi3.5-3.5 graphite lubricant material with even distribution of graphite particles is that the solid fraction of QTi3.5-3.5 graphite slurry is larger than 40%.     

Influence of Solid Fraction on Structure of QTi3.5-15/Graghite Slurry

The electromagnetic-mechanical stirring technology was used to prepare QTi3.5-15/graghite slurry. The distribution of graphite particies in QTi3.5-15/graghite slurry was studied using cold quenching method. The results show that solid fraction of QTi3.5-15/graphite slurry increases with the decreasing of stirring temperature. There is a linear relationship between solid fraction and stirring temperature. With the increasing of solid fraction, the distribution of graphite particies in slurry becomes uniform gradually. When the solid fraction is larger than 45%, the rising of graphite particies in slurry can be restricted, and QTi3.5-15/graghite slurry with uniform distribution of graphite particies can be prepared.     

Study on Steel-Mushy Al-20Sn Alloy Bonding

Steel-mushy Al-20Sn alloy bonding was studied for the first time. The relationship model about preheat temperature of steel plate, solid fraction of Al-20Sn alloy mushy, rolling speed and interfacial shear strength of bonding plate could be established by artificial neural networks perfectly. This model could be optimized with a genetic algorithm. The optimum bonding parameters were: 505℃ for preheat temperature of steel plate, 34.3% for solid fraction of Al-20Sn alloy mushy and 10 mm/s for rolling speed, and the largest interfacial shear strength of bonding plate was 71.2 MPa.     

Interfacial Structure of Steel-Mushy Al-20Sn Bonding Plate

Fe-AI compound at the interface of steel-mushy AI-20Sn bonding plate was studied quantitatively. The relationship between ratio of Fe-AI compound at interface and bonding parameters (such as preheat temperature of steel plate, solid fraction of AI-20Sn slurry and rolling speed) was established by artificial neural networks perfectly. The results show that when the bonding parameters are 505℃ for preheat temperature of steel plate, 34.3% for solid fraction of AI-20Sn slurry and 10 mm/s for rolling speed, the reasonable ratio of Fe-AI compound corresponding to the largest interfacial shear strength of bonding plate is obtained. Its value is 72%. This reasonable ratio of Fe-AI compound is a quantitative criterion of interfacial embrittlement, that is, when the ratio of Fe-AI compound at interface is larger than 72%, interfacial embrittlement will occur.     

铜-石墨复合材料的半固态铸造研究

首次采用半固态加工方法对QTi3.5-3.5石墨复合材料进行了研究,得到了半固态浆料固相率与铸锭中石墨颗粒分布之间的关系,确定了获得石墨颗粒均匀分布的QTi3.5-3.5石墨复合材料的半固态加工技术条件。结果表明,随着半固态浆料固相率的增大,石墨颗粒的上浮偏聚程度逐渐减小,当采用固相率大于40%的半固态浆料进行铸造时,石墨颗粒的上浮偏聚现象得以消除,可获得石墨颗粒均匀分布的QTi3.5-3.5石墨复合材料。     

Influence of Rolling Treatment on Interfacial Shear Strength of Steel-mushy Al-7graphite Bonding Plate

At room temperature, the rolling treatment of steel-mushy Al-7graphite bonding plate was carried out under different relative reduction. The influence of rolling on interfacial mechanical property of this bonding plate was studied. The results show that, for steel-mushy Al-7graphite bonding plate which is made up of 1.2 mm in thickness 08AI steel plate and 2.0 mm in thickness Al-7graphite layer, there is a nonlinear relationship between interfacial shear strength of bonding plate and relative reduction of rolling. When relative reduction of rolling is smaller than 2.59%, with the increasing of relative reduction, interfacial shear strength of bonding plate increases gradually. When relative reduction of rolling is bigger than 2.59%, with the increasing of relative reduction, interfacial shear strength of bonding plate decreases continuously. When relative reduction of rolling is 2.59%, the largest interfacial shear strength 77.0 MPa can be obtained.     

Fractals in Steel-Aluminum Solid to Liquid Bonding

1.IntroductionSinceBenoitMandelbrotpresefltedfrartalthe-oryinhisbook<>inl977formally,itcanbesaidthatthestudyandapplicationoffractalshadbeencon-ductedinalmosteveryfieldgenerallyformorethan2oyears.On1yformetalfracturefield,greatevolutionandprogresshavebeenacquired,thegeneralrulesarethatalthoughthefracturesurfaceisscraggyandirreg-ular,ithasobviousselfanaloguecharacteristicwhenitisobservedwithinsomerealmofsize[1'2].There-foretheirregularityofthefracturesurfacecan…     

钢-Al-20Sn复合板的非均匀扩散复合研究

提出了消除钢-Al-20Sn复合板复合界面脆化的非均匀扩散思想,并采用Al-20Sn半固态浆料与钢板进行铸轧复合,实现了非均匀扩散,改变了复合界面结构,消除了复合板复合界面的脆化。研究结果表明,在500℃钢板预热温度、10mm/s铸轧速度条件下,当半固态浆料固相率为34.3%时,复合界面由比例恰当的铁铝化合物和铁铝固溶体交替构成,脆化得以消除,相应的最大界面剪切强度为69.9MPa。     

Study on Mechanical Property in Steel-Aluminum Solid to Liquid Bonding

The bonding of solid steel plate to liquid Al was conducted using rapid solidification.The influence of thickness of FeAl compound layer at the interface on interfacial shear strength of bonding plate was studied.The results show that the relationship between thickness of Fe-Al compound layer and interfacial shear strength is S=30.4 8.51 h-0.51h^2 0.007h^3(where h is thickness of Fe-Al compound layer,S is interfacial shear strength).When thickness of Fe-Al compound layer is 10.7μm,the largest interfacial shear strength is 71.6MPa。     

激光多层熔覆纳米陶瓷层工艺参数优化

为了深入了解激光多层熔覆工艺与涂层性能之间的关系,采用压片预置式激光多层熔覆工艺制备了纳米Al2O3-13%TiO2(质量分数)陶瓷层;通过3因素3水平正交试验分析了激光熔覆熔池闭环控制温度、超声振动频率及保温箱预热温度对涂层结合强度的影响,并对激光熔覆工艺参数进行了优化;通过扫描电镜(SEM)和结合强度测试研究了最优工艺下所得涂层的形貌和性能。结果表明:影响涂层结合强度的因素主次顺序依次为熔池闭环控制温度、保温箱预热温度、超声振动频率;激光多层熔覆纳米Al2O3-13%TiO2涂层最佳工艺参数为熔池闭环控制温度2 500℃,超声振动频率50 kHz,保温箱预热温度400℃;优化工艺熔覆的涂层各层之间无明显界面,涂层内部致密、连续,基本无孔隙及贯穿性大裂纹,涂层结合强度明显提高,达66.3 MPa。     

低压铸造-轧制法快速制备Al-Cu复合材料

采用低压铸造-轧制法实现了快速制备650mm×30mm×7mm×R3.5mm的Al/Cu复合材料,并通过SEM、EDS、XRD和电子万能试验机(AG-X)表征其结构和界面剪切强度。结果表明:在Cu管预热温度200℃,轧制压下率30%,冷却水通量400L/h,Al液温度680~740℃条件下均可实现Al-Cu之间的冶金结合,界面合金层随着Al液温度的升高而变宽;复合材料的导电性能和界面结合剪切强度受界面金属间化合物层宽度的影响,其宽度越宽,剪切强度降低。低压铸造法制备Al-Cu复合材料工艺流程短,一次成形快,并能对界面物相进行有效调控。     

Interfacial structure of steel–aluminum bonding plate under non–equilibrium rapid solidification

A steel–aluminum solid–liquid bonding plate is prepared using a non–equilibrium rapid solidification method (including four kinds of processes such as roughening the steel plate surface, immersing influx at the steel plate surface, short–time bonding and rapid solidification). The interfacial structure of the bonding plate is investigated by means of electron probe microanalysis and X–ray diffraction. The results show that the interfacial structure of the bondingplate under non–equilibrium rapid solidiication is quite different from that of the bonding plate in conventional steel–aluminum solid–liquid bonding, i.e. the interface of the bonding plate under non-equilibrium rapid solidification ismade up of an aluminum-rich region (in the form of a group of Fe₄Al₁₃ teeth that grow from the contact surface to the steel side) at the bulge of steel plate surface and an aluminum–poor region (in the form of Fe–Al solid solution of which the Al content is less than 3.5 wt%) at the concave surface of the steel plate alternately.     

Interfacial structure of steel–aluminum bonding plate under non-equilibrium rapid solidification

A steel–aluminum solid–liquid bonding plate is prepared using a non-equilibrium rapid solidification method (including four kinds of processes such as roughening the steel plate surface, immersing in flux at the steel plate surface, short-time bonding and rapid solidification). The interfacial structure of the bonding plate is investigated by means of electron probe microanalysis and X-ray diffraction. The results show that the interfacial structure of the bonding plate under non-equilibrium rapid solidification is quite different from that of the bonding plate in conventional steel–aluminum solid–liquid bonding, i.e. the interface of the bonding plate under non-equilibrium rapid solidification is made up of an aluminum-rich region (in the form of a group of Fe₄Al₁₃ teeth that grow from the contact surface to the steel side) at the bulge of steel plate surface and an aluminum-poor region (in the form of Fe–Al solid solution of which the Al content is less than 3.5 wt%) at the concave surface of the steel plate alternately.     

多层金属复合板的热轧制备方法

提高成材率和复合界面质量是制备多层复合板的难题。本工作提出一种多层复合板的高成材率热轧制备方法,即采用氩弧焊固定各层原料板组成坯料,坯料放入金属套后抽真空,再加热到1000~1200℃进行多道次轧制,成功制备出2.5mm厚的67层复合板。通过金相显微镜及电子显微镜观察和分析了界面组织及元素扩散行为,采用拉伸、剪切实验测定复合板的力学性能,并分析其剪切断口。结果表明:采用两步组坯复合和工艺优化,多层复合板的轧制成材率达90%以上。多层复合板具有良好的结合界面,其抗剪强度达到241MPa。9Cr18和1Cr17镍中间层可以较为有效地阻碍界面附近的碳扩散并改善复合板的组织特征。     

Slurry Preparation and Rolling of Semi-solid 60Si2Mn Spring Steel

The nondendritic semi-solid slurry preparation of 60Si2Mn spring steel has been studied in this paper. The experiments have shown that when stirred for 2 min on the test condition, the semi-solid slurry with 50%～60% fraction solid and spherical primary austenitic grains in the size of 100～300μm can be obtained and is easy to be discharged from the bottom little hole of the stirring chamber. The nondendritic slurry of 60Si2Mn spring steel can be rolled into given plate form successfully, but the solid phase and liquid phase is easy to be separated in rolling process so that the solid primary austenite is concentrated in the center and the liquid is near the edge of the rolled plate. The rupture strength and elongation of the plate rolled only once with semi-solid slurry are lower than that of the traditionally repeated hot-rolled plate of 60Si2Mn spring steel.     

纳米SiO2对钢纤维/混凝土高温后力学性能及微观结构的影响

研究了掺纳米SiO₂的钢纤维混凝土(NSFC)、 钢纤维混凝土(SFRC)和普通混凝土(NC)三种材料在不同加热温度后的抗压、 劈裂和抗折强度等力学性能, 对不同温度热处理后的微观结构进行了SEM分析, 对钢纤维与过渡区界面的相结构进行了XRD分析。结果表明: 在测试温度范围内, NSFC的抗压、 劈裂和抗折强度均高于SFRC和NC的强度, 且在400 ℃时达到最大值。在常温下, NSFC的抗压、 劈裂和抗折强度较NC分别提高27.01%、 63.28%和54.12%, 400 ℃高温热处理后比NC分别高35.09%、 84.62%和87.23%; SEM分析表明, 在钢纤维与过渡区的界面处, 致密度提高, 显微硬度提高。由于固相反应, 使界面区结构发生变化, 在钢纤维表层形成扩散渗透层(白亮层), 即化合物层, 呈锯齿状, XRD分析证明, 白亮层主要由FeSi₂和复杂的水化硅酸钙组成, 从而增强了钢纤维与基体的粘结力, 提高了混凝土的高温力学性能。     

Fe/Al异质金属接头界面组织演变、生长动力学及力学性能

采用真空扩散连接方法研究Fe/Al异质金属接头界面组织演变规律、金属间化合物(intermetallic compound,IMC)生长动力学及力学性能。结果表明：焊接温度为550 ℃时,接头界面无IMC生成,当焊接温度超过575 ℃时,界面由Fe₂Al₅及少量FeAl₃ IMC构成,且随焊接温度升高IMC层迅速长大。在120 min保温时间条件下,接头剪切强度随焊接温度的升高先增加后降低,当焊接温度为575 ℃时,接头剪切强度达到最大值37 MPa。在550~625 ℃范围内,基于热力学分析得出Fe₂Al₅的吉布斯自由能ΔG_Fe-Al最低,而FeAl₃的ΔG_Fe-Al次之,在接头界面处IMC生成顺序为Fe₂Al₅→FeAl₃。Fe/Al接头界面IMC的生长随焊接温度呈抛物线规律,其生长激活能为282.6 kJ·mol^-1。在575,600,625 ℃条件下,界面IMC的生长速率分别为1.13×10^-14,3.59×10^-14,1.21×10^-13 m²·s^-1。