碳对镍基单晶高温合金AM3凝固组织的影响

研究了碳(C)对第一代镍基单晶高温合金AM3显微组织的影响。结果表明,随着碳含量的增加,枝晶形貌和间距无明显变化,合金中共晶的数量明显减少,一次碳化物逐渐增多。该合金中一次碳化物形貌通常为块状、骨架状和汉字状。当含碳量较高时,碳化物形貌为由骨架状连接形成的网状碳化物(汉字状碳化物)。     

球墨铸铁中白口共晶形成的数值模拟

建立了球铁稳定系和介稳定系共晶转变的数学模型。同时考虑了元素微观偏析和不同组织所产生潜热的影响。对球铁试样进行了定量金相实验分析，并与模拟结果进行了比较，结果表明，石墨球数量和尺寸以及碳化物体积分数的模拟结果与实验结果吻合，对白口共晶生长，碳化物形貌与凝固方式的关系进行了分析和讨论，表明凝固分析和模拟可以在一定程度上预测球铁中白口共晶的生长及最终碳化物的形貌。     

BEHAVIOUR OF Ti IN AS-CAST MEDIUM MANGANESE AUSTENITIC STEEL

The majority of Ti is found to be preferentially precipitated in the form of TiC from mediummanganese steel melt.The TiC may contribute to the heterogeneous nuclei of fine austenitecrystallization,to the retardation of dislocation movement as well as to pile-up andproliferate the dislocations,thus,the matrix of the as-cast steel will be effectively strength-ened.It was also found that the TiC can be acted as the heterogeneous nuclei of the nodulareutectic carbide formation and caused the dispersion o fan abundance of the carbide in theinterstices between austenite dendrite arms.     

合金元素对高碳高速钢中碳化物形成及形态的影响

采用铸造方法制备了高碳、高钒和变质处理为特征的亚共晶（５％Ｖ）和过共晶（８％）     

球墨铸铁缩松分析计算模型的建立

用系列试验铸件研究了主要工艺因素(碳当量、孕育量以及铸件模数)对球墨铸铁件缩松产生的影响规律。结果表明,在试验选择的范围内,随着碳当量增大、孕育量增加,缩松面积率减小;对亚共晶和共晶成分的球铁,模数的减小会导致缩松面积率的增大;对过共晶球铁,缩松面积率随模数增大而减小。通过对试验数据的回归分析,建立了球墨铸铁缩松面积率计算模型。为球墨铸铁缩松的预测模拟计算提供了依据。     

超高碳球墨耐磨铸钢组织研究

研究了一类新型耐磨耐热材料—球墨铸钢。通过研究发明的新型球化剂,对超高碳钢钢液球化处理,铸态组织中除珠光体外,还含有一定数量的球状石墨和碳化物。重点分析了球墨铸钢铸态、退火、正火、锻造后的组织特征。研究表明:球墨铸钢经热处理后球化效果提高、基体组织细化,尤其正火、锻造后可获得大量的球状碳化物,与传统的高碳钢碳化物球化工艺有显著的差异。     

碳对镍基单晶高温合金碳化物形貌的影响(英文)

在抽拉速率为50μm/s的条件下制备5种不同含碳量的单晶高温合金,研究碳对单晶高温合金中碳化物形貌的影响。研究发现,铸态组织中存在4种形貌的MC型碳化物,呈针状、球状、块状以及中文汉字状。随着碳含量的增加,碳化物的体积分数增大而共晶组织的体积显著减少。同时,碳化物的尺寸随着碳含量的增加亦呈增大趋势。     

Microstructural evolution of fine-grained ZA27 alloy during partial remelting

The microstructural evolution process of fined-grained ZA27 alloy during partial remelting has been investigated.The relationship between the as-cast and semi-solid microstructures has been discussed in particular.The results indicate that a semi-solid microstructure with small and spheroidal primary particles can be obtained when the Z.A27 alloy is partially remelted.The microstructural evolution can be divided into four stages,the initial coarsening of the dendrites due to coalescence of dendrite arms,structural separation resulted from the melting of residual interdendritic eutectic,spheroidization due to the partial melting of solid particles and final coarsening attributed to the coalescence and Ostwald ripening.An equiaxed dendrite in the as-cast microstructure may evolve into one spheroidal particle in the semi-solid microsturucture after being partially remelted.The more equiaxed the dendrites in an as-cast microstructure are,the more spheroidal the solid particles in the semi-solid microstructure will be.Finer primary particles could be obtained if the alloy with finer as-cast microstructure was partially remelted.However,due to the coalescence effect,their sizes cannot be reduced further if the refined as-cast microstructure reached a certain extent.     

Fe-Ni-P-B共晶合金的深过冷凝固组织演化

采用玻璃熔覆法使Fe-Ni-P-B共晶合金在不同过冷度条件下凝固,研究了其组织随过冷度的演化规律.结果表明,随着过冷度的增加,凝固组织形态逐渐从棒状规则共晶向不规则的粒状共晶组织转化.当T＜35 K时,棒状规则共晶组织随过冷度增加而逐渐细化;当35 K＜ T＜150 K时,凝固组织由团状非规则共晶与棒状规则共晶构成,且随着过冷度增加非规则共晶逐渐增多,规则共晶组织减少,共晶间距增大;当T＞150K时,获得完全非规则共晶组织.应用Jackson-Hunt共晶生长模型和枝晶熔断理论,对Fe-Ni-P-B共晶合金凝固组织形成机制进行了分析讨论.     

Influence of fabricating process on microstructure and properties of spheroidal cast tungsten carbide powder

A super-high temperature furnace was developed to fabricate spheroidal cast tungsten carbide powder with excellent flowability and fine feathery structure in a large scale. Optical microscope and scanning electron microscope were taken to characterize the morphology and microstructure of cast tungsten carbide powder. X-ray diffractometry was used to analyze the phase composition of powders involved. It is found that the carbon potential in the furnace and feeding speed play an important role on the microstructure, morphology and properties of the spheroidal cast tungsten carbide powder. As carbon potential is between 0.3% and 0. 9% in the furnace, cast tungsten carbide powder with hardness over 2800( HV0.5), flowability over 7.1 s/50 g and tap density over 10.3 g/cm^3 is obtained.     

化学成分对铁-铬-碳系堆焊材料抗磨蚀性能的影响

为解决水轮机在含沙水中的快速破坏,对铁-铬-碳系堆焊材料进行了研究,并在自行设计、制造的沙水旋流磨蚀试验机上进行了评定堆焊材料的抗磨蚀性能试验。试验结果表明,材料的抗磨蚀性能主要决定于初生析出相碳化铬的含量。随着碳、铬含量的降低,初生析出相由硬度高于共晶的碳化铬变为硬度低于共晶的合金固溶体,从而降低了堆焊层的硬度与抗磨蚀性能。含碳量进一步降低,堆焊层组织中的共晶将减少,固溶体相将相应增加,这样堆焊层的硬度与抗磨蚀性就会进一步降低。硼能提高高碳高铬白口铁焊条堆焊层的抗磨蚀性。硼对13%铬钢焊条堆焊层的抗磨蚀性的影响比对高碳高铬白口铁焊条更加明显。随着含硼量的增加,13%铬钢焊条堆焊层的硬度与抗磨蚀性基本成直线增长。     

W6钢电子束焊后表面重熔硬化

高速钢是一种具有高硬度、高耐磨性的特殊工具钢.对于进行过球化退火的高速钢,其显微硬度损失较大,严重影响其应用.为恢复球化退火W6Mo5Cr4V2高速钢表面的显微硬度,同时保证其内部良好的韧性不受影响,采用电子束表面重熔对其表面进行硬化.结果表明,重熔表面整体呈现平整光滑状态,存在小尺寸熔坑,重熔层内部呈现胞状树枝晶组织,主要由马氏体、残余奥氏体、晶间网状M₂C共晶碳化物以及细棒状MC碳化物组成,呈现不均匀的条带状分布,在重熔区边界存在未熔碳化物,在重熔区中心区域碳化物均匀性较高,并对晶间碳化物的形成机理进行了分析.经过电子束表面重熔,由于晶内针状马氏体以及晶界脆性碳化物生成,W6Mo5Cr4V2高速钢表面的显微硬度由283 HV提高到800 HV以上,母材的显微硬度恢复效果显著.     

Structural evolution of non-dendritic AlSi7Mg alloy during reheating

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Effect of solidification parameters on the microstructures of a single crystal Ni-based superalloy AM3

A single crystal Ni-based superalloy AM3 was processed at withdraw rates of 3.5, 10, 50, 100, 200, and 500 μm·s-1, respectively.The as-cast microstructures and solidification segregation ratio were characterized with various withdraw rates.The shape and size of carbide microstructures were determined.As expected, the primary and secondary dendrite arm spacings (PDAS and SDAS) decrease with the increase of withdraw rate.The highest volume fraction of eutectic γ/γ' is observed at the 100 μm·s-1 withdraw rate.The volume fraction of eutectic γ/γ' does not appear to be a strong function of the withdraw rate.With increasing withdraw rate, interface morphologies change in the sequence of planar, cellular, and dendrite.There is a general refinement of the microstructure as the withdraw rate increases.EPMA analysis showed that withdraw rate does not have obvious influence on the segregation of elements.     

TiAl合金激光表面合金层中TiC凝固生长形态及机制

利用碳对TiAl金属间化合物合金进行激光表面合金化 ,制得了以TiC (MC碳化物 )为增强相的复合材料涂层 ,研究了MC碳化物的凝固生长形态及生长机制。结果表明 :在激光扫描速度为 6 .0mm/s的凝固条件下 ,MC碳化物呈现微观上具有“小片链状”生长特征的树枝状生长形态 ;当激光扫描速度增加至 16 .4mm/s时 ,其生长形态又转化为具有“三维网络”生长特征的发达树枝晶 ;TiC与Al3 Ti共晶的动力学生长过程及MC碳化物所固有的侧向生长机制是影响MC碳化物凝固生长形态选择的重要因素     

Ni基合金激光熔覆层组织特征及凝固过程的研究

采用自动送粉方法,在４５钢表面激光熔覆Ｎｉ基合金粉末,较为系统地研究了扫描速度对激光熔覆层显微组织特征的影响。实验结果表明：Ｎｉ基合金粉末激光熔覆层显微组织由枝晶及块状（或针状）共晶组织构成,共晶碳化物的形态由化学成分确定;结合界面不存在白亮带,为细小亚共晶组织;离结合界面距离的增加,熔覆层组织逐渐变细,显微组织表现出明显不均匀性,提高激光扫描速度,明显细化了组织邮组织显微硬度。改善了熔覆层局部组     

激光功率对激光熔覆WCP/Ni基金属陶瓷涂层的组织与磨损性能的影响

研究了3种不同功率(1．8kW、2．2kW、2．6kW)对激光熔覆WCp／Ni基金属陶瓷涂层的组织与磨损性能的影响．选择合适的激光功率(2．2kW)，可以获得WCp均匀分布并与基体合金结合良好的WCp／Ni涂层．激光熔覆过程中WC颗粒与基体合金界面间发生了扩散反应溶解，导致未熔WC颗粒周围形成了块状的富W碳化物，功率较高时更加明显．激光熔覆WCp／Ni基涂层由未熔WC颗粒，块状或枝晶状的富W碳化物，杆状的富Cr碳化物以及其间的γ枝晶固溶体及其共晶组织所组成．不同激光功率下的WCp／Ni涂层的显微硬度与耐磨性均远高于Ni60涂层，其中2．2kW功率的WCp／Ni基涂层的显微硬度最高，耐磨性最好。     

流变铸造半固态亚共晶高铬铸铁组织形成研究

研究了亚共晶高铬铸铁半固态球状晶的形成条件及规律。结果表明：通过控制合适的浇注温度，并对充型前的金属液进行激冷处理，同时对过冷的金属液配以适当的振动，可以获得球形或近球形的先共晶奥氏体非枝品组织；在带有倾斜板冷却体的低温浇注情况下，金属液的冲刷、流动及振动使熔体获得了均匀的溶质场和温度场，抑制了发达的先共晶奥氏体枝晶的形成，为球状晶的获得提供了条件。     

Structure and ductility of eutectic type iron-carbon alloys

Conclusion The ductility of iron-carbon alloys of the eutectic type is governed by the structure of eutectic carbides and it may be increased by two methods. The first envisages formation during prior heat treatment of dislocations in eutectic carbides and creation of subgrain boundaries along which during deformation there is carbide fragmentation. This method, as a result of the specific effect of the metal base on formation of dislocations in carbides and prevention of carbide failure under the action of compressive stresses from the surrounding solid solution, may only be used for alloys in which the carbide phase reinforces a metal matrix. The second method involves a marked increase in carbide ductility as a result of transformation occurring in them under the action of deformation [10]. This method may be used to increase the ductility of cast irons around the eutectic composition with eutectics whose matrix phase is carbide. In this way forming may be accomplished by rolling in the range of rates used in metallurgical production practice.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 5–9, September, 1984.