镍基单晶高温合金的微孔加工对比实验研究

开展镍基单晶高温合金微孔加工实验研究,探讨不同直径、不同截面形状的电极对微孔的尺寸精度、表面质量、加工效率和亚表面损伤等方面的影响.研究结果表明,微细螺旋电极的加工效率远大于圆柱电极,其中直径200μm的微细螺旋电极的微孔加工效率比相同直径下的圆柱电极提高17%,而直径300μm的微细螺旋电极的加工效率可提高30.56%;微细螺旋电极加工的微孔扩孔量小于圆柱电极的扩孔量,且微细螺旋电极加工得到的孔壁质量优于圆柱电极的;微细螺旋电极所加工的微孔的亚表面损伤层连续且厚度小于圆柱电极所加工的微孔.     

师昌绪在高温合金领域的重大贡献

 师昌绪是当代著名的金属学及材料学科学家。在高温合金领域,最先提出并攻克了包套挤压工艺难关,为变形高温合金的生产开辟了一条新的途径;铸造高温合金方面,研究出中国第一代空心气冷铸造镍基高温合金涡轮叶片,使中国成为世界上第二个采用这种叶片的国家;发现了凝固偏析的新规律,总结了"低偏析合金技术",推动了高温合金的发展,被美国同行尊称为"中国高温合金之父"。     

K18C镍基高温合金光谱标准样品的研制

采用二次冶炼的方法炼制出K18C镍基高温合金光谱标准样品,其中包含C,Cr,Fe等16种元素。对标准样品的均匀性与稳定性进行了考察。结果表明所研制的K18C镍基高温合金标准样品成分均匀,稳定性优良,5年内各成分量值无变化。委托多家实验室进行协作定值,选择了合适的统计学方法对各协作单位的数据进行检验和计算,获得标准样品的标准值及其扩展不确定度。     

陶瓷刀具高速车削GH4169高温合金切屑实验

针对陶瓷刀具WG300车削高温合金GH4169,设计了车削加工实验,利用扫描电镜（SEM）图和能谱分析（EDS）图对产生的切屑的形态和元素进行研究,得到了切削速度对切屑的影响规律,观察到刀具和工件在切削过程中发生元素的扩散现象.随着切削速度的增加,切屑出现显著的锯齿状,其成分中C的质量分数增多,Al和O元素没有显著变化,表明刀具中的Al2O3较为稳定.该研究对陶瓷刀具加工过程中的切削速度的选择具有指导和参考意义.     

On the precipitation of delta phase in ALLVAC® 718Plus

ALLVAC 718Plus is a new commercial superalloy derived from Inconel 718, but possessing a higher temperature capability whilst employing the same philosophy regarding the microstructure. Many articles have been published describing various heat treatments exploiting the precipitation of intermetallic phases at grain boundaries to optimize the mechanical properties over a range of testing conditions. The requirement to further improve the mechanical properties of this alloy drives our interest in the precipitation mechanism of the delta and eta phases found in this alloy. We report the presence of finely layered structures composed of two phases, delta and eta, with distinct structures and chemistries. Possible pathways to explain this precipitation in 718Plus are considered as follows: (i) the sequential formation of the delta from eta phase and (ii) the simultaneous precipitation of both eta and delta facilitated via solute rejection. Both can result in the formation of those small delta layers observed in HRSTEM. We discuss which is most likely by comparing the relative alignment of the phases by image processing and the analysis of the HRSTEM images, and propose formation mechanisms consistent with the distinctive dislocation structures observed at the interface.     

弯曲晶界对GH49合金蠕变过程中位错组态的影响

本文用电子金相观察了GH49合金两种不同的晶界状态,试样在蠕变断裂过程中位错组态的变化,并研究了位错与晶内γ′相及晶界碳化物沉淀间的相互作用。研究表明:平直晶界试样,晶内蠕变主要是位错攀移越过γ′相所引起,晶界运动受控于晶界滑动。而弯曲晶界试样,晶内蠕变是位错攀移越过r′相及位错切割γ′相所引起,晶界运动受控于晶界滑动与弯曲段内的“回复”移动。因而,弯曲晶界提高了晶内蠕变速率而降低了晶界滑动速率。这就有效地阻止了裂纹的连接、扩展,大幅度地提高了蠕变第三阶段的断裂抗力,从而延长了蠕变寿命及蠕变断裂塑性。     

Pore defects in a nickel-based superalloy with high Ti content

Pores are uncommon defects in superalloy bars, which deserve to be investigated. In this work, a type of pore defect within GH4710 nickel-based superalloy was investigated by 3D X-ray imaging method combined with metallographic analysis. 3D X-ray imaging was used for locating and visualizing the defects in the alloy. The 3D X-ray imaging result of the defects showed a good agreement with the defect anatomical morphologies. It was observed that the pore defect was accompanied by MC carbides, micro-crack, and non-metallic inclusions. The origin of pore defect was attributed to the shrinkage pores, inclusion and the complex precipitates. The analysis showed that the pore defects in GH4710 alloy was associated with strong micro-segregation and complex phase precipitation during solidification, induced by the high weight content of Ti and C in the alloy.     

镍基单晶高温合金表面再结晶控制技术的研究进展

针对镍基单晶高温合金构件的表面再结晶控制技术,结合国内外相关工作的研究状况,从单晶高温合金构件表面再结晶的形成机理、再结晶的表面效应、基于再结晶预防的构件设计、单晶构件热成型过程和冷加工过程再结晶控制技术等几方面,对镍基单晶高温合金构件的表面再结晶控制技术领域取得的研究成果进行总结和分析。重点论述了各国单晶再结晶控制技术,提出中国镍基单晶高温合金构件的表面再结晶控制技术存在的差距及未来研究重点。     

镍基单晶高温合金磨削变质层工艺试验研究

为探究镍基单晶高温合金的磨削变质层工艺特性,采用单因素试验的方法,研究不同磨削参数及冷却条件对磨削变质层厚度的影响规律.结果表明,在镍基单晶高温合金DD5的磨削表面及亚表面存在一定厚度的磨削变质层.磨削变质层中的塑性变形层内γ相和γ′相发生剧烈扭曲变形且磨削变质层的硬度大于基体.不同磨削参数及冷却条件对磨削变质层厚度产生不同影响,随着砂轮线速度、磨削深度、工件进给速度的增加,磨削变质层厚度的变化分别表现为先减小后增大、不断增大、先增大后减小;在试验参数范围内,微量润滑(MQL)作为冷却条件可以降低相应的磨削变质层厚度,最多达到3.5μm.