34CrMoA转子钢高温循环蠕变断口分形维数与蠕变性能的关系

用垂直剖面法测定了34CrMoA转子钢在550℃循环蠕变断口的分形维数,分析、比较了分形维数与蠕变性能的关系,结果表明,分形维数与断裂应变呈线性关系。     

晶界碳化物对Fe-Cr15-Ni25合金蠕变裂纹扩展行为的影响SCIEI

在两种不同晶界状态下研究了Fe-Cr15-Ni25合金的蠕变裂纹扩展行为。单相合金的空洞在晶界三叉点处形核,而对晶界上有碳化物析出的合金,空洞在晶界碳化物上形核。晶界碳化物阻碍了空洞的长大和连接,因而大大提高了蠕变裂纹扩展抗力。     

小冲孔蠕变试验技术

小冲孔蠕变试验技术是获取在役构件蠕变性能的一种新方法，由于它具有接近无损取样的特点，因此受到学术界和工业界的广泛重视。本文简要回顾了小冲孔蠕变试验技术的发展及应用，重点介绍了典型小冲孔蠕变试验装置的组成及结构，指出了小冲孔蠕变试验技术目前存在的问题和广阔的应用前景。     

Ti-25V-15Cr-2Al-2Mo-0.2C阻燃β钛合金的蠕变变形结构研究

采用TEM技术研究了具有不同热处理组织的Ti-25V-15Cr-2A1-2Mo-0．2C合金存在540℃，250MPa，100h蠕变作用后的变形结构。结果表明：位错环组是合金蠕变变形结构中的典型位错组态；合金的蠕变抗力随β基本上弥散分布的第二相析出数量的增加而提高。添加微量能提高蠕变抗力的合金元素，如Si元素等，是改善合金蠕变性能的可行途径。     

High-temperature corrosion and creep of Ni-Cr-Fe alloys in carburizing and oxidizing environments

The carburization of NiCr 32 20 and NiCrSi 60 16 has been studied in CH₄-H₂ mixtures in the temperature range 900–1100°C. The methods included thermogravimetric measurements and studies on reacted specimens by X-ray diffraction, metallographic, and chemical analysis. Upon carburization internal carbides M₇C₃ and M₂₃C₆ are formed (M=mainly Cr); the rate of carburization is determined by carbon diffusion in the Fe-Ni matrix with carbide precipitations. The effect of the alloying elements Ni and Si on the carburization resistance of austenitic alloys is explained. By the same methods the oxidation and carburization in CO-H₂O-H₂ mixtures have been studied. The important role of a stable chromium oxide layer for the carburization resistance was confirmed. Creep tests at 1000°C in a CO-H₂O-H₂ atmosphere where Cr₂O₃ is stable showed carburization occurring through cracks in the oxide layer. At high strain rates premature failure occurs by carburization, which is followed by internal oxidation and formation of cracks, voids, and holes.     

Creep-induced local lattice parameter changes in a monocrystalline nickel-base superalloy

The γ-γ lattice mismatch of specimens of the monocrystalline nickel-base superalloy SRR 99 has been measured by a high-resolution X-ray diffraction technique for the undeformed state and after high-tem-perature creep deformation. During creep deformation beyond the minimum creep rate (total strain =0.5%), the lattice mismatches, measured in and perpendicular to the [001] stress axis, respectively, un-dergo changes in opposite directions. This reflects the buildup of a complex deformation-induced triaxial state of internal stress in the phases y and γ. The overall resolved shear stresses that act in γ and y due to the combined action of the external and internal stresses are estimated, and the conditions under which cutting of the γ phase by dislocations should occur are discussed.     

二元稀土镁合金Mg-La和Mg-Nd的组织和性能

系统研究了二元稀土镁合金Mg-2%La(L2)和Mg-2%Nd(N2)的铸态显微组织、拉伸性能和抗蠕变性能.通过研究发现,L2铸态组织中有大量网状的Mg-Mg17La2的共晶相析出;而N2则以Mg12Nd离异共晶析出,析出物的数量少得多.N2合金在室温或者175℃条件下,强度和塑性都优于L2合金.N2合金的抗蠕变性能在175℃、70 MPa条件下比L2低近3个数量级.通过计算两种合金的应力指数和蠕变激活能,L2合金的蠕变机制是受晶界滑动控制的,而N2合金为位错攀移机制控制.     

金属间化合物TiAl(W,Si,B)合金的组织稳定性及其蠕变性能

Ti-45Al-2W-0.5Si-0.5B(ABB-23)铸造合金在800和900℃长期时效过程中发生组织失稳，包括α2板条断裂和合并，α2相转变为B2相，针状B2相球化和长大，γ等轴晶的生成以及片层间距的增加。ABB－23合金的热稳定性优于无B的ABB－2合金，表明添加B有利于提高合金的热稳定性。ABB－23合金在700－800℃范围内的抗蠕变能力超过同比密度的抗热腐蚀高温合金IN738LC，具有优异的高温蠕变性能。此外，还对比了ABB－23合金与其他几种TiAl基合金的高温蠕变性能。     

改善操作延长转化炉炉管寿命

分析转化炉炉管不正常原因及对炉管造成的危害，确定通过改善工艺操作来延长转化炉炉管寿命，实践证明效果明显。     

Evaluation of the characteristics of a viscoelastic material from creep analysis using the universal viscoelastic model. I. Isolation of the elastic component designated as the “Projected Elastic Limit”

In a preceding publication this author introduced a new universal viscoelastic model to describe a definitive relationship between constant strain rate, creep, and stress relaxation analysis for viscoelastic polymeric compounds. One extremely important characteristic of this new model is that it also characterizes secondary creep very well. Because secondary creep is the linear portion of creep after the completion of primary creep, then a straight line with a slope and an intercept can describe secondary creep. To effectively define a straight line in the secondary creep region it was found necessary to obtain averages of the instantaneous slope and the instantaneous intercept strain by averaging over a series of equally spaced data points in the secondary slope region. Most importantly, this average intercept strain was found to be independent of creep stress and creep time. This means that all the secondary creep straight lines must pass through the same intercept creep strain for all creep stresses. The results presented in this study strongly indicate that this secondary creep intercept strain is independent of creep stress and creep time, and appears to increase as the value of the efficiency of yield energy dissipation decreases. Because a decrease in the efficiency of yield energy dissipation, n, appears to correlate with an increase in the elastic solid like character of a material, then it appears that this secondary creep intercept strain should be a direct measure of the strain that the material can survive to retain its full elastic character. Therefore, this secondary creep intercept strain has been designated as the “Projected Elastic Limit” of a given viscoelastic material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2923–2936, 2003