磷的非平衡晶界偏聚恒温动力学实验及计算研究

选用12Cr1MoV工业用钢,通过俄歇电子能谱分析方法(AES),对磷在1050℃固溶处理温度下,540℃恒温时效过程中的非平衡晶界偏聚浓度进行了测试,在国际上首次获得了磷在钢中的非平衡晶界偏聚动力学完整曲线,该曲线直接验证了由徐庭栋提出的非平衡晶界偏聚动力学理论模型.论文还进行了非平衡晶界偏聚动力学计算,求出了12Cr1MoV钢在540℃恒温过程中复合体的扩散系数Dc及磷原子的自扩散系数Di,并应用非平衡晶界偏聚动力学方程进行了动力学曲线模拟,拟合曲线与实验曲线符合完好.证实了非平衡晶界偏聚的空位-溶质原子复合体扩散机制.     

12Cr1MoV钢的可逆回火脆性非平衡晶界偏聚机制研究

根据实验获得的磷在12Cr1MoV钢中的非平衡晶界偏聚恒温动力学曲线,进行了12Cr1MoV钢的可逆回火脆性动力学研究.在P的偏聚过程、临界时间、反偏聚过程分别选取试样,对试样进行了系列示波冲击试验,测得了不同时效时间试样的DBTT值.实验发现该钢存在过时效现象,即钢材的脆性在开始时随时效时间的延长而逐渐增加,然后又逐渐下降。对材料的可逆回火脆性非平衡晶界偏聚(NGS)机理进行了分析,建立了12CrlMoV钢的可逆回火脆性NGS机制,并依此给出了一种预报和控制钢材晶界脆性的方法.     

低拉应力下12Cr1MoV钢中P原子的晶界非平衡偏聚

对低应力作用下12Cr1MoV钢中磷原子的晶界偏聚现象进行了俄歇能谱实验研究和动力学分析．实验获得了在30MPa拉应力作用下，磷原子在晶界处发生的非平衡晶界偏聚，临界时间是1h．分析表明，低拉应力极大地提高了磷-空位复合体在钢中的扩散速率，低拉应力引起的晶界变形对磷-空位复合体具有强烈的吸引作用．通过动力学计算给出了磷-空位复合体偏聚阶段扩散系数Dc和磷原子反偏聚扩散系数Di随时间变化的表达式．     

非平衡晶界偏聚的临界时间问题研究

以近期建立起来的非平衡晶界偏聚模型为基础，介绍了非平衡晶界偏聚动力学理论。该理论引入了临界时间概念，将等温过程中溶质原子的非平衡晶界偏聚动力学过程分为偏聚过程与反偏聚过程。对等温过程中的临界时间公式进行了理论分析与实验验证，证实了临界时间公式用于预测溶质原子非平衡晶界偏聚量达到极大值的恒温时间的准确性。并且研究了等温过程中的临界时间与连续冷却过程中的有效时间之间的区别和联系，将连续冷却过程等效为恒温过程，利用恒温动力学方程计算连续冷却过程中溶质原子的偏聚量。     

铈、磷晶界偏聚及其相互影响

本文通过改变10Mn2V钢中的铈、磷含量,研究了奥氏体状态下铈、磷在晶界的偏聚规律。研究发现:磷在奥氏体中的偏聚是一种平衡偏聚,随加热温度的升高,晶界的偏聚量下降,其偏聚自由能为-40～-44.5 kJ/mol;铈在奥氏体状态下也向晶界偏聚,但偏聚量随加热温度的升高而增加;当钢中铈、磷共存时,磷在晶界的偏聚量下降,而铈在晶界的偏聚量上升;钢中的铈、磷原子之间有较强的相互作用。     

Cr17Ni2钢高温回火脆性的研究

本文运用扫描电镜、俄歇能谱仪、透射电镜等,研究了Cr17Ni2铜高温回火脆性的产生原因。试验结果表明,这种铜在550℃左右回火时所产生的脆性属于可逆回火脆性,并呈沿晶断裂。俄歇能谱仪分析结果发现,回火脆的Cr17Ni2钢中,磷、铬、镍在奥氏体晶界上偏聚显著。透镜薄膜观察结果发现晶界和位错上有小质点析出。上述现象是高温回火脆性的产生原因。     

硼向奥氏晶界的扩散机制

通过解变温扩散方程,导出了硼在非平衡晶界偏聚的理论公式,建立了晶界贫硼区宽度与淬火加热温度、冷却速度以及非平衡晶界偏聚扩散激活能与扩散常数之间的关系,理论预言与实验结果能较好地吻合.     

硼向晶界扩散机理的研究

通过解变温扩散方程,导出非平衡晶界偏聚的数学表达式,建立了晶界贫硼局域尺寸与淬火加热温度、冷却速度以及非平衡晶界偏聚扩散激活能与扩散系数之间的关系,所得结果与实验结果相一致.     

高强马氏体钢长期时效过程中的微偏聚现象

１４％Ｃｒ－５％Ｎｉ（质量分数）马氏体钢热处理后在４００℃长期时效，强度增加，韧性降低，合金脆化，经分析表明，合金脆化与有害元素Ｐ和合金元素Ｃｒ，Ｎｉ等在原始奥氏体晶界上的微偏聚过程有关。     

奥氏体晶界的硼偏聚对合金钢淬透性的影响

讨论了加硼合金钢在奥氏体化过程中,硼向奥氏体晶界扩散而造成的晶界硼偏聚,它阻止了新相形核,该理论能很好地解释微量硼提高合金钢淬透性的机理.     

沥青路面施工中的离析与防治措施

离析现象是沥青路面施工过程中经常出现的问题,严重的离析会导致沥青混合料的各种力学性能和使用性能的下降,严重影响路面的施工质量,并造成路面的破坏,缩短路面的寿命。对沥青混凝土路面施工中的级配离析、温度离析和碾压离析现象的原因进行分析和讨论,并提出了相应的改进工艺措施和防治技术。     

枝晶偏析的均匀化

本文提出了枝晶偏析的物理图象,并运用菲克第二定律导出了枝晶偏析的溶质分布方程,在此基础上,着重讨论了均匀化退火的时间,并从物理冶金学角度提出了消除枝晶偏析的途径。     

Distribution and segregation of dissolved elements in pipeline slab

The chemical composition in a cross section of a high grade pipeline slab was measured point by point （in a scale of 1 μm） using original position statistic distribution analysis （OPA）. The result indicated that negative segregation strips of Si, Mn, Mo, Ni, Cr, Nb, Cu, Ti, and V exist in the two sides 24 mm away from the central line, with a width of 8-12 mm, Negative segregation inside the central line is more severe than that outside the central line, and the highest positive segregation of the elements appears closely by the inner sides of the negative segregation strips. No obvious negative segregation strip of S and P is found. Segregation of the elements in the central area is higher than that in the outer and inner arc areas. The segregation of C, Ti, S, and P is high and that of Cr, Cu, Si, and Mn is low in the slab.     

沥青混合料离析与空隙率的相关性分析

以SUP16型沥青混合料为例,对现场施工中不同离析状况的沥青混合料进行了性能分析和试验研究,分析了沥青混合料集料离析和温度离析与空隙率的变化关系,以及空隙率对沥青路面压实度和平整度的影响.结果表明:粗集料集中混合料的空隙率平均值为9.5,吸水率高达2.0,粗集料离析对沥青混合料性能的影响更严重;空隙率的变化受沥青混合料温度的影响很明显.随着温度降低幅度增加.空隙率与设计值的偏离增大.路面的压实质量和平整度变差.     

Theoretical progress in non-equilibrium grain-boundary segregation (I): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement

The research progress of non-equilibrium grain-boundary segregation theories in the last 20 years is reviewed. Based on studies by the present authors, the critical time of non-equilibrium segregation and its impact on the development of non-equilibrium segregation theories are described. Quasi-thermo-dynamics and kinetics for thermal non-equilibrium grain boundary segregation are detailed along with a non-equilibrium grain boundary cosegregation model. The experimental validation of the theories and their application to the reversible temper embrittlement of steels and the intermediate temperature brittleness in metals and alloys are also addressed. Supported by the National Natural Science Foundation of China (Grant No. 50771036)     

Effect of boron on hot strips of low carbon steel produced by compact strip production

The effect of boron on hot strips of low carbon steel produced by compact strip production (CSP) to reduce the strength to a certain degree was investigated, which is quite different from that of high-strength low alloy steel. The mechanical properties and microstructural evolution of the hot strip were studied using optical microscopy and tensile tests. By means of an electrolytic dissolution technique and Thermo-Cal calculation, the precipitates containing boron were analyzed and detected. From the electron back-scattered diffraction analysis, it can be deciphered whether the microstructure has recrystallized or not. Furthermore, the effect of boron segregation on the recrystallization or non-recrystallization conditions can be distinguished. The segregation behavior of boron was investigated in boron-containing steel. The nonequilibrium segregation of boron during processing was discussed on the basis of the forming complexes with vacancies that migrate to the boundaries prior to annihilation, which was confirmed by the sub-sequent cold rolling with annealing experiments.     

建筑业性别隔离的成因及治理策略研究

建筑业严重的性别隔离情况使得女性在数量和职位上都难以突破。从生物主义、女性主义、人力资本理论等角度分析产生这种性别隔离的原因,并在此基础上探讨改善性别隔离的意义以及具体的措施。     

Theoretical progress in non-equilibrium grain-boundary segregation (Ⅰ): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement

The research progress of non-equilibrium grain-boundary segregation theories in the last 20 years is reviewed. Based on studies by the present authors, the critical time of non-equilibrium segregation and its impact on the development of non-equilibrium segregation theories are described. Quasi- thermo- dynamics and kinetics for thermal non-equilibrium grain boundary segregation are detailed along with a non-equilibrium grain boundary cosegregation model. The experimental validation of the theories and thei...     

Radiation Induced Segregation of Fe-Cr-Mn(W,V) Alloyunder Electron/Helium Dual-beam Irradiation

The radiation induced segregation (RIS) was studied by electron/helium dual-beam irradiation. Within agrain, the content of Cr and Mn were higher in the center than at the margin of the irradiated areas. In thecontrary, withim the irradiated areas included grain boundaries the contents of Cr and Mn decreased at the grainboundaries. RIS was weaker under dual-beam irradiation than that under electron single-beam irradiation, whichwas because of the increases of dislocation density and sink strength of voids when helium existed.     

预混合饲料用载体的研究与选择

本文利用混合试验及分级试验研究了玉米粉、脱脂米糠、玉米淀粉下脚、提取过肌醇的米糠及混合载体的特性.结果表明,脱脂米糠、提取过肌醇的米糠及米糠与稻壳的复合物的混合性能较好,振动分级和下落分级后的变异系数较小,是预混合饲料良好载体;而玉米粉等振动分级及下落分级均较严重,不宜作预混合饲料的载体.