材料内部裂纹自修复中组织生长机制

为探索高温塑性变形过程中裂纹修复规律 ,采用高温物理模拟方法研究了 2 0 Mn Mo材料内部孔隙性裂纹的自修复过程。实验中发现在裂纹修复过程中普遍存在着缺陷自由面上组织生长现象 ,该现象解释了自修复消除孔隙的原因 ,证实了裂纹修复的再结晶机制。研究结果对揭示裂纹演化和修复机理具有重要意义 ,在实际生产中能够作为修复裂纹的指导原则。该成果对于控制塑性加工中缺陷的变化过程具有重要的理论意义和实用价值     

高速钢高温形变动态再结晶机制(英文)

本采用金相、扫描和透射等手段,研究了高速钢高温形变和动态再结晶行为,建立了动态再结晶的微观模型。分析了高温形变时的动态析出过程,并讨论了动态析出与动态再结晶之间的关系。结果表明,高速钢由于形变时基体中存在大量的残余碳化物以及在形变过程中大量的动态析出,其形变再结晶行为远比低碳低合金钢复杂。钢中的动态再结晶方式与析出十分密切。不同的形变条件下变形会发生不同的动态析出,从而引起不同的动态再结晶方式。高速钢中存在两种最基本的动态再结晶方式,即形核长大方式和晶粒碎化方式。     

超临界二氧化碳GAS重结晶制备HMX微细颗粒的研究

比较了ＣＯ２对丙酮，环己酮，二甲基亚砜体积膨胀的影响和ＨＭＸ在上述三种溶剂中ＧＡＳ重结晶时的析晶率。以丙酮为溶剂用ＣＯ２ＧＡＳ重结晶，在一定的条件下可获得２－１３μｇβ－型ＨＭＸ微细颗粒。     

连铸温度范围内钢的蠕变性能

研究了钢在低应变速率下的热塑性,得出了描述应变速率与热塑性关系的模型。研究结果表明,低应变速率下的热塑性与蠕变密切相关。     

掺杂钨丝的再结晶

本文利用金相显微镜、扫描电镜、透射电镜和X射线衍射技术研究了掺杂钨丝的微观组织变化,同时对不同温度下退火处理的样品进行了抗拉强度、显微硬度和室温内耗的测定。结果表明,掺杂钨丝退火时可分为三个阶段:回复、一次再结晶和二次再结晶。文中提出了亚晶聚合是一次再结晶的主要形核机制的观点。     

X70管线钢热轧过程中奥氏体再结晶模型

给出了X70管线钢热轧过程中的再结晶模型 .利用热模拟实验对再结晶率表达式中的常数进行了回归 ,并根据模型对热轧过程中的再结晶进行了计算 ,计算结果与实验结果相吻合     

Dynamic recrystallization of electroformed copper liners of shaped charges in high-strain-rate plastic deformation

The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were investigated by transmission electron microscopy (TEM). Meanwhile, the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis illustrated that unlike the as-formed electroformed copper linersof shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate. Optical microscopy shows a typical recrystallization structure, and TEM examination reveals dislocation cells existed in the thin foil specimen. These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process, and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.     

Effect of dislocation configuration on non-equilibrium boron segregation during cooling

Different densities and configurations of crystal defects were obtained in an austenitic Fe-30%Ni alloy and an ultra low carbon bainitic (ULCB) alloy by undergoing different deformations and annealing treatments at high temperatures. Boron segregation on grain boundaries and subgrain boundaries during air-cooling were revealed by means of the particle tracking autoradiography technique. It is found that non-equilibrium segregation is resisted indeformed grains after recovery and polygonization, boron-depleted zones seem to be quite clear inrecrystallized grains than those in deformed original grains during cooling. Subgrain boundaries andpolygonized dislocation cells have a significant effect on non-equilibrium boron segregation duringthe air-cooling. The results implicates that dislocation configuration is a more important factor affecting boron segregation at grain boundaries rather that the density of defects itself in thegrain.     

Effect of compression direction on the dynamic recrystallization behavior of continuous columnar-grained CuNi10Fe1Mn alloy

The dynamic recrystallization (DRX) behavior of continuous columnar-grained (CCG) CuNi10Fe1Mn alloy was investigated by hot compression along the solidification direction (SD) and perpendicular to the solidification direction (PD). Specimens were compressed to a true strain of 0.8 at temperatures ranging from 25℃ to 900℃ and strain rates ranging from 0.01 to 10 s-1. The results indicate that DRX nucleation at grain boundaries (GBs) and DRX nucleation at slip bands (SBs) are the two main nucleation modes. For SD specimens, C-shaped bending and zig-zagging of the GBs occurred during hot compression, which made DRX nucleation at the GBs easier than that at the SBs. When lnZ ≤ 37.4 (Z is the Zener–Hollomon parameter), DRX can occur in SD specimens with a critical temperature for the DRX onset of ~650℃ and a thermal activated energy (Q) of 313.5 kJ·mol-1. In contrast, in PD specimens, the GBs remained straight, and DRX nucleation occurred preferentially at the SBs. For PD specimens, the critical temperature is about 700℃, Q is 351.7 kJ·mol-1, and the occurrence condition of DRX is lnZ ≤ 40.1. The zig-zagging of GB morphology can significantly reduce the nucleation energy at the GBs; as a result, DRX nucleation occurs more easily in SD specimens than in PD specimens.     

热轧高碳钢线材组织-性能预报系统

在模拟实验和工业试验验证的基础上,建立了高碳钢高速线材在轧制和冷却过程中组织演变及力学性能系列模型,包括临界应变、奥氏体动态及静态再结晶、奥氏体相变体积分数、珠光体片间距以及组织-性能关系等子模型.基于以上模型,开发了一个模拟程序,对高速线材生产的物理冶金过程进行了仿真计算,得到轧件的温度场、奥氏体晶粒尺寸演变、最终组织特征和力学性能.模拟结果显示主要轧制温度及最终组织性能与现场实测结果吻合较好.