钽钨合金轧制变形过程中不同剪切带组织的形成机理及其演变规律

The shear bands have an important effect on the microstructures and properties of metal materials. However, the microstructure characteristics and formation mechanism of the shear bands in BCC metals are not clear. A series of different kind of shear bands with different scales and morphology are formed in Ta-W alloy during plastic deformation process. This project will study the mechanisms of formation of these shear bands and their evolution during the rolling process systematically. The main research is to reveal the formation mechanism of shear bands by investigating the morphology of shear bands in different reduction, characteristics of dislocation substructure, dislocation boundaries and dislocations contents in these shear band, which will show the crystallographic characteristics, macroscopic orientation relationship between samples. The interaction between shear bands and microbands, grain boundary will be studied carefully, which will show the evolution of these shear bands during rolling. The relationship among the formation of shear bands, grain orientation and rolled-reduction will be studied. The evolution of shear bands and their effects on the microstrcture, texture and mechanical properties will be developed. The structure and mechanical properties of Ta-W alloy can be controlled through this study, which provides important experimental data and theoretical basis. In addition, a theoretical reference for the plastic processing of other BCC metals can be obtained.

金属材料在塑性加工过程中形成的剪切带对材料的组织和性能产生重要影响。而关于体心立方结构金属中剪切带的结构特征及其形成机理还不是很清楚。本项目拟系统深入研究钽钨合金轧制变形过程中不同尺度和形态的剪切带的形成机理及其演变规律。通过研究钽钨合金在不同应变量下剪切带组织的宏观形貌以及剪切带区域内的位错亚结构、位错界面及其组成特点，明确剪切带相对样品坐标系的宏观取向特征及微观的晶体学特征，揭示剪切带的形成机制；研究剪切带与微带和晶界的相互作用机制，探明剪切带的演变规律；研究剪切带区域新生晶粒与基体之间的关系，探讨剪切带演变过程中晶粒细化和取向转变的微观机理，阐明剪切带对钽钨合金的组织结构、织构和力学性能的影响。本研究不仅可为钽钨合金的组织和力学性能控制提供重要的技术基础和理论依据，还可为其他体心立方金属的塑性加工和成形给予理论参考。

金属材料在塑性加工过程中形成的剪切带对材料的组织和性能产生重要影响，而体心立方结构金属中剪切带的结构特征及其形成机理还不是很清楚。本项目旨在系统深入研究钽钨合金轧制变形过程中不同剪切带的形成机理及其演变规律。本项目制备了Ta-2.5W和Ta-10W两种成分的合金板材，并分别对两者进行了5%-90%的冷轧变形。观察了不同变形状态试样的显微组织，测试了材料硬度及宏观织构，在此基础上研究了钽钨合金中晶粒取向与晶内剪切带组织之间对应关系。后阶段，进一步对材料的宏观织构进行了分析，对比了两种不同钨含量织构组分特点以及材料芯部与表面的织构分布特点。利用EBSD观察了材料中的剪切带组织特点。利用TEM观察了不同钨含量材料中的位错组态。分析了钨含量对织构的影响，以及钨含量对变形组织的影响。分析了大变形过程中新晶粒的形成机制。本项目经过大量的微观组织测试表征和晶体学分析工作，深入系统地研究了剪切带在钽钨合金塑性变形过程中的形成、演变及对新晶粒产生的影响，从而可以解释剪切带对材料的织构及性能的影响。这对钽钨合金乃至体心立方难熔金属的塑性加工生产有重要的理论指导作用，并且能够为解决一些实际生产问题提供思路。