滑移引起晶粒间的反应应力与典型金属冷轧织构形成理论的研究

New theory for polycrystal deformation, theory of texture formation and corresponding simulation models are proposed, in order to overcome many shortages in current rolling deformation theory for metal polycrystals under modified Taylor principles. The new theory, based on the consideration of intergranular reaction stresses induced during plastic deformation and therefore clearer physic background, will cover variation of real rolling stress tensors, influence of statistic matrix aggregate on the deformation grains, as well as objective calculation of stress and strain tensors of differently oriented grains during rolling, while the calculations become more forthright and strict. Dislocation slips are chosen as crystallographic deformation mechanisms in the models. Pure aluminum, pure iron and α titanium are chosen as typical experimental metals. The cold rolling texture formation will be observed and simulated under different rolling conditions including external stresses, initial textures, strains, matrix texture evolutions, work hardening rates, effectiveness of reaction stresses etc. The influence of grain orientations in deformation matrix on nucleation behaviors and recrystallization texture formation during following annealing will also be investigated. The research will modify current plastic deformation and texture formation theories, improve the physical metallurgical principles of polycrystalline deformation, and offer a new research basis for plastic deformation theory concerning more complicated crystallographic deformation mechanisms.

针对当前以改进Taylor原理为基础的金属多晶体轧制变形理论中存在的多种缺陷，以分析塑性变形时多晶体晶粒间产生的反应应力为背景，研究建立一种基于真实轧制应力状态、统计性地考虑基体对变形晶粒影响、可客观计算不同取向晶粒应力应变状态、物理背景清晰、计算便捷、更加科学而合理的多晶体变形及轧制织构形成理论。基于这种考虑，以滑移系为塑性变形的晶体学机制，选择纯铝、纯铁、α钛合金等为典型金属材料，在适当的轧制变形工艺条件下实验观察并模拟计算不同外加应力、初始织构、变形量、基体织构环境、加工硬化率、基体反应应力作用效率等条件下的轧制织构形成过程，及轧制时晶粒取向演变过程对后续再结晶形核行为和再结晶织构的影响。研究工作将改进现有的多晶体塑性变形理论和织构形成理论，完善金属多晶体塑性变形的金属学原理，并为多晶体以其它复杂晶体学机制塑性变形理论的研究奠定新的基础。

当前大多数各种塑性变形晶体学理论均以泰勒原理为出发点；但这一原理中人为的应变假设导致了科学上一定的疏漏，且在实践上也与金属的塑性行为不符。本项目借助分析铝、铁、钛等多种典型金属证实泰勒原理不符合金属真实的塑性变形行为；进而在确切的物理基础上提出了以金属多晶体塑性变形过程中晶粒间的弹性和塑性交互作用与变形外力以很简单的方式共同决定晶粒变形行为的反应应力理论和相应模型；其特点在于客观合理、物理基础明确、自然简洁，克服了泰勒原理在科学上的疏漏。研究中观察了以位错滑移为主要塑性变形晶体学机制的工业纯铝、高锰钢、奥氏体不锈钢等面型立方金属，低碳钢、无间隙原子钢、取向电工钢、无取向电工钢、金属钨等等体心立方金属，以及两种密排六方工业纯钛的轧制变形行为、取向演变和织构形成过程；并在适当考虑可能的机械孪生的前提下借助反应应力理论和模型对其变形行为和变形织构进行了模拟计算。结果显示，新的理论模型能更贴切地反映出金属轧制变形的特殊性；模拟计算的轧制织构不仅在织构类型和织构位置与试验观察相符，而且所模拟的织构密度峰值也符合试验观察。所提出的理论模型还可以同时表达金属特定的不均匀变形过程，乃至不同类型塑性变形晶体学体系各自的加工硬化过程及其复杂的交互作用。项目研究工作推动了金属塑性变形理论的完善与健康发展，项目研究成果可在金属加工工业领域应用于预测和控制金属制品的变形与成型、性能及各向异性、取向演变和变形织构等，促进相关生产的高效节能化发展。