A CRYSTALLOGRAPHIC MODEL FOR THE ORIENTATION DEPENDENCE OF LOW CYCLIC FATIGUE PROPERTY OF A NICKEL-BASE SINGLE CRYSTAL SUPERALLOY

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晶粒的取向和变形性质对双晶体循环变形影响的模拟研究

应用晶体细观力学方法，分析了双晶体循环变形过程中组元晶粒取向及其变形性质（Ｂａｕｓｃｈｉｎｇｅｒ效应和循环硬化）的影响，发现双晶体的反向屈服及循环硬化行为为主要由组元晶粒性质支配，晶间内应力的影响是次要的，晶粒取向对宏微观应力应变行为有重要的影响，取向对称性较弱或罗硬差别较大的双晶体晶界影响较大。  

镍基单晶合金蠕变变形过程的描述

基于强化相γ’的筏化－解筏和粗化的细观过程，本文推导了一组用于描述基单在合金蠕变变形过程的蠕变方程，并在９５０℃和７６０℃标定了国产ＤＤ３镍基单晶合金不同晶体取向的模型参数，与实验结果比较，所提模型可以准确地描述蠕变的主要阶段。  

表面微空洞长大和相互作用的晶体有限元分析

通过建立空洞长大和相互作用的3D模型，采用晶体塑性有限元模拟研究了FCC晶体表面空洞的长大和相互作用行为，分析了晶体取向和微空洞在表面的深度变化对表面空洞长大和相互作用的影响。模拟结果表明：晶体取向除了影响空洞形状和长大方向外，还会影响空洞长大速度；总体而言，在固定位移边界条件下硬取向晶粒表面的空洞长大和相互作用大于软取向。随着空洞在单晶体表面深度的增加，空洞周围的最大塑性变形增加，变形局部化更加严重，空洞长大速度增加。  

Simulation of cyclic deformation of bicrystals: Effects of orientation and deformation properties of constituent grains

The cyclic deformation of aluminium bicrystals was numerically simulated by using a crystalline micromechanical approach to study the effects of crystallographic orientation and deformation properties of constituent grains. Both the macro-and micro-stress-strain responses were analyzed. It was shown that the whole Bauschinger effect and cyclic hardening behavior of bicrystals is primarily controlled by the corresponding properties of the constituent grains, and that the effects of internal stresses induced by the grain boundary and the interaction between grains are secondary. The crystallographic orientation of constituent grains was also shown to have significant influence on the macro-and micro-mechanical behavior of the bicrystals. There were smaller symmetry in the orientation or greater difference in the strength between grains and more remarkable GB effects.