晶界结构对奥氏体不锈钢低周疲劳性能的影响
（1）冷轧变形经过947℃退火处理28h的形变热处理工艺使304奥氏体不锈钢母材Σ3n晶界含量从27%增加到40%，得到晶界特征优化的试样，Σ3n晶界可以有效打断一般大角度晶界的网络连通性；
（2）晶界特征优化不会改变304奥氏体不锈钢的循环软硬化特性。虽然初始循环应力不如母材，但在循环一定周次后直到破坏，晶界优化后的试样循环强度高；
（3）由于低能特殊晶界数量的增加，使得晶界特征优化后的疲劳过渡寿命提高了约14倍，疲劳寿命提高了1倍，大大的改善了不锈钢的低周疲劳性能。
关键字：晶界 多晶体金属 奥氏体不锈钢 低周疲劳 晶界控制与设计
毕业设计说明书（论文）外文摘要
Title The effect of grain boundary in the characters of low-cycle fatigue in Austenitic Stainless Stell
Abstract
Polycrystalline metal material is one of the main research objects in the material science. And the grain boundary and the character of the polycrystalline metal material strongly influence grain boundary migration, the cluster phenomenon of the solute atom in grain boundary and the materials mechanical and physical properties etc. According to some problems appearing in the cycle process when the Austenitic Stainless Steel is in the low-cycle fatigue, this article study the 304Austenitic stainless steel’s low cycle fatigue behavior from the grain boundary control. Through the reasonable heat treatment process to change the304 stainless steel microstructure and grain boundary distribution, investigates grain boundary engineering in reinforcing material fatigue properties in terms of feasibility，The main results are as follows：
（1） Deformation heat treatment process make the material’s Σ3n boundaries content increased from 47% to84%, while the Σ3n boundaries can effectively interrupt the general large angle grain boundary connectivity；
（2） The optimization of Grain boundary character does not change the circulation of 304 austenitic stainless steel and chemical characteristics. Although the initial cyclic stress don’t match previous material, but in the cycle of certain cycles until after the destruction of the grain boundary, optimized sample cycle has higher strength;
（3） Due to increase of the low energy special number of grain boundaries, the grain boundary character optimization of fatigue after transition life is increased by about 14 times, the fatigue life is improved by 1 times, greatly improved the fatigue life of stainless steel in low cycle fatigue.
Key word：Grain boundary Polycrystalline metal Austenitic Stainless Steel Low-cycle fatigue Grain boundary controlling and design.
目 次
1 引言 1
1.1 晶界工程简介 1
1.2 晶界结构 2
1.3 实现晶界工程的途径 4
1.4 材料的低周疲劳 5
1.4.1 材料疲劳概述 5
1.4.2 材料的低周疲劳 5
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