超细晶纯镍热稳定性的研究
关键词 等通道径角挤压 液氮冷轧 超细晶镍 热稳定性
毕业论文设计说明书外文摘要
Title Thermal stability of ultrafine-grained pure Nickel
Abstract
Pure nickel (99.99%) was processed by Equal channel angular pressing with route Bc up to 1,2 and 8 passes. Liquid nitrogen rolling (LNR) was also used to process coarse grained (CG) nickel and ultra-fine grained nickel (8p). The microstructure of deformed samples were characterized by TEM and EBSD. Mechanical properties (strength and fracture) of deformed samples were tested and analyzed. Thermal stability of nickel with eight passes (8p), liquid nitrogen rolling (LNR 87%) and 8p+LNR87% were investigated through isothermal annealing and isochronal annealing. The EBSD results and microhardness evolution of samples after heat treatment were recorded and used to evaluate the softening behavior. Results showed that liquid nitrogen rolling can improve the grain refinement of ECAPed sample from ~500nm to ~100nm, however the thermal stability of 8p+LNR87% is lower than other samples. The microstructure evolution of nickel during annealing is related to discontinuous recrystallization, and the high dislocation density provides the driving force compared with the grain boundary curvature.
Keywords Equal Channel Angular Pressing Liquid Nitrogen Rolling Ultrafine-grained pure Nickel Thermal stability
目 次
1 引言 1
1.1研究背景 1
1.2 等通道转角挤压法(Equal channel angular pressing, ECAP) 2
1.3 液氮冷轧（Liquid Nitrogen Rolling,LNR） 4
1.4 常见超细晶金属材料热稳定性的研究现状 5
1.5 本次毕业设计探索的内容、目标及创新性 5
2 实验材料及方法 7
2.1 实验材料 7
2.2 实验路线及方案 7
2.3 实验设备 8
2.4 实验方法 9
3 变形组织和性能 13
3.1 8p、LNR87%和8p+LNR87%变形组织观察 13
3.2 8p、LNR87%和8p+LNR87%力学性能 13
3.3 8p、LNR87%和8p+LNR87%拉伸试验断口分析 14
4 超细晶纯镍热稳定性分析 15
4.1 8p、LNR87%和8p+LNR87%退火组织观察 15
4.2 超细晶纯镍退火显微硬度变化 17
4.3 超细晶镍再结晶机理分析 20