Ti-55511合金显微组织对其高温疲劳行为的影响  

Influence of microstructure of Ti-55511 alloy on its fatigue behavior at high temperature

作　　者：陈宇强[1] 贺梓泯 潘素平[2] 刘会群[2] 伏明珠 付永杰 李佳[1] CHEN Yu-qiang;HE Zi-min;PAN Su-ping;LIU Hui-qun;FU Ming-zhu;FU Yong-jie;LI Jia(Hunan Engineering Research Center of Forming Technology and Damage Resistance Evaluation for High Efficiency Light Alloy Components,Hunan University of Science and Technology,Xiangtan 411201,China;School of Materials Science and Engineering,Central South University,Changsha 410083,China)

机构地区：[1]湖南科技大学高功效轻合金构件成形技术及耐损伤性能评价湖南省工程研究中心,湘潭411201 [2]中南大学材料科学与工程学院,长沙410083

出　　处：《中国有色金属学报》2023年第3期767-780,共14页The Chinese Journal of Nonferrous Metals

基　　金：湖南省科技创新人才计划资助项目(2019RS2064);湖南省研究生科研创新项目(QL20220231)。

摘　　要：利用扫描电子显微分析(SEM)、聚焦离子束切割技术(FIB)、透射电子显微分析(TEM)等方法对比分析了双态及片层组织对Ti-55511合金的高温疲劳性能及其损伤行为的影响机理。结果表明:在350℃、应力比(R)为0、最大加载应力(σ_(max))为500~600 MPa的疲劳加载条件下,片层组织的疲劳寿命(N_(f))明显高于双态组织。双态组织的疲劳裂纹主要萌生于初生α相(α_(P)),而片层组织的疲劳裂纹萌生于晶界处粗大片层α相(α_(L))与β相的界面。在裂纹扩展阶段,双态组织的裂纹尖端区域出现显著的纳米晶化,导致次生α相(α_(s))粒子完全溶解并转化为β相,明显弱化了合金的抗裂纹扩展能力。由于α_(L)相对晶内变形的显著约束作用,片层组织裂纹尖端区域的纳米晶化并不明显,仍然保留了较高密度的α_(s)相粒子,因而具备较高的抗裂纹扩展能力。The fatigue properties and damage behavior of Ti-55511 alloy with bimodal and lamellar microstructures at high temperature were compared by scanning electron microscopy(SEM),focused ion beam(FIB)technologies and transmission electron microscopy(TEM).The results show that,fatigue loaded at 350℃,load ratio(R)of 0 and maximum stress(σ_(max))of 500−600 MPa,the fatigue lives(N_(f))of lamellar microstructure are significantly higher than those of bimodal microstructure.The fatigue cracks in bimodal microstructure mainly initiate from the primaryαphase(α_(P)),while those in lamellar microstructure generally nucleate at the interface between the coarse lamellarαphase(αL)andβat the grain boundaries(GBs).During the crack propagation,the significant nanocrystallization takes place at the crack-tip region of bimodal microstructure which leads to the complete dissolution and transformation of secondaryα-phase(α_(s))particles intoβ-phase.This weakens the crack growth resistance of the alloy obviously.Due to the evident fencing effect ofαL on intragranular deformation,the nanocrystallization at the crack-tip region of lamellar microstructure is not obvious,and a relatively high density ofαs phase particles are still retained.Therefore,the lamellar microstructure has a relatively higher resistance to crack growth.

关 键 词：Ti-55511合金 显微组织 疲劳性能 疲劳损伤机理 

分 类 号：TG711[金属学及工艺—刀具与模具]