显微组织对TC4ELI合金疲劳裂纹扩展路径及扩展速率的影响

来源期刊：金属学报2010年第9期

论文作者：马英杰 李晋炜 雷家峰 唐振云 刘羽寅 杨锐

文章页码：1086 - 1092

关键词：钛合金； 显微组织； 裂纹扩展路径； 裂纹扩展速率

Key words：titanium alloy； microstructure； crack propagating path； crack growth rate

摘    要：利用SEM观察了疲劳裂纹在具有片层组织的TC4ELI合金中的扩展路径,通过统计疲劳裂纹与α片层所呈的角度,分析了α和β两相晶体学取向对疲劳裂纹扩展路径的影响.基于对疲劳裂纹扩展路径的研究,测试并讨论了片层组织中晶粒和α片层对近门槛值阶段及Paris区阶段疲劳裂纹扩展速率的影响.研究表明,疲劳裂纹在片层组织中扩展时,疲劳裂纹在穿过α片层时倾向于沿平行或垂直于α片层的方向扩展,导致疲劳裂纹扩展路径每隔几个片层宽度出现扩展台阶;影响近门槛值阶段疲劳裂纹扩展速率的主要因素是α片层厚度,而与晶粒尺寸无关;在Paris阶段,晶粒尺寸、α片层厚度和片层长/宽比均对裂纹扩展速率产生影响.

Abstract: Long fatigue crack propagating path in TC4ELI alloy with lamellar microstructure was studied by SEM.Statistics of angles between cracking path and α lamella exhibits that fatigue crack is apt to parallel α lamella or cross α lamella vertically,which will induce the ladder shape of crack propagating path.The parallel and vertical propagating patterns were interpreted with the weak α/β interface and the orientation of hcp α-Ti unit cell.Analysis of crack propagating path helps to understand the effect of microstructure on fatigue crack growth (FCG) rates.FCG rates tests with different microstructures reveal that in near fatigue crack threshold (△K_th) region the thickness of α lamella is the main influential factor on fatigue crack growth rate da/dN,and the da/dN seems impervious to β grain size.However,in Paris region the FCG rates are both influenced by grain size and lamellar thickness.