镍基单晶合金中空穴绕夹杂形核及后续演化的有限元分析

Finite Element Analysis on Void Nucleation and Growth Around Inclusion in Nickel-based Single Crystal Superalloys

采用内聚力单元模拟镍基单晶合金中基体与夹杂之间的界面,对镍基单晶合金中空穴绕夹杂形核及扩张的过程进行了初步的分析。夹杂-基体界面的粘结强度不同,空穴的相对体积分数增长速度存在较大差异。粘结强度越小,空穴越容易形核,空穴扩张的速率越大;粘结强度越大,空穴越难于形核,空穴扩张的速率越小。应力三维度是空穴形核及扩张的主要驱动力,应力三维度越高,空穴形核及扩张的速率越大。应力三维度不同时,基体-夹杂界面开裂的初始位置及裂纹扩展的方式不同。在高应力三维度下空穴的演化由低应力三维度时的形状改变为主变为体积膨胀为主。Lode参数对空穴的形核过程及空穴形成后的扩张有着显著的影响。晶体取向对空穴的形核过程有着显著的影响,不同取向时基体-夹杂界面开裂的初始位置及裂纹扩展的方式不同。晶体取向对空穴的扩张有着显著的影响。在考虑镍基单晶合金的晶体取向相关性时,必须同时考虑Schmid系数、弹性模量和开动的滑移系。

The void nucleation and growth around an inclusion in nickel-based single crystal superalloys are analyzed by using the cohesive zone model to simulate the interface between the matrix and the inclusion.The strength of the interface includes its normal and shear strengths.The relative void volume fraction is noticeably different for different cohesive strengths.The smaller the cohesive strength is,the easier the void nucleation and the higher the void growth rate are.The stress triaxility is the main driving force of void nucleation and growth.The initial location of the interfacial debonding and subsequent crack propagation are different when the stress triaxility changes.At low stress triaxility,void deformation mainly exhibits itself as shape-change;at higher stress triaxility,it mainly exhibits itself as bulk expansion.Lode parameter has great effect on void growth and its shape change.The crystallographic orientation has considerable influence on void growth from initial debonding through complete separation to subsequent growth.