摘要
通过力学性能测试、扫描电镜观察以及有限元模拟计算的方法,研究了全层组织γ-TiA l基合金在压缩状态下的变形及损伤机制。结果表明：较小的加载卸载应力作用下,材料的压缩性能没有受到影响,直至卸载应力超过最大压缩应力之后,由于材料内部损伤的积累程度增大,在材料内部形成主裂纹,使得有效承载面积下降,后续再加载过程中材料的断裂应力整体下降。压缩状态下：首先,随着变形程度的增加,晶粒周围出现大量的滑移线及挤出脊,滑移线和挤出脊处出现较大的裂纹,试样表面产生平行于压缩轴方向的裂纹并迅速扩展,表面裂纹面密度明显增加,45°方向上的沿层裂纹扩展程度较大,但裂纹长度仅限于晶粒尺寸的大小（100~300μm）。其次在压缩加载过程中,材料在较小的正应力作用下,观察得到表面萌生以下4种裂纹：平行于压缩轴方向的纵向沿层裂纹;与压缩轴方向成较小角度的纵向沿层裂纹;与压缩轴方向成较小角度的纵向穿层裂纹;纵向的穿晶裂纹。
The compression deformation and damage behavior of TiAl based alloys were studied by measurement of mechanical properties,SEM observations and FEM calculation.The results showed that： No appreciable effects of the preloading-unloading-reloading processes on global compression deformation behavior were produced,until compression preloading stress surpassed the maximum compression stress.Because of the accumulation of damage effects,the big main crack was formed,and then the true loading cross-section was descended,so the fracture stress was reduced when the specimen was reloaded again.Under the compression condition： firstly,surface microcracks paralleled to compression axis,which around the slip line and extrusion ridge,were produced and expanded rapidly.The surface microcracks density increased significantly.Compared with the microcracks paralleled to compression axis,the microcracks on the direction of 45° were propagated along the layer,but there was no exactly equivalent the microcracks to the grain in size（100~300 μm）.Secondly,four types of microcracks were initiated and propagated on the surface of the specimens with smaller normal stress in the compression process： longitudinal interlamellar cracks paralleled to the compression axis;interlamellar cracks inclined to the compression axis with a small angle;longitudinal translamellar cracks inclined to the compression axis with a small angle;longitudinal trans-granular crack.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2011年第3期463-468,共6页
Chinese Journal of Rare Metals
基金
国家自然科学基金资助(50905081)项目
关键词
TIAL基合金
压缩
有限元计算
变形及损伤
TiAl-based alloys
compression
FEM calculation
deformation and damage
