密排六方钛合金宏观织构的超声分析方法

快速无损伤的测量正交宏观对称的六方晶系多晶体材料织构特征,在材料学方面成了亟待解决的难题。通过建立晶粒取向分布函数、多晶材料等效弹性常数和超声波在材料近表面的传播特征三者的关系,来确定晶粒取向分布函数的五个织构系数W₂₀₀,W₂₂₀,W₄₀₀,W₄₂₀,W₄₄₀,构建极图并分析材料的宏观织构特征。其中,采用的两种波型分别是:小角度临界值纵波和瑞利波,而超声波传播特征主要以研究相速度在材料主平面上随传播角度的变化为主。对圆饼状TA19钛合金锻件进行了测量分析,结果显示:单一方向的声速C扫图可以反映出TA19钛合金锻件各位置的织构差异;圆饼状TA19钛合金锻件在以圆心为中心的不同半径的圆周处有着不同的织构特征;五个织构系数分别反映出圆饼状TA19钛合金锻件不同位置处的织构差异,尤其W₂₂₀,W₄₂₀,W₄₄₀三位织构系数差异更为明显。

Ultrasonic analysis of macro-texture for hexagonal titanium alloy

Fast and non-destructive measurement of the texture characteristics in hexagonal polycrystalline aggregates with orthorhombic symmetry has become an urgent problem in materials science.In this paper,the five texture coefficients W200,W220,W400,W420,W440 of the grain orientation distribution function were determined by establishing the relationship among the grain orientation distribution function,the effective elastic constant of polycrystalline materials and the propagation characteristics of ultrasonic waves near the surface of the material.Then the pole figure was established and macro texture characteristics of the material were analyzed.Among them,the two wave types used are:the longitudinal wave of small incident angles and the Rayleigh wave,and the characteristics of ultrasonic propagation mainly focus on the study of phase velocity changes with the propagation angle on the main plane of the material.The results show three pieces of information.First,the image of C-scan of velocity in single direction can reveal difference of texture in forgings of TA19 titanium alloy;Second,disc-shaped TA19 titanium alloy forgings have different texture characteristics at the circumference of different radii centered on the center of the circle;Third,The five texture coefficients can respectively reflect the texture difference at different positions of the disc-shaped TA19 titanium alloy forgings,especially the W220,W420,W440 three-position texture coefficients are more obvious.