3D相场模拟研究Ti-6Al-4V合金片层组织形貌的影响因素

3D Phase Field Simulation of Factors Influencing the Microstructure Morphology of Lamellar Ti-6Al-4V Alloy

Ti-6Al-4V是典型双相钛合金,不同的微观组织决定其力学性能,但由于缺少晶界α、片层α、α侧枝等相对取向关系的三维信息,难以实现组织的精准调控。本工作基于Pandat和Thermo-Calc热力学数据以及DICTRA动力学数据,采用相场法模拟Ti-6Al-4V合金片层α组织的三维形貌。研究了在820℃热处理温度下,界面能各向异性对片层α生长的影响并分析了不同时刻的溶质场。结果表明,片层α组织的演化形貌受界面能各向异性的影响,界面能各向异性由0.4∶0.1∶1.0增长到0.8∶0.1∶1.0时,片层α由粗大棒状转为细长针状。界面能各向异性越大,片层生长的速率越快。不同界面能各向异性条件下片层α组织的主要差别在于片层的疏密程度和生长速度,而生长方向基本无异,单片层的宽度逐渐变宽。相场模拟结果与实验结果吻合较好,片层组织的三维模拟结果展示出比扫描电镜二维照片更丰富的片层侧枝细节。在3D模拟中可观测到晶粒不同位置处侧枝的形貌。结果表明,侧枝与主片层之间的夹角既有实验观测到的30°,还存在任意角度。

Ti-6Al-4V,a typical dual-phase titanium alloy,has mechanical properties largely determined by its microstructures.However,the absence of three-dimensional(3D)information regarding the relative orientation relationships of grain boundaryα,αlamellae,andαside branches,hinders precise microstructure control.In this study,using thermodynamic data from Pandat and Thermo-Calc,along with kinetic data from DICTRA,the 3D morphology ofαlamellae in Ti-6Al-4V alloy was simulated via the phase field method.This study simulated the influence of interfacial energy anisotropy on the growth ofαlamellae at a heat treatment temperature of 820°C and analyzed the corresponding solute field.The findings reveal that interface energy anisotropy considerably affects the morphology ofαlamellae.When the anisotropy of the interface energy increased from 0.4∶0.1∶1.0 to 0.8∶0.1∶1.0,theαlamellae transformed from a thick rod shape to a slender needle shape.Higher anisotropy levels lead to accelerated growth rates ofαlamellae.Variation in interface anisotropy,primarily affect the density and growth rate ofαlamellae,while their growth direction remains consistent.Additionally,the width of individual lamellae progressively widens under different interface anisotropies.The phase-field simulation results align closely with experimental findings.Notably,the 3D simulation results ofαlamellae organization offer more detailed insights into the side branches ofαlamellae than two-dimensional(2D)SEM images.In 3D simulation,it can be observed the growth morphology of side branches at different positions of grains.The results indicate that the angle between the main lamellae and the side branches includes experimental observations of 30°and random angles.