搅拌摩擦焊接Ti-6Al-4V钛合金晶粒生长的数值模拟

Numerical simulation of grain growth of Ti-6Al-4V alloy in friction stir welding

基于DEFORM-3D有限元软件建立Ti-6Al-4V钛合金工件的搅拌摩擦焊接过程的完全热力耦合模型,提取工件温度场基于蒙特卡洛法模拟焊后工件截面的晶粒尺寸及各相体积分数的分布规律。搅拌区晶粒受摩擦搅拌作用破碎至细小晶粒为初始生长状态。结果表明:热影响区晶粒在母材尺寸上继续生长,Ti-6Al-4V钛合金不发生相变;搅拌区温度升高时晶粒会转变为β相,下降时会在β相晶粒边界析出α相,且α相粒子向β相粒子内部生长并长大,较高冷却速度下α相向β相晶粒内部生长为针状。

Based on finite element software 3D-DEFORM, a thermo-mechanical model of Friction Stir Welding （FSW） of Ti-6Al- 4V was established. The predicted temperature was used for the simulations on grain sizes and the volume fractions in FSW by use of Monte Carlo method. The grains in the stirring zone were stirred into small grains which is treated as the initial state for the further grain growth simulations. Results indicate that there is no phase transformation in the heat affected zone. But for the stirring zone, β phase can be formed in the heating process. In the cooling process, α phase can be generated on the boundaries of β phase and grows into the interior of the β phase grain. Needle like structure can be formed at higher cooling rate.