Abstract:

In this work, the shear model of metal melt flowing on vibration surface is established, and coupling effects of vibration and shear on the distribution of shear stress in melt and melt solidification microstructure are analyzed. Calculation results show that the transition of melt from laminar flow to turbulent flow occurs earlier with increasing vibration frequency and vibration amplitude. In the laminar flow melt, shear stress in melt decreases with increasing vertical length, but it decreases firstly and then stabilizes with increasing flow length. In the turbulent flow melt, shear stress decreases firstly and then stabilizes with increasing vertical length, but it increases with increasing flow length. With the increase in vibration frequency and amplitude, shear stress along flow direction in laminar flow melt increases, while shear stresses along both flow direction and vertical direction in turbulent flow melt increase. Shear stress in melt decreases with increasing length along vertical direction. With the increase in flow length, shear stress decreases firstly and then stabilizes in laminar flow melt, while it increases in turbulent flow melt. With the increase in vibration frequency and amplitude, shear stress increases in laminar flow melt, while it stabilizes in turbulent flow melt. Based on theoretical calculation, the maximum shear stress in melt during vibration shear flow is always much lower than the yield strength of α-Al grain, so the shear stress induced by vibration shear flow cannot break columnar crystal, which agrees with the experiment result. So, the model can explain the shear constitutive relation of melt flow on vibration surface relatively well.

Key words: Solidification, Flow near surface, Shear, Vibration, Columnar crystal