Effect of Mechanical Vibration on the Mechanical Properties and Solidification Feeding in Low-Pressure Sand Casting of Al-Cu-Mn-Ti Alloy.

Abstract

The shrinkage defects of Al-Cu-Mn-Ti alloy seriously hinder its application in high-performance engineering. In this study, mechanical vibration was introduced to low-pressure sand casting (LPSC) by a waveguide rod to eliminate shrinkage defects and improve mechanical properties. Four LPSC castings were performed by changing the solidification conditions: 20 kPa solidification pressure without and with 14 Hz vibration and 40 kPa without and with 24 Hz (the natural frequency of a casting system) vibration. The shrinkage defects, microstructures, and mechanical tensile properties at room temperature and at 2 mm/min tensile rate were investigated. X-ray detections showed that applying vibration was more effective than increasing solidification pressure in improving solidification feeding, while the most effective method was applying both simultaneously, which eliminated the shrinkage defects and increased the density by 2.7%. Microstructures exhibited that the average size of primary α-Al grains were reduced by 29.5%; mechanical tests showed that the ultimate tensile strength and the elongation increased by 21.7% and 7.8%, respectively, by applying vibration and increasing the solidification pressure simultaneously, as compared to the casting with 20 kPa solidification pressure without vibration. Mechanical vibration was conducive to mass feeding by refining the primary grains, to interdendritic feeding by reducing the threshold pressure gradient, and to burst feeding by collapsing the barrier.