The Role of Acoustic Pressure during Solidification of AlSi7Mg Alloy in Sand Mold Casting

Abstract

New alloy processes have been developed and casting techniques are continuously evolving. Such constant development implies a consequent development and optimization of melt processing and treatment. The present work proposes a method for studying the influence of acoustic pressure in the overall refinement of sand cast aluminum alloys, using and correlating experimental and numerical approaches. It is shown that the refinement/modification of the α-Al matrix is a consequence of the acoustic activation caused in the liquid metal directly below the face of the acoustic radiator. Near the feeder, there is a clear homogeneity in the morphology of the α-Al with respect to grain size and grain circularity. However, the damping of acoustic pressure as the melt is moved away from the feeder increases and the influence of ultrasound is reduced, even though the higher cooling rate seems to compensate for this effect.

Casting and Forming of Advanced Aluminum Alloys

“…For that, a combination of as-cast and semisolid casting using a cooling slope processed by equal channel angular pressing (ECAP) was used. Eskin and Wang [3], Kudryashova et al [4] and Puga et al [5] applied the ultrasonic vibration to study the effect of ultrasonic melt treatment in the solidified microstructure of aluminum alloys. The role of the roll-separating force in the high-speed twin-roll casting of aluminum alloys was examined by Kim et al [6].…”

Ultrasonic Cavitation Treatment of Metallic Alloys

“…The alloys and pure metal ingots were cast from commercial purity Al (99.7%), high purity Zn (99.995%), commercial purity Mg (99.91%), copper (99.9%) and silicon (99.4%). Al alloys with varying concentration of Si [45], Cu [37,51,52] and Mg [49] were cast with and without UST. Master alloys of Al3Ti1B and Mg-25Zr were introduced into the melt to understand the effect of nucleant particles [6,46].…”

“…The Neppiras-Noltingk model does not account for acoustic radiation, which is crucial at high forcing pressures. Other authors also used a linear acoustic propagation model to study the treatment of AlSi7Mg alloy melt in sand casting, even though pressures larger than 2 MPa have been predicted [51]. A linear model was also employed to compute the acoustic pressure field in a SCN-1 wt% camphor alloy, which is often used as a transparent analogue to aluminium melt [13,52].…”

Numerical Modelling of the Ultrasonic Treatment of Aluminium Melts: An Overview of Recent Advances

“…The Neppiras–Noltingk model does not account for acoustic radiation, which is crucial at high forcing pressures. Other authors also used a linear acoustic propagation model to study the treatment of AlSi7Mg alloy melt in sand casting, even though pressures larger than 2 MPa have been predicted [51]. A linear model was also employed to compute the acoustic pressure field in a SCN-1 wt% camphor alloy, which is often used as a transparent analogue to aluminium melt [13,52].…”