A Comparison Between Semisolid Casting Methods for Aluminium Alloys

Abstract

Semisolid casting of aluminium alloys is growing. For magnesium alloys, Thixomoulding became the dominant process around the world. For aluminium processing, the situation is different as semisolid processing of aluminium is more technically challenging than for magnesium. Today three processes are leading the process implementation, The Gas-Induced Superheated-Slurry (GISS) method, the RheoMetal process and the Swirling Enthalpy Equilibration Device (SEED) process. These processes have all strengths and weaknesses and will fit a particular range of applications. The current paper aims at looking at the strengths and weaknesses of the processes to identify product types and niche applications for each process based on current applications and development directions taken for these processes

In-Production Rheometry of Semi-Solid Metal Slurries

“…The microstructure analysis revealed a typical microstructure from a RheoMetal processed material. The microstructure shown in Figure 3 is similar to an equiaxed gravity die-cast microstructure and does not display the typical globular microstructure commonly found in semi-solid processed materials [1][2][3]. The RheoMetal process is signified by a rapid slurry generation to a high fraction, where the trade-opp to productivity is a less globular microstructure.…”

“…At the onset of solidification, the viscosity increased from the fully molten state with just below 0.04 Pa s and steadily increased to just below 5 Pa s near the eutectic temperature at a shear rate of 100 1/s, which is approximately a factor twice as high than what was presented by Modigell et al [6]. Even though Das et al [17] used dynamic measurements, time scales may fit a process, such as the SEED process, but are far too long compared to GISS and the RheoMetal process [2].…”

“…Semi-solid aluminium alloy processing (SSM) has advanced into a more mature process with many applications [1,2]. SSM processing was introduced by Spencer [3], and it was initially identified as a fundamental discovery leading to a strong development of research into the rheology of SSM slurries behaviour [4][5][6].…”

“…In all studies involving rheological characterization, precision instruments are used, and results are obtained with high precision. The main issue in industrial practice is that the slurry structure and grain formation and properties are far from the particle sizes and time scales found in industrial processing, where the range of treatments is from a few seconds up to just below 300 s [2]. Transient behaviour has been studied, but the initial creation of slurries for the precision rheometers inhibits a one-to-one match of the slurry structures [6].…”

“…Grain refined A356 (GR A356),2 Magnetohydrodynamically stirred A356 (MHD A356),3 Above the melting point.…”