Solid State Phenomena Vol. 348

Abstract: The current market change of aluminium HPDC castings started with the “Dieselgate”. First, there was a shift from diesel to petrol engines. In the second step, hybrid and battery-powered cars gained significant market shares in sales statistics. Therefore, lucrative powertrain components are falling away. As powertrain foundries still want to utilize their machines to capacity, they are pushing into the structural castings market. As a result, there is an oversupply of casting machines here, which massively depresses prices and, thus, margins for tenders. With rising energy costs, these declining margins were eaten up, bringing foundries into crisis. Implementing Rheocasting at the existing die-casting cells is the solution to move into new market shares that are now not accessible in conventional HPDC.One of the new applications is electronic housings, high wall thickness parts, and fatigue bearing parts. These parts are commonly manufactured in sand or gravity castings because of their high wall thickness and low tolerance of porosity. Rheocasting is the perfect process for high-wall thickness components. Because of the semisolid melt preparation and the lamellar filling behavior, these components can be manufactured from the same alloy without pores or voids.This flow behavior of the semisolid slurry also results in a longer flow length. Slower casting speeds and lower pressure settings result in lower clamping forces. This gives an advantage in production costs and targets battery constructions made of castings and sheet metal. Structural battery housings must be leak-tight, even in a crash event. Having it in one casting instead of an assembly reduces the leakage area and improves crash performance.Another industry that relies on Rheocasting is the telecommunications industry. The power electronics in these 5G modules are significantly larger and generate much more waste heat. Until now, many antennas have been actively cooled or milled from a block of aluminum. The milled housings are significantly too expensive to enable series production. Therefore, the goal is to reproduce the passively cooled modules in die casting. Due to the process, the thermal conductivity in conventional HPDC is around 120 to 130 W/m*K. Similarly, no slim cooling fins can be formed. Only the Rheocasting process makes it possible to cast other alloys with low proportions of alloying elements, such as AlSi2Mn. This allows fins with a wall thickness of down to 0.4 mm and thermal conductivity of up to 190 W/m*K.Rheocasting enables access to market segments out of reach. These bring an unbeatable cost advantage against the current suppliers: gravity and sand casters. The low cycle time in Rheocasting brings back the high margins needed to sustain the business. Also, these products can be delivered with even better properties on smaller casting machines.

Abstract: Injection molding has proven for over 150 years to be the efficient mass manufacturing technology of net-shape components from plastics, however, its application to metallic alloys, despite four decades of commercialization, still creates challenges. Although early designs assumed a direct replacement of plastic with magnesium, subsequent research revealed essential differences in machinery and processing requirements, imposed by metallic alloys. The key discovery revealed that the dendrite-to-globule transformation during coarse particulate melting is caused by strain induced melt activation (SIMA) due to feedstock deformation imposed at their manufacturing stage, not due to the injection screw shearing during processing. As a result, the process control parameters and the screw and barrel design can be optimized with a focus on other screw functions. That discovery also led to the simplified machinery designs, eliminating the complex injection screw, and replacing it with a simple plunger.

Abstract: The Al-Si-Mg family is the preferred group of casting alloys due to their excellent castability, good mechanical properties and corrosion resistance. The ENAC-AlSi7Mg0.3 (A356) alloy has been used for decades to produce structural parts such as automotive wheels or suspension parts. However, this alloy cannot be used for high pressure die casting (HPDC) due to die soldering issues. Casting parameters in rheocasting differs greatly from those in HPDC. The lower injection temperature and lower intensification pressure reduce the reactivity between the mould and the aluminium. This lower interaction allows the injection of permanent mould alloys using HPDC. The objective of this work is to compare current structural alloys with rheocasting. A wide range of alloys in the Al-Si-Mg (-Mn) family were cast using the RheometalTM semi-solid technology in addition to ENAC-AlSi7Mg0.3 (A356) used as a comparison basis. Firstly, it was proven that ENAC-AlSi7Mg0.3 (A356) can successfully be cast using rheocast HPDC. Secondly, the impact of magnesium and manganese were studied. Magnesium has a great impact on strength while manganese can further improve the strength by controlling the iron phase morphology. This work proves that various types of alloys can be cast using rheocast HPDC.

Abstract: Structural high vacuum die casting has been growing significantly over the past decades. It is typically done with special (primary type) alloys, special melt treatment practices, high vacuum, a carefully engineered die casting process applying many best practices in our industry. Structural die castings are growing in size and complexity and die casting machines are getting bigger and bigger - and those castings are becoming a significant challenge with current technologies. It was now found that Rheocasting - a process of preparing a semi-solid slurry (with 30-45% solid fraction) that is injected slower and in a laminar way into the cavity, can take structural die casting to completely new heights, enable the casting of parts that would otherwise be impossible to cast and at the same time reduce or eliminate some of the current problems of structural die casting. With Rheocasting, lower purity (secondary) aluminum alloys can be used and excellent properties can be achieved as cast and heat treated (T5, T6/7). Rheocasting has had a breakthrough in the telecom and other industries, but it has now been optimized to become an essential tool in the toolbox of making structural castings. This paper shows the developments that lead to the successful series production of a large (about 4’ long) hinge pillar for an Electric Vehicle (EV). It explains the challenges and how they were overcome, and some of the possibilities of the process regarding alloys, heat treatments and achievable properties. It also shows how Rheocasting can help die casters produce more complex (thin and thick walled) and very large castings with the highest integrity. It can replace structural low-pressure permanent mold (LPPM) castings and reduce wall thickness, improve tolerances and make them more economical. Rheocasting can enable die casters to enter this new market of structural castings including Gigacastings, produce parts previously thought impossible to cast (and on much smaller machines than thought), and expand the growing structural die casting market even faster and further.

Abstract: Objective of the paper is to present the latest applications of GISS technology, a little more than six years since the launch in the die casting industry. Industrial applicability and robustness of the solution have been the main targets of GISSCO development which is focussed on providing a technology appliable to mass production with short lead time and cost effectiveness. Based on the concepts of viscosity control and feeding compensation the GISS technology can lead to reduction of production costs (energy, lubrication, waste disposal, die life extension) as well as increase of the casting quality. Life Cycle Inventory and Carbon Footprint calculation of a case study are presented.