ABSTRACT The main objective of this paper is to demonstrate how flow and solidification simulation were used in the development of a new gating system design for three different magnesium alloys; and to determine the relative castability of each alloy based on casting trials. Prototype tooling for an existing 3- slide rear wheel drive automatic transmission case designed for aluminum A380 was provided by General Motors. Flow and solidification simulation were performed using Magmasoft on the existing runner system design using A380 (baseline), AE44, MRI153M and MRI230D. Based on the filling results, new designs were developed at Meridian for the magnesium alloys. Subsequent modeling was performed to verify the new design and the changes were incorporated into the prototype tool. Casting trials were conducted with the three magnesium alloys and the relative castability was evaluated. The conclusion of the study was that all three alloys were castable; however, there were significant differences between the alloys with respect to surface and internal imperfections based on the runner design used in the trials. In addition, it was found that different gating techniques are needed when casting the MRI alloys. INTRODUCTION Over the past 10 years, Meridian has conducted extensive casting trials to develop our knowledge on the castability of various high temperature low creep alloys for powertrain applications1. This work has enabled Meridian to rank these alloys on a relative scale and allowed for the propercharacterization, selection and use of these alloys for new applications. The purpose of this study was three-fold; 1) to design a magnesium gating system for a 3-slide automatic transmission die-cast tool which was originally designed for A380 aluminum alloy, 2) evaluate three high temperature low creep alloys, namely; AE44, MRI230D and MRI153M, in terms of overall castability and 3) to correlate and assess the capability of the current technology to predict casting anomalies. The project description is shown schematically in Figure 1. Effect of Different Magnesium Powertrain Alloys on the High Pressure Die Casting Characteristics of an Automatic Transmission Case2010-01-0409 Published 04/12/2010 John Jekl and Richard D. Berkmortel Meridian Lightweight Technologies Inc. Paula Armstrong General Motors LLC Copyright © 2010 SAE InternationalDownloaded from SAE International by University of Minnesota, Monday, July 30, 2018Figure 1. Project description from beginning to end. GATING DESIGN FOR MAGNESIUM BENCHMARKING THE ORIGINAL DESIGN Flow simulation was utilized to benchmark the filling and solidification of aluminum and magnesium using the original runner design as-received. For all simulations, the overflow and venting configuration remained unchanged. The results of the initial studies are shown in Figure 2. The aluminum filling pattern shows a relatively even filling profile and uniform metal temperature; however, the magnesium simulation shows a more turbulent filling pattern with areas of low metal temperature relatively early in the sequence. These simulations confirmed a re-design of the runner system would be ideal to create a more uniform filling scenario. <figure 2 here> GATE AND RUNNER ANALYSIS The new magnesium runner design was progressed using standard analysis techniques for AE/AM/AZ alloys. The iterations of the design are shown in Figure 3 which increase in gate area from the original design on the left (5.6 cm2) to the middle (8.5 cm2) and the final design (12.0 cm2) on the right. The final design yielded an average gate velocity of 48.7 m/s with a cavity fill time of 75ms which was within an acceptable range for conventional magnesium HPDC alloys. Figure 3. Progression of the magnesium runner design (original aluminum design on left, alternative magnesium design in middle, final magnesium design on the right). Once the runner design was completed and the tooling updated, the casting trial was conducted