Casting of High Alloy Steels in the Mushy State

Abstract

In order to broaden the field of application for the innovative thixocasting process, much research is dedicated to the thixocasting of high melting point alloys. The wide property range of modern high alloy steels combined with the productive semi-solid die casting process opens up new fields of application. The Foundry Institute of the Aachen University has therefore been concentrating on the research of the possibilities and limits of high pressure die casting of high alloy steels in the semi-solid state. This paper gives an overview of the current work dedicated to thixocasting of steel alloys by a high pressure die casting machine at the Foundry-Institute of the Aachen University of Technology.In order to understand and describe the material properties in the semi-solid state, basic test specimens have been investigated. Weak points of tool preheating as well as directional solidification of the produced parts can be controlled by numerical simulation of the temperature distribution inside the dies. In consideration of the outstanding flow properties of semi-solid steels more complex geometries with accurately defined applications are now being investigated. Extensive metallographical analyses of the pre-material, the reheated billets and the produced parts have been done to evaluate the viability of the process. The mechanical properties of the specimens outline the outstanding potential of the thixocasting process.

Influence of Reinforcement Particle Parameters on the Homogeneity of Particle Distribution in Semi-Solid Formed Aluminium Matrix Composites

“…al. [16], the solid phases in a semi-solid melt tend to refine under shear loads and thus to fill smaller wall thicknesses, the size of the SiCp does not decrease due to the high hardness, resulting in segregation of matrix alloy and reinforcement. Since the particle size distribution of a monomodal powder has also an amount of smaller particles than the mean particle diameter, the effect can be investigated here as well.…”

Semi-solid Processing of Alloys: Principles, Thermodynamic Selection Criteria, Applicability

“…[11][12][13][14] Up to now, only a few attempts have been made to develop alloys specifically for the particular demands of SSP. 7,15) The influence of variations of the alloy composition on SSP has been studied by Kaufmann et al 16) Before the experimental development work on a particular system starts, thermodynamic calculations have proven useful to check whether the alloy may be expected to meet the requirements of SSP with respect to its phase constitution during solidification.…”

Selection of Suitable Tool Materials and Development of Tool Concepts for the Thixoforging of Steels

“…Therefore, for the thixoforging of steels, special tool materials, coating combinations and tool designs have to be developed to fulfil these special requirements. Up to now, only a few steel components have been produced on a laboratory scale [5][6][7] .…”