Automatic Determination of Secondary Dendrite Arm Spacing in AlSi-Cast Microstructures

Christian Gawert,Rüdiger Bähr

doi:10.3390/ma14112827

Abstract

A new procedure for the automatic measurement of the secondary dendrite arm spacing (SDAS) from microscopic images is presented. The individual primary and secondary dendrite arms are identified through suitable segmentation techniques and clustered in such a way that dendritic structures are obtained suitable for SDAS measurement. The algorithms are applied to two different hypoeutectic aluminum cast alloys, and the quality of the measurements obtained is assessed through a comparison to manually measured SDAS values. A good agreement between the automated measurements and the distribution of manual measurements is found for both cast structures considered. In addition, a decrease in computation time is observed which allows for an increase in measurement density that is used to characterize the microstructures.

Highlights

Automatic Determination ofThe significance of lightweight engineering increases continuously, in the fields of automotive and rail vehicle industry
Both approaches avoid the explicit identification of dendritic structures that are suitable for secondary dendrite arm spacing (SDAS) measurements
We present a method by which the individual dendrite arms can be detected, scored and grouped in such a way that dendritic structures can be identified that are suitable for the direct SDAS measurement

Summary

Introduction

The significance of lightweight engineering increases continuously, in the fields of automotive and rail vehicle industry. The market for aluminum casting alloys is growing. AlSi alloys are used for automotive cast products because of their good castabillity. Hypoeutectic AlSi cast alloys solidify usually in dendritic structures. In order to quantify those dendritic structures, the secondary dendrite arm spacing (SDAS) is commonly used. This SDAS value is known to correlate to a variety of different solid state properties of the cast, as for example the solid solution and age hardening, as well as the shrinkage or gas porosity. The corrosion properties were shown to be related to the SDAS [6,9,10]

Methods

Results

Conclusion