Gm Global Technolgoy Operations, Inc.

James W Knight

Qigui Wang

Wenying Yang

Devin R Hess

A quantitative metallographic method to measure skin layer thickness in high pressure die cast aluminum components. Because the faster-cooling skin layer region exhibits a higher volume fraction of eutectic phases than that of a slower-cooling inner region, measurements showing such higher eutectic phases can be used to quantify such layer thickness. An image at various thicknesses of a location of interest in a cast component sample is first obtained using an image analyzer, from which eutectic volume fractions within each of the received images may be determined. Comparisons of the determined volume fractions can be made against a known or predicted quantity for a particular alloy composition, and then correlated to the skin layer thickness via differences between the received or measured quantities and those of the known standard.

Method to determine skin-layer thickness in high pressure die castings

A method to automatically quantify dendrite arm spacing in dendritic microstructures. Once a location of interest in a cast material specimen has been identified, the information contained in it is automatically analyzed to quantify dendrite cell size information that is subsequently converted into a quantified dendrite arm spacing through an empirical relationship or a theoretical relationship. In one form, the relationship between DCS and DAS is such that the DAS in dendritic structure of cast aluminum alloys may be automatically determined from the measurement of one or more of dendrite cell size and the actual volume fraction of the eutectic phases in the local casting microstructure. Non-equilibrium conditions may be accounted for in situations where a theoretical volume fraction of a eutectic phase of the alloy in equilibrium condition is appropriately modified. Thus, in situations where equilibrium conditions&#x2014;such as those where the casting is cooled very slowly during solidification&#x2014;does not apply (such as during rapid cooling and consequent solidification), the eutectic measured in the non-equilibrium condition, which can be smaller than the theoretical value in equilibrium, can be accounted for.

Method for automatic quantification of dendrite arm spacing in dendritic microstructures

A quantitative metallographic method to measure pore sizes and pore distributions in cast aluminum components. An image of a location of interest in a cast component sample is first obtained using an image analyzer. Spacing criteria, such as a measure of the secondary dendrite arm spacing, may be used with the received image to provide evidence of pore clustering. This allows the system to performing calculations to determine if multiple pores can be clustered or grouped together as a single pore in three-dimensional space. From this, the total area of the pores in each of these groups or clusters is calculated and used as a representation of the pore area for that cluster. In general, pore size and pore distribution measurements in cast components achieved by the present invention show accurate predictions of pore size and spacing, and in particular evidence a reduced tendency to under-predict the size and distribution of actual pores.

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Davison, MI, United States of America

James W Knight