Stacking faults in Zr(Fe, Cr)2 Laves structured secondary phase particle in Zircaloy-4 alloy

Understanding the formation mechanism of stacking faults in secondary phase particles.

Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys

The effect of cooling rate on microstructure and microsegregation of three commercially important magnesium alloys was investigated using Wedge (V-shaped) castings of AZ91D, AM60B, and AE44 alloys. Thermocouples were distributed to measure the cooling rate at six different locations of the wedge casts. Solute redistribution profiles were drawn based on the chemical composition analysis obtained by EDS/WDS analysis. Microstructural and morphological features such as dendrite arm spacing and secondary phase particle size were analyzed using both optical and scanning electron microscopes. Dendritic arm spacing and secondary phase particle size showed an increasing trend with decreasing cooling rate for the three alloys. Area percentage of secondary phase particles decreased with decreasing cooling rate for AE44 alloy. The trend was different for AZ91D and AM60B alloys, for both alloys, area percentage of β-Mg17Al12 increased with decreasing cooling rate up to location 4 and then decreased slightly. The tendency for microsegregation was more severe at slower cooling rates, possibly due to prolonged back diffusion. At slower cooling rate, the minimum concentration of aluminum at the dendritic core was lower compared to faster cooled locations. The segregation deviation parameter and the partition coefficient were calculated from the experimentally obtained data.

The Hayashi-nishi Method for Measurement of Mixing:Computer-Generated Morphologies and Impact-Modified Polymers

In this work we apply the Hayashi-Nishi method for quantitatively analyzing the state of mixing of a secondary component in a polymeric matrix. We (1) evaluate the method using computer-generated morphologies and (2) compare the state of mixing of a core-shell impact modifier in polymers having differing affinity for the impact modifier. In the Hayashi-Nishi method two numbers, related to dispersion and distribution, are required to quantify the state of mixing of a secondary phase in a polymeric matrix. The 5-parameter in the Hayashi-Nishi method is defined asThe Ai's are the areas of each individual secondary phase particle or aggregate and nis the number of such particles in the image. S is related to the size distribution of these aggregate areas and is a measure of dispersion of the secondary phase in that particular image.