Solidification microstructure

Pressure testing of the finned oil cooler in Fig. 15.29 revealed leaks. Examination of the interior of the cooler after sectioning in the vicinity of the leaks revealed a small cavity in the weld zone in the corner of some fins (Fig. 15.14) and porous areas inside the channel in the welded zone in other fins. Microstructural examinations of specimens cut through the sites revealed interconnected voids resulting from either shrinkage during solidification of the weld or lack of fusion of the base metal and weld metal. 

M. D. Dupouy, B. Drevet, D. Camel. Influence of convection on the selection of solidification microstructures at low growth rates. J Crys Growth 181 45, 1997. 

M. Benes. On a computational comparison of phase-field and sharp-interface model of microstructure growth in solidification. Acta Technica CSAV 41 591,... 

The formation of the microstructure involves the folding of linear segments of polymer chains in an orderly manner to form a crystalline lamellae, which tends to organize into a spherulite structure. The SCB hinder the formation of spherulite. However, the volume of spherulite/axialites increases if the branched segments participate in their formation [59]. Heterogeneity due to MW and SCB leads to segregation of PE molecules on solidification [59-65], The low MW species are accumulated in the peripheral parts of the spherulite/axialites [63]. The low-MW segregated material is brittle due to a low concentration of interlamellar tie chains [65] and... 

The microstructure of a metal resulting from the solidification of liquid metal such that two or more distinct solid phases are formed. 

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