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analysis area (numerous images were taken per sample) used to determine pore characteristics.


One of the porosity characteristics of particular interest is the equivalent pore diameter. A preliminary analysis of the values listed in Table 7 indicated little to no entrainment oc- curred during the filling of the B-S-710 and B-F-710 plates. This thought is drawn from references which indicate a range for the diameter sizes of entrained bubbles is approxi- mately (0.5 – 5 mm).1


The aspect ratios of the pores were found to be within a range of 1.6-1.8. The results of the SDAS, aspect pore ra- tio, and equivalent pore diameter tend to correlate with the thoughts that the pores are not purely gas-induced and the filling process is relatively unimportant for the formation of the small amounts of porosity found in the samples.


Metallography - Set 2


The inner surfaces of the samples tended to have similar dendritic features and apparent areas of porosity; however, preliminary inspection of the fine pore sizes would gener- ally indicate a quiescent filling compared with typical grav- ity systems,1


as found in the metallographic analysis of the


first set of castings. Figure 11 illustrates characteristic mi- crostructural images of the samples analyzed.


Confluence Welds From casting Set 1, three of the castings produced using the slow fill profile contained confluence welds. The first, used for mechanical testing, has been discussed in the Ex- perimental Procedures section. Now the latter two will be examined in depth. The confluence weld locations of these plates are shown in Figure 12.


(a)


(b)


(c)


(d)


Figure 11. Characteristic optical microscopy images of specimens: (a) A1_2-12; (b) A2_1-16; (c) B_2-10; (d) B0_2-1 showing a largely free of porosity dendritic structure.


74 International Journal of Metalcasting/Spring 2012


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