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Unformatted text preview: Solution: HW3 WS06 Q1) Solution : a) b) from figure 3-15 a and b of Schey c) i Al-3%Si: prone to both micro and macro-segregation due to its wide solidification range which causes dendritic solidification pattern. (Dendrites have a lower alloying element concentration) Al-12.6%Si: prone to normal segregation (macrosegregation) due to planar solidification which drives the lower melting constituent toward the center. ii Al-3%Si: micropores form between dendrites. Al-12.6%Si: may experience gas porosity ( pinholes or larger blowholes ) iii Al-3%Si: dendritic solidification makes free movement of liquid difficult since it increases the apparent viscosity of the mix. Al-12.6%Si: has low apparent viscosity thus better feed iv Al-12.6%Si: planar solidification, low melting point (in dendritic solidification fluid flow is cut off) As freezing range decreases, fluidity increases and viscosity decreases , Freezing range = T L T s T L for 3% Si : freezing range = 627 521 627 = 0.169 for 12.6% Si: freezing range = 521 521 521 = 0 d) The most desirable properties for casting are high fluidity and low viscosity, thus Al (12.6% Si) has better castability. Q2) Solution:...
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- Spring '06