Coarse dendritic cast

Coarse dendritic cast structure with hot cracks (Pb-2.0 wt% Sb alloy) [3]. (a) general view of alloy... 

Figure 18.13 Coarse dendritic cast structure with cracks (lead-2% antimony alloy), (a.b) Industrial grid (x100) (Courtesy of the Swiss Post Office, m)...

Covers for the melt can be used. Prebumed charcoal has been successfully used as a cover and is appHed hot directly from the prebumer. Fluxing and deoxidation is not necessary because of the strong affinity silicon has for oxygen. Silicon-heating scrap must be kept segregated from other scrap, because silicon as an impurity ia other alloys can promote a very coarse dendritic stmcture and weak porous castings. 

Sn-5Sb solder has a near-peritectic composition and a relatively high-liquidus temperature, around 238°C, which is significantly higher than the melting point of eutectic Sn-Pb solder, 183°C. Unlike other alloying elements, the addition of Sb to Sn raises the melting point of Sn gradually as the solid solubility of Sb in Sn increases [49]. The peritectic reaction, which occurs near 246 ° C, produces Sn- Sb microstructures which are complex. A typical cast microstructure of Sn-5Sb alloy solidified rapidly is shown in Fig. 2. This microstructure exhibits coarse dendrites of Sn-rich solid solution with Sn Sb intermetallic compounds dispersed between the dendrites. 

V205-ZnV20e (14.2wt% ZnO) 640 Cast Coarse unbranched dendrites... 

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