(a) An Al-Si alloy phase diagram is shown in Figure Q2. The eutectic point is at...

Transcribed Image Text:

(a) An Al-Si alloy phase diagram is shown in Figure Q2. The eutectic point is at 12.6wt%Si and the maximum solubility of Si in Al matrix is 1.65%. Note that the melting temperature of the pure Al is 660 °C. For Al-1% Si, Al-5%Si, Al-12.6%Si and Al-20%Si alloy systems; (i)describe the solidification path when the melt is cooled from 1000 °C to room temperature (ii) provide schematic illustration of their microstructures at room temperature (iii) indicate the volume fraction of primary and eutectic phases at room temperature 1500 (b) Gravity die casting (GDC), sand casting (SC), low pressure die casting (LPDC) and high pressure die casting (HPDC) processes are widely used for automotive aluminium alloy castings. However, for automotive wheels only low- pressure die casting process is used. Discuss why HPDC, GDC and SC processes are not preferable and give key reasons for selecting LPDC process. Temperature (°C) 1000 500 Al a + L 1.65 12.6 20 L 40 577 x + ß 60 B+L Weight percent silicon 80 99.83 B Si (a) An Al-Si alloy phase diagram is shown in Figure Q2. The eutectic point is at 12.6wt%Si and the maximum solubility of Si in Al matrix is 1.65%. Note that the melting temperature of the pure Al is 660 °C. For Al-1% Si, Al-5%Si, Al-12.6%Si and Al-20%Si alloy systems; (i)describe the solidification path when the melt is cooled from 1000 °C to room temperature (ii) provide schematic illustration of their microstructures at room temperature (iii) indicate the volume fraction of primary and eutectic phases at room temperature 1500 (b) Gravity die casting (GDC), sand casting (SC), low pressure die casting (LPDC) and high pressure die casting (HPDC) processes are widely used for automotive aluminium alloy castings. However, for automotive wheels only low- pressure die casting process is used. Discuss why HPDC, GDC and SC processes are not preferable and give key reasons for selecting LPDC process. Temperature (°C) 1000 500 Al a + L 1.65 12.6 20 L 40 577 x + ß 60 B+L Weight percent silicon 80 99.83 B Si

Answer rating: 100% (QA)

a i Solidification Path Al1Si alloy The alloy will solidify as a singlephase solid solution of aluminum with dispersed silicon atoms Al5Si alloy Upon cooling primary silicon will start to form first f... View the full answer