5. The MgO-Al2O3 phasediagram is quite prevalent in the refractory, cement and glass industries. The phasediagram shows

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5 The Mgo Al2o3 Phasediagram Is Quite Prevalent In The Refractory Cement And Glass Industries The Phasediagram Shows 1 (343.94 KiB) Viewed 27 times

5. The MgO-Al2O3 phasediagram is quite prevalent in the refractory, cement and glass industries. The phasediagram shows the stable region of the so-called "spinel phase" (MgAl2O.). This phase has a high melting point, a high resistance to chemical degradation and a high mechanical strength at high temperatures. a. What are the compositions and weight fractions of the stable spinel phase at 1600 °C for an alloy consisting of 40 wt% Al2O3? b. What if the mixture consists of 90 wt% Al2O3? Composition (mol% A1,03) 20 40 60 80 2800 Liquid 5000 ALO 4500 2400 MgO (ss) MgAI 04 (ss) + Liquid + + Liquid Liquid 4000 Temperature (C) Mgo (ss) 2000 Temperature (°F) 3500 MgA1204 (ss) 3000 1600 Mgo (ss) MgA1,04 (ss) MgAl04 (ss) 2500 A1,03 1200 2000 20 80 0 (Mgo) 40 60 Composition (wt% Al03) 100 (Al2O3) Mgo = = MgAl204 0,7; 9Mgo a. 9A1203 = 0,035; 9A1203 0,4511; 9MgA1204 = 0,5489 AL;O; = 1; 9Mgal,0, = 0,5; 9A1,0, = 0,5 MgAl2O4 = 0,8; 9 AL203 b. 9 Al,03