quiz5fall01 - rL ENSC 3313, Fall 2001 Answer any 4...

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rL Name ENSC 3313, Fall 2001 QuizS Answer any 4 Questions only, 1 point each The starting material is a 10 rnrn diameter yellow brass (70 Cu -30 Zn) rod of hardness HRB (RB) ~. Required is an ~ diameter rod ofHRB 1Q. Describe an apRroRriate processing sequence. HRB = 70 signifies final processing stage of 20% cold work. Hence, we will need a' do ' given by 0.20 = ~ ~ ~ ~- .@ ~ = d2 o do = 8.94 mm O.8d~ =64, The material is heavily cold worked initially, hence we must soften (anneal) the rod. Thence, hQ! work from 10 mrn diameter to 8.94 mrn diameter, thence cold work 20% 2!: anneal thence cold work to 8.94 mrn diameter, anneal thence cold work 20%. If a particular cold worked brass rod takes 60' to recrystallize at 450°C and 20' to recrystallize at 480°C, then how long should recrystallization take at 500°C? 2 Recrystallization is a diffusion-controlled process. Rate = ! = Ce-B/T t where B, C are constants -B( 1h-1h ) = Ce-B/723 Dividing, Substituting, 3=e 1 60 1 20 = Ce-B/7S3 B = 19,936
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quiz5fall01 - rL ENSC 3313, Fall 2001 Answer any 4...

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