Question

1. Circle whether the following statements are true (T) or false (F). (2 mark each, total: 32) I F Substitutional atoms replace the solvent atoms in a unit cell F F Increasing grain size will increase the yield strength. F Growth of a phase is a thermally activated process. T F Spheroidizing results in coarse precipitates. TF Hot working requires less energy for plastic deformation than cold working F F A eutectoid reaction can be written as: Le Solid 1 + Solid 2. F Martensite is a phase with needle-shaped grains. F The oxidation reaction occurs at the anode. F The tendency to form pearlite at slow cooling rates (< 35 °C/s) makes welding AISI 1080 steel difficult. IF Fast cooling rates for an alloy with high hardenability will produce small amounts of martensite. TF Annealing can reverse the effects of strain hardening. TF The development of microstructures can be predicted by a phase diagram under Non-equilibrium conditions. TF The lamellar eutectic structure confines dislocations and impedes their motion. TF Two solid phases and a liquid phase coexist in equilibrium at the eutectic point. F F Substitutional diffusion occurs via vacancy-atom exchange. TF All Fe-C transformation diagrams (TTT and CCT) assume starting from Austenite.

Answer 1

O-Selutions i Subsitutional atoms replace the soluent atoms in a unit cell? True (the substitutional alors replace parents atoms and take their place ). Il increasing grain size will increase yield strength? false , ( Because as they grain size increases the . Strength decreases ). li, Growth of phase is a thermally activated process? True (sue to the heat and mass transport Thermaly activated the process introduces the growth of phose ☺ Spheroidizing results in coarse precipitates : True (Here it is amethod of prodonged heating at temperature below the eutectoid temperature , results in Coarse precipitates. V Hot working requires less energy for plastic deformation than cold working True: (Due to the availability of higher amount g kinetic Energy deformation is easier,

vi False (the written Eutectoid reaction can be as Lax solid 1 of Solid 3)

v Martensite is a phase with header shaped gains, True ( Martensite was originally named for a very hard A very britte phose g stal that has needle shaped) - vill The onidation Reaction occurs at anode True C The Guidation take place at anode and A seduction at Cathode) True (the reason is to form peastite at slow cooling rates makes welding AISI 1080 steel difficult because at the slower cooling sote Pearlite will be formed an ein peoslite the Carbon content is low , so it weakens the weld Strength false Calloy with high hardenability will produce small amount of martengite even at slow cooling erate. High hardenability refers to the ability to form harden in depth,

Ex True Can reverse the effects of strain Cannealing herdening) shi True ( They are predicted under Earuitlibrium conditions) (the lamellar eutectic structure confines dislocations and impedes their motion), ( one liquid transforms into two) xn, True e Tome (substitutional diffusion occurs via Vacancy atom Exchange) Xian false (No not all fere transformation diagrama assume Starting from Austenite,