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MATSE 427 Exam 2 Questions And Answers
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MATSE 427 Exam 2 Questions And Answers
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Solution 2024/2025Pepper
MATSE 427 Exam 2 Questions And Answers
Hardness in Martensite is caused by (1) ANS✔✔ Supersaturation of C in atoms in BCT which induce large strains
Hardness in Martensite caused by (2) ANS✔✔ High dislocation density in lath M and twin density in plate M
Hardness in Martensite caused by (3) ANS✔✔ Hardness increases with increasing C content but levels off and partially
declines after 0.8 wt% C due to retained austenite
Define hardenability ANS✔✔ Ability of a steel to form M
D_0 in J-Test ANS✔✔ actual bar diameter
D_i in J-Test ANS✔✔ ideal bar diameter
Steps to find D_0 ANS✔✔ 1) Determine Hardness of 50% M for samples wt% C - given in tables
2) Use J-Distance to find D_i from table
3) Use graphs of D_i vs D_0 to read curve with given quench criteria to find D_0
What Effects Quench ANS✔✔ Quenching Media and Agitation Amount
Wt% C effect on hardenability ANS✔✔ increasing C increases hardenability
Alloying Content effect on hardenability ANS✔✔ Increasing alloying content increases hardenability
Austenite Grain Size effect on hardenability ANS✔✔ Increasing austenite grain size increases hardenability (NEVER
DONE IN REAL LIFE)
, Solution 2024/2025
Pepper
Quench effect on hardenability ANS✔✔ Increasing Quench severity increases hardenability
Bar size effect on hardenability ANS✔✔ Decreasing bar size increases hardenability
Equation to calculate D_i from Grossman multiplying factors ANS✔✔ D_i = (base D_i)(Alloying Multiply Factor) [factors
given in tables]
Why Temper (general) ANS✔✔ increase ductility and toughness, decrease strength and hardness
Supersaturation of C atoms in BCT cause strain, DF for ANS✔✔ carbide formation during tempering
High interfacial energy associated with high density of lath and plate boundaries, DF for ANS✔✔ grain growth and
coarsening during tempering
High strain energy associated with high dislocation and twinning density, DF for ANS✔✔ recovery during tempering
Retained Austenite, DF for ANS✔✔ austenite transformation to ferrite and cementite during tempering
Stage 1 Temper Temp Range ANS✔✔ 40C to 200 C
[40-100C] Microstructure change during Tempering ANS✔✔ C diffusion to octahedral and dislocation sites
[100-200C] Microstructure change during Tempering ANS✔✔ Formation of transition carbides
Transition Carbides formed during stage 1 of temper ANS✔✔ n-carbide = Fe2C
E-carbide = Fe2.4C
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