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Advanced High Strength Steels (AHSS) (Quenched & Partitioned (QP)…
Advanced High Strength Steels (AHSS)
Twinning-Induced Plasticity (TWIP)
High Mn TWIP
MIcrostructure
Fully A @ RTP
Modification
Alloying
Mn
Processing
Annealing
Mechanism
Deformation-Induced Twinning
Strain Hardening
Strength & Ductility Combinations
Properties
High Tensile Strength
High Tensile Elongation
Formability
Fracture Resistance
Faulting & Twinning Tendencies
Stacking Fault Energy (SFE)
Factors
Alloying
Al
SFE Increase
Si
SFE Decrease
Range
Low
Promote formation of e-M
High
Limit twins & stacking fault formation
Not Low C Steel
Comparison
TWIP > TRIP: Ductility & Strength
Quenched & Partitioned (QP)
Purpose
Produce ductility-strength combination
Modification
Alloying
Si
Cementite Formation Decreases
M Tempering
Component
C (Diffuse from M) + RA
High C Partitioned A => Strain Induced M
Strain Hardening
Ductility Increases
Processing
2 Step Thermal Treatment
Step 1: Quench below Ms
Produce M + RA
Step 2: Isothermal Holding above Ms
C diffuses from M
Heat Treatments
Austemperting/Martempering: Minimize detrimental residual stresses
Quenching @ above Ms
A => B
Result
Acicular Ferrite Formation
C-enriched A Stabilisation
Austenized & Quenched
Inter critically Austenized