Materials Test 2 phase terms

Binghamton University ME362 exam 2

Eutectic transformation

L —> S₁ + S₂

Eutectoid transformation

S₁ —> S₂ + S₃

Peritectic transformation

L + S₁ —> S₂

Austenite (𝛾) solid phase

• ‘Parent’ phase of steel

• FCC

• Ductile, non-magnetic

Ferrite (α) solid phase

• Stable phase of iron at room temp

• Can only hold tiny amount of carbon (< .022 wt%C)

• BCC

• Soft, ductile, magnetic

Cementite (Fe₃C) solid phase

• A chemical compound of iron and carbon with a FIXED COMPOSITION of 6.70 wt%C

• Very hard, very brittle

Pearlite (P) microconstiuent

• Alternating layers of Ferrite (α) and Cementite (Fe₃C)

• Forms from the eutectoid reaction

• Decently strong and ductile

Banite (B) microconstituent

• Needles/feathers of Ferrite (α) and Cementite (Fe₃C)

• Forms from cooling Austenite on TTT diagram

• Harder and stronger than Pearlite

Martensite (M), metastable phase

• Metastable phase, so not on the equillibrium Fe-C diagram

• Formed from quenching Austenite (carob atoms get trapped)

• Stretched BCC

• Extremely hard, very brittle

• Hardened steel is hard because of this.