A - Austenite
B - Bainite
C - Carbide
F - Ferrite
P - Pearlite
M - Martensite
RA - Retained austenite

CCT - Continuous-cooling transformation diagram
TTT - Time-temperature transformation diagram
TTP - Time-temperature precipitation diagram
TTS - Time-temperature sensitization diagram

A_s - Austenite start temperature
A_f - Austenite finish temperature
A_c1 - Temperature at which austenite begins to form on heating
A_c1b - Temperature at which austenite begins to form on heating
A_ce - Temperature at which transformation of ferrite into austenite is completed upon heating
A_c3 - Temperature at which transformation of ferrite into austenite is completed upon heating
M_s - Martensite start temperature
M_f - Martensite finish temperature
M₅₀ - Temperature of 50% of austenite transformation to martensite
M₉₀ - Temperature of 90% of austenite transformation to martensite

HV - Vickers hardness
HV1 - Vickers hardenss, 1 kg load
HV0.1 - Vickers hardness, 0.1 kg load
HRC - Rockwell hardness

Welding diagrams:

PF - Polygonal ferrite
P - Pearlite
FS(NA) - Ferrite with non-aligned second phase
FSP - Ferrite sideplates
AF - Acicular ferrite
CAF - Coarse acicular ferrite
LF - Lath ferrite
M - Martensite