Knowledge Base

Fundamentals

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GR
Fundamentals

Grain Boundaries — Types, Energy, Segregation and Engineering Significance

Complete guide to grain boundaries in metals. Covers low-angle tilt/twist boundaries, high-angle boundaries, CSL boundaries, grain boundary energy, solute segregation (P, S, B, H), Hall-Petch equation, and grain refinement.

TH
Fundamentals

The Eutectoid Reaction in Steel — Austenite to Pearlite at 0.77%C, 727°C

Complete guide to the eutectoid reaction in steel (γ → α + Fe₃C at 0.77%C, 727°C). Covers cooperative ferrite-cementite growth, lamellar spacing, Avrami kinetics, colony formation, and the relationship to hypo- and hypereutectoid steels.

WI
Fundamentals

Widmanstätten Structure — Formation in Steel HAZ and Effect on Toughness

Guide to Widmanstätten ferrite in steel. Covers formation mechanism at moderate undercooling, HAZ appearance in welds, crystallographic orientation relationship with austenite, and detrimental effect on Charpy impact toughness.

AC
Fundamentals

Acicular Ferrite — Nucleation at Inclusions and Toughness in Weld Metal

Complete guide to acicular ferrite in steel weld metal. Covers intragranular nucleation at oxide/sulfide inclusions, interlocking needle morphology, CVN toughness compared to other weld microstructures, and inclusion chemistry requirements.

DE
Fundamentals

Delta Ferrite in Stainless Steel Welds — WRC-1992 Diagram and Ferrite Number

Technical guide to delta ferrite in austenitic stainless steel welds. Covers WRC-1992 Schaeffler diagram, Ferrite Number (FN), 3–8 FN optimal range for hot cracking prevention, sigma phase risk, and composition control.

PE
Fundamentals

Pearlite Microstructure — Lamellar Ferrite-Cementite in Eutectoid Steel

Complete guide to pearlite microstructure in steel. Covers eutectoid reaction at 727°C, lamellar interlamellar spacing vs temperature, hardness, applications in rails and high-strength wire, and fine vs coarse pearlite.

MA
Fundamentals

Martensite in Steel — Diffusionless Transformation, BCT Structure and Hardness

Complete guide to martensite in steel. Covers diffusionless FCC→BCT transformation, Koistinen-Marburger equation, carbon content vs hardness relationship, lath vs plate morphology, and why tempering is essential.

BA
Fundamentals

Bainite — Upper and Lower Bainite Formation in Steel

Complete guide to bainite microstructure in steel. Covers upper bainite (350–550°C), lower bainite (250–350°C), formation mechanism, bainite vs tempered martensite toughness comparison, and industrial applications.

RE
Fundamentals

Retained Austenite in Steel — Causes, Measurement and Sub-Zero Treatment

Technical guide to retained austenite in hardened steels. Covers formation mechanism, effect of carbon content on fraction retained, problems in bearings and tool steels, XRD measurement, and sub-zero cryogenic treatment.

SL
Fundamentals

Slip Systems in Metals — BCC, FCC and HCP Compared

Technical guide to slip systems in BCC, FCC, and HCP metals. Covers slip planes and directions, Schmid factor, critical resolved shear stress (CRSS), Von Mises criterion for polycrystalline ductility, and why FCC metals are most ductile.