GRADED INTERFACE CALCULATOR

Cold-Weld Fracture Prevention | Diffusion Zone Thickness Computation
Context

When dissimilar alloys meet at a weld or braze interface, thermal expansion mismatch creates shear stress at the junction. Below a critical interface thickness, the bond fails catastrophically via cold-weld fracture. Above it, the graded zone absorbs strain through controlled dislocation motion.

Target: Compute the minimum diffusion zone thickness that prevents fracture under operational thermal cycling.

Material Properties
Governing Equation:

δ_crit = (k × ΔT × |α₁ − α₂|) / τ_y

Annealing Ramp: dT/dt = k / (α_avg × δ_crit)

Where:
• δ_crit = minimum diffusion zone thickness (meters)
• k = effective thermal conductivity (W/m·K)
• ΔT = operational temperature range (Kelvin)
• α = linear thermal expansion coefficient (1/Kelvin)
• τ_y = shear yield strength of weakest phase (Pascals)
Grounding: This formulation derives from the Griffith-Orowan criterion for interfacial fracture, adapted for graded metallurgical transitions.
Source: Q1144771 (Griffith theory) × NBS Monograph 25: Weld Metallurgy
Cross-reference: SCRAP-2026-0412 — 11% threshold validation via cold-weld simulation.