Etch-Pit Observations Concerning Twins in Iron and Iron Alloys

Etch-pit procedures may be used to gain qualitative information about processes involving twins in samples deformed to strains of the order of 10%; a visual representation of the local strain fields may be obtained together with evidence which may be interpreted in favor of the emissary dislocation model for twin growth. The etch-pit procedure reveals about 10% of the dislocations thought to be present and indicates local stresses around twin/twin or twin/grain boundary intersections at least 20% higher than the over-all stresses at distances of about 10 μ or five times the width of the twins.