Influence of Nonmartensitic Transformation Products on Mechanical Properties of Tempered Martensite

Abstract : The influence of nonmartensitic transformation products on the mechanical properties of tempered martensite is presented for samples of an SAE 4340 steel, partially isothermally transformed to specific high-temperature transformation products and quenched and tempered to hardness values of from 25 to 40 Rockwell C. The effects of upper bainite in amounts of 1, 5, 10, 20, and 50 percent, of 5 percent ferrite, and of 5 percent pearlite on the tensile, impact, and fatigue properties are evaluated.