Effect of Alloying Elements on the Mechanical Properties of the Stable Austenitic Stainless Steel

Abstract

The effects of various alloying elements on the mechanical properties of stable austenitic stainless steel have been investigated in order to soften it. Results obtained are as follows: (1) Experimental equations are proposed, which give the hardness (HV), 0.2% proof stress (σ02) and tensile strength (σB) as functions of the chemical composition. (2) Reduction of C, N, Si, Cr and Mo and addition of Ni, Cu and Mn are effective to decrease the hardness, 0.2% proof stress and tensile strength. (3) σ0 2 is increased by the addition of alloying elements which cause lattice strains, i.e., C, N and Mo. The larger the lattice strain, the larger the increase in σ02. 0.2% proof stress is decreased by the addition of Ni, Cu and Mn, which increase the stacking fault energy (SFE), although these elements cause slight lattice strains. Addition of Si, which reduces SFE, increases σ0.2. (4) The dislocation structures are essentially cell-structures, except for N-added steels. The cell size is varied with alloying elements through the change in SFE. (5) The work hardening rate is reduced by Ni, Cu and Mn, which have been reported to increase SFE and hence are considered to activate cross-slip. On the other hand, a SFE-reducing element, Si, increases the work hardening rate. The addition of N, another SFE-reducing element, however, decreases work hardening rate. This effect may result from the difficulty in forming the cell-structure in the N-added steel in contrast with the Si-added steel. © 1994, The Iron and Steel Institute of Japan. All rights reserved.