Size effect on compressive strength and deformation of additively manufactured 316L stainless steel micropillars

Abstract

The properties of additively manufactured (AM) 316L stainless steel (SS) have been investigated in compression using single crystal micropillars with diameters ranging from 800 to 4000 nm. The AM 316L SS sample was fabricated by selective laser melting (SLM) and subsequently heat treated at 950 degrees C for 2 h followed by air cooling, to relieve residual stress. Micropillars were fabricated from grains of pre-selected orientation using gallium focused ion beam (Ga-FIB) in a helium ion microscope (HIM), enabling the determination of resolved shear stress (RSS) on [111] glide planes. The heat-treated AM 316L SS pillars exhibit a strong size effect with (RSS) increasing as the pillar size decreases, following a power-law relation with an exponent of-0.69. Deformation primarily occurred through the activation of the {111}<101> slip system, as evidenced by sharply defined slip planes and multiple parallel slip bands observed post-compression. The size effect was compared with literature values for the austenite phase in dual-phase and austenitic stainless steels as well as pure Ni samples, which serve as references for single-element face-centered cubic (fcc) metals. This size exponent aligns closely with the empirical trend observed in fcc metals, suggesting that even after processing induced microstructural evolution, AM 316L SS retains the universal size dependent strengthening behavior characteristic of fcc materials. These findings emphasize the effect of additive manufacturing and subsequent thermal processing on microscale mechanical properties.