Scripta Materialia 192 (2021) 115–119 Contents lists available at ScienceDirect Scripta Materialia journal homepage: www.elsevier.com/locate/scriptamat Grain boundary character distribution in an additively manufactured austenitic stainless steel Majid Laleh a,b , Anthony E. Hughes b,c , Mike Y. Tan a,b , Gregory S. Rohrer d , Sophie Primig e , Nima Haghdadi e,∗ a School of Engineering, Deakin University, Waurn Ponds, VIC 3216, Australia b Institute for Frontier Materials, Deakin University, Waurn Ponds, VIC 3216, Australia c Commonwealth Scientific and Industrial Research Organisation (CSIRO), Mineral Resources, Private Bag 10, Clayton South, VIC 3169, Australia d Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA e School of Materials Science & Engineering, UNSW Sydney, Sydney, NSW 2052, Australia a r t i c l e i n f o Article history: Received 1 September 2020 Revised 7 October 2020 Accepted 9 October 2020 Keywords: Grain boundary engineering Additive manufacturing Austenitic stainless steel a b s t r a c t The grain boundary character distribution (GBCD) in an austenitic stainless steel produced by additive manufacturing (AM) in both as-built and annealed conditions was studied. Relatively fine grains and a non-fibre texture was achieved by AM, and as-built structure showed a high population of 3 bound- aries. A five-parameter GBCD analysis revealed that the microstructure is mostly dominated by highly incoherent 3 boundaries. The grain boundary network also consisted of random high angle, coherent 3s terminating on (111) planes with a pure twist character, and tilt 9 boundaries. The findings show prospects for the possibility of engineering the grain boundary network of materials in-situ, via the stress and heat induced by the thermal cycles during AM. © 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology that uses a high-energy laser beam to melt pow- der particles to consolidate a metallic part [1,2]. Upon laser ir- radiation of a powder bed, a melt pool forms and then solidi- fies at a very fast rate (up to 10 7 K/s [3]). Individual tracks join together during succeeding laser passes to form a 3D part. Dur- ing LPBF, the material experiences complex thermal gradients and gyrations which subsequently result in a unique microstructure. These unique microstructural features can lead to superior me- chanical properties [4,5] and corrosion resistance [6–8] e.g. in LPBF austenitic stainless steels, exceeding those of their traditionally manufactured counterparts. A current focus in the metal AM re- search community is directed towards understanding such complex microstructures in order to develop metals and alloys with opti- mised properties of interest by altering processing variables [9]. Grain boundary engineering (GBE) has been the subject of in- tensive research during the last 40 years with the aim of intro- ducing coincident site lattice (CSL) and low-angle grain boundaries (GBs) to mitigate undesirable intergranular phenomena such as corrosion, embrittlement and fracture [10–14]. While GBE has been studied for traditionally manufactured stainless steels, the poten- ∗ Corresponding author. E-mail address: nima.haghdadi@unsw.edu.au (N. Haghdadi). tial of the thermomechanical hysteresis that a material experiences during AM for engineering microstructures is yet to be explored. Typical anisotropic microstructures reported in AM materials con- sisted of grains elongated towards the build direction with <100> and/or <110> texture [15,16]. Such morphology can be broken down via a change in laser scanning strategy, where a hierarchi- cal microstructure can be formed that offers outstanding mechani- cal properties achieved either through microsegregation resulting from cellular solidification and/or via a network of dislocation- rich sub-boundaries [4,17]. It can be hypothesized that engineer- ing the grain boundary network in austenitic stainless steel via AM may unlock additional unique properties in terms of corrosion, embrittlement and fracture resistance. This is because diffusivity, mobility, and segregation of a grain boundary are affected by its crystallography. However, an analysis of the formation mechanism and a detailed knowledge of the crystallographic character of CSL grain boundaries in AM microstructures is currently lacking. The current work reports on the possibility of in-situ GBE during AM of an austenitic stainless steel, and provides a full five-parameter macroscopic description of these boundaries. The results can be ex- tended to several other face centred cubic (FCC) metals with low- to-medium stacking fault energy (SFE). Argon-atomised 316L austenitic stainless steel (hereinafter 316L SS) powder with particle sizes between 5 and 45 μm was used. Cubes (10 × 10 × 10 mm 3 ) were produced using a LPBF machine https://doi.org/10.1016/j.scriptamat.2020.10.018 1359-6462/© 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.