Controlling microstructure and mechanical properties of additively manufactured high-strength steels by tailored solidification

Abstract

The development of novel alloys specifically designed for additive manufacturing (AM) is a key factor in using the full potential of AM. This study addresses the design of advanced high strength steels (AHSS) that take advantage of the processing conditions during AM by laser powder bed fusion (LPBF). The alloy screening was guided by computational alloy selection (combined CALPHAD, Scheil-Gulliver, and phase-field simulations) and by rapid processing using powder blends (X30Mn21 steel and Al). Increasing Al contents, ranging from 0 to 5.4 wt. %, promoted bcc-fcc solidification, and allowed for tailoring the stacking fault energy (SFE). On the one hand, the transition from fcc to bcc-fcc solidification enabled controlling the microstructure and texture evolution during AM. On the other hand, the wide SFE range between 8 J/m² (0 wt. % Al) and 44 J/m² (5.4 wt. % Al) promoted flexible adjustment of the active deformation mechanisms, including transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), to govern the work-hardening behavior. The microstructure after LPBF and after plastic deformation was analyzed by XRD, SEM, EDX, EBSD, EPMA, and TEM. Mechanical properties of bulk specimens and lattice structures were analyzed using tensile and compression testing with a focus on energy absorption capacity. The influence of the chemical composition and the solidification conditions during LPBF on the microstructure evolution and the related microstructure-property-relationships of bulk and lattice structure specimens will be discussed.

Electrochemical impedance spectroscopy study of the passive film for laser-beam-melted 17-4PH stainless steel

“…Indeed, these new pro cesses allow the fabrication of near-net-shaped structures of many metallic materials without prohibitive waste generation and with sub stantial tin1e saving [1]. Additively manufactured (AM) steels have been largely studied, and abundant literature has been focused on the mi crostructures of AM steel components, and only a few ve1y recent ref erences have been given here [2][3][4]. However, ve1y few papers concemed their corrosion properties, and the largest part of these con cemed 316 L stainless steel (SS) [5][6][7][8][9][10][11][12].…”

Design Aspects of Additive Manufacturing at Microscale: A Review

“…Recent advancements in the field of design, modeling and simulation, fabrication, and testing of lattice structures can be found in the following review papers [ 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 ]. Deriving the effective properties of additively manufactured micro-lattice structures is an important tool in the hands of designers for performing fast simulations at a low computational cost [ 126 , 137 , 138 , 139 ]. Souza et al [ 139 ] derived a closed-form analytical solution of lattice structures fabricated by selective laser melting, using beam models.…”

Electron Beam Powder Bed Fusion of Water Atomized Iron and Powder Blends

“…While segregation tendency was noted, this led to a reduction of crack density. Köhnen et al employed powder blends for fast alloy screening in PBF-LB manufactured steel [12]. The same approach was taken in the experimental development of high-entropy alloys [13].…”