A novel mechanism to generate metallic single crystals

Abstract

Generally, the evolution of metallic single crystals is based on crystal growth. The single crystal is either produced by growing a seed single crystal or by sophisticated grain selection processes followed by crystal growth. Here, we describe for the first time a fully new mechanism to generate single crystals based on thermo-mechanically induced texture formation during additive manufacturing. The single crystal develops due to two different mechanisms. The first step is a standard grain selection process due to directional solidification, leading to a pronounced fiber texture. The second and new mechanism bases on successive thermo-mechanically induced plastic deformations and texture formation in FCC crystals under compression. During this second step, the columnar grain structure transforms into a single crystal by rotation of individual grains. Thus, the single crystal forms step by step by merging the originally columnar grain structure. This novel, stress induced mechanism opens up completely new perspectives to fabricate single crystalline components and to accurately adjust the orientation according to the load.

Dynamic Crystal rocking of Nickel-Based Single Crystal Superalloy during the Epitaxial Growth of the Additive Manufacturing Process

“…As illustrated in Supplementary Movie 1, all lattice planes rotate in the same direction, but show subtly different rotation angle, indicating the existence of both the rigid-body rotation and the rotation of lattice planes induced by the deformation. Apparent crystal rotation can be found relative to the initial substrate, which was also found by other researchers [34,35].…”

Combined Effects of Concentration, pH, and Polycrystalline Copper Surfaces on Electrocatalytic Nitrate-to-Ammonia Activity and Selectivity

“…While the effects of polycrystalline Cu on CO 2 reduction have been well characterized, this is not the case for NO 3 – reduction. Quantifying performance of polycrystalline surfaces is important to consider as large-scale manufacturing techniques including electrodeposition and additive manufacturing will likely result in polycrystalline microstructures for the electrode . Therefore, this study focuses on quantifying effects of pH and NO 3 – concentration on a polycrystalline Cu surface, which has not been considered as much as controlled surfaces such as Cu(111) and Cu(100).…”

Effect of scan strategy on the formation of a pure nickel single-crystal structure using a flat-top laser beam via laser powder bed fusion

“…Furthermore, the uniform heat-intensity in the flat-top profile has yielded promising results in achieving homogeneous textures [ 3 , 9 , 10 ] and single crystal (SX) structures [ 11 ]. The uniform heat intensity distribution in the flat-top laser resembles the heat distribution of an electron beam in an electron beam powder bed fusion (EPBF) process, which has been studied to cause a <001> ║BD texture and an SX structure [ 12–15 ]. However, the fabrication of an SX structure by LPBF using the typical Gaussian profile is challenging because of the focused heat intensity at the center of the beam area [ 16 ].…”

“…To date, the grain-selection process for the <001> fcc growth in the SD and HD axes, as well as the formation of <011>║SD and HD textures in the EPBF-derived SX structures, has not been clearly understood, as plainly stated in [ 13–15 ]. Pistor et al [ 12 ] proposed that the <011>║SD and HD textures in the EPBF-derived SX structure were induced by the {111} <110> fcc slips during the plastic tension – compression deformation. However, the proposed theory in [ 12 ] contradicts the result in [ 11 ], as the LPBF-derived SX structure does not display significant plastic deformation, which is indicated by the suppressed strain accumulation and low dislocation density.…”

“…Pistor et al [ 12 ] proposed that the <011>║SD and HD textures in the EPBF-derived SX structure were induced by the {111} <110> fcc slips during the plastic tension – compression deformation. However, the proposed theory in [ 12 ] contradicts the result in [ 11 ], as the LPBF-derived SX structure does not display significant plastic deformation, which is indicated by the suppressed strain accumulation and low dislocation density. Thus far, the comprehension of the flat-top-LPBF-derived SX structure formation is limited to controlling the melt-pool geometry to realize the <001> fcc growth in the direction ║BD [ 11 ].…”