As-processed Condition Research Articles

Synergistic enhancement of strength and ductility in novel solid-stir continuous extrusion: Influence of heterogeneous microstructure and alloy chemistry

Friction stir-derived solid-state processes leverage the synergistic effect of frictional heating and intense shear deformation to achieve localized microstructural modification for the improvement of mechanical properties. In the present work, a novel processing route called solid-stir extrusion (SSE) has been explored for continuous, high-rate extrusion of a high strength non-age-hardenable-AlMgSc alloy. In the current study, loss of strength associated with frictional heating during the process is mitigated as elevated strength is observed in as-extruded condition, thereby eliminating the need for post process heat treatment. The effect of process attributes on mechanical property and microstructure evolution was investigated. The SSE process caused extensive grain refinement and fragmentation of thermally stable Al3Sc intermetallic periodically at shear bands, which contributes to the elevated mechanical strength. The spatial variation in mechanical properties and microstructural heterogeneity was characterized using nanoindentation and microstructural correlation. The current findings indicate the significance of the process-specific alloy design approach to increase performance of material in as-processed condition.

Recrystallization and grain growth in single tungsten fiber-reinforced tungsten composites

High heat fluxes in future fusion reactors pose big challenges on the materials of plasma-facing components due to restoration processes occurring at high temperatures. Tungsten is considered most suitable as plasma-facing material. To overcome its inherent brittleness at low temperatures, tungsten fiber-reinforced tungsten composites are developed which contain ductile, potassium-doped, drawn tungsten wires in an undeformed tungsten matrix. Such composites show pseudo-ductile behavior, an improved toughness and a more controlled fracture compared to undeformed tungsten. Model systems containing a single fiber either without any interlayer or with an yttria interlayer between fiber and matrix are annealed and characterized by electron backscatter diffraction (EBSD) in order to investigate their thermal stability. The restoration process in wire and matrix differ from each other: Recrystallization followed by grain growth occurs in the deformation structure of the wire. Grain growth is the sole mechanism affecting the undeformed matrix. An yttria interlayer between fiber and matrix is supposed to separate the differently restoring microstructures from each other and thereby preserve the improved mechanical properties of the composite. The investigation focuses on characterizing the as-processed condition and the microstructural changes after annealing at 1450 °C for either four days or two weeks. After two weeks of annealing, grains in the region or the vicinity of the wire have coarsened so much that former fiber and matrix cannot be distinguished any longer; not even in a model composite with a 1 μm thick yttria interlayer.

Investigating microstructural evolution in SolidStir™ extruded oxide dispersion strengthened 14YWT alloy fuel cladding tube

Structural components for extreme environments require advanced materials and manufacturing processes. One such advanced material is oxide dispersion strengthened (ODS) Fe–14 wt.%Cr–3W–0.4Ti–0.3Y2O3 (14YWT), which is developed for components to be used in Gen IV and fusion nuclear reactors. However, the conventional manufacturing processes to produce components, such as fuel cladding tubes, either do not retain the desired microstructural attributes or are costly and less efficient. As a result, a more attractive option is a novel manufacturing process developed on the principle of friction stir welding or processing (FSW/P) and commercially referred to as SolidStir™ Extrusion (SSE). This study used the SSE technique to study the manufacturing and microstructural evolution of a fuel cladding tube made of ODS 14YWT alloy. The cladding extrusion by the SSE technique involved the use of ball-milled 14YWT powders with Y, Ti, and O in the solid solution and the use of a specially designed W-25Re-Hf tool for consolidation and extrusion of the powders. A scanning electron microscope (SEM), electron backscattered diffraction (EBSD), and transmission electron microscope (TEM) were utilized for microstructural characterization. A Keyence microscope captured macrostructural photographs of the extruded tube. EBSD examination of the extruded tube on both transverse and longitudinal cross-sections showed the presence of dynamically recrystallized grains and revealed that the average grain size of the transverse cross-section was smaller than that of the longitudinal cross-section. The texture was weak and consisted of some amount of shear texture. The presence of nano-oxide clusters or precipitates of Y, Ti, and O (pyrochlores) in the extruded tube was determined by TEM. Aging heat treatment caused the average precipitate size to decrease and the density to increase compared to the as-processed condition. The results indicated that SSE is a viable tool for manufacturing fuel cladding tubes with the desired microstructural attributes.

Structural and superelastic properties of Fe–Mn–Al–Ni shape memory alloy sheets produced on industrial process routes by hot rolling

In the present study the structural and functional properties of Fe–Mn–Al–Ni shape memory alloy sheets produced on an industrial process route focusing on hot rolling were investigated. The as-processed condition is characterized by a high fraction of the non-transforming γ-phase, which ensures good workability, but is associated with poor superelasticity. The alloy shows good structural properties with a yield strength of about 600 MPa, which is well above the usual transformation stress related to the martensitic phase transformation for the investigated alloy composition. After solution annealing, a microstructure showing no preferred orientation being characterized by distinctly larger grains is present. The results obtained reveal that the previous thermo-mechanical processing had no impact on the subsequent texture, however, provided a sufficient amount of driving force for abnormal grain growth. Imposed by a cyclic heat treatment, oligocrystalline structures with grain sizes above 10 mm can be achieved in the industrially processed material, which show superelastic properties similar to material processed in small batches in the laboratory.

Additive manufacturing of functionally graded inconel 718: Effect of heat treatment and building orientation on microstructure and fatigue behaviour

This paper addresses the effect of the post-process heat treatments on the microstructure and fatigue crack growth behaviour of the functionally graded (FG) laser powder bed fusion (L-PBF) Inconel 718 (IN718) superalloy. Sets of samples were additively manufactured (AM) altering the process parameters, namely the laser power, the laser scanning speed, layer thickness, hatch distance, and beam distribution function, resulting in distinctly different microstructures. Two categories of samples underwent heat treatment (HT) and hot isostatic pressing followed by HT (HIP+HT), while one category was kept in the as-processed (AP) condition to reveal the effects of the post-treatments. Additionally, to study the effect of microstructural anisotropy, samples were printed in horizontal (H) and vertical (V) building directions. To better understand the behaviour of the FG materials, non-graded (NG) L-PBF samples and wrought material were investigated as references. Significant variations in terms of porosity, grain size and elongation, crystallographic texture, and content of the strengthening precipitates or detrimental phases were found in different AM groups. The fatigue behaviour of the NG and FG materials was also studied by conducting three-point bending tests. Findings in terms of the role of different microstructures on the fatigue-crack initiation and fatigue crack growth rate are presented and discussed for all samples. The study demonstrated that heat treatments can enhance the damage tolerance of L-PBF IN718 to the level of wrought material. Interestingly, the effect of the roughness induced crack closure was found to be a function of build orientation, especially in the low stress ratio regime.

Material-property correlations for a high-alloy special steel

Abstract Using the example of the high-alloy austenitic steel 1.4828 (X15CrNiSi20-12), which is typically used for high-temperature applications, this paper will demonstrate how the performance characteristics of semi-finished products are impacted by the condition of a material after production and processing. For this purpose, samples of a cost-effective as-cast condition and a comparatively expensive as-forged condition were studied in a comparative approach. The microstructure was examined by means of light optical as well as scanning electron microscopy, hardness values were determined, and the corrosion behavior was characterized by electrochemical investigations. The comparative studies show that despite an almost identical chemical composition, both the as-fabricated and as-processed conditions of a material have a decisive impact on the performance characteristics, particularly on corrosion behavior.

Artificial silicide barrier coatings in titanium matrix composites

Abstract A continuous S2 silicide ([Ti,Zr] x Si y ) segregation layer was found in the fibre matrix interface of SCS6-SiC/Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si (IMI834) composites (composition in wt.%). The S2 layer separates completely the titanium matrix from the reaction layer. It was shown that the S2 layer stabilises the interface during thermal treatment. The thermal stability of composites was tested in which artificial coatings were introduced into the interface. For the artificial coatings a composition and structure of the S2 silicides were aspired. The interface of the composites was investigated with analytical transmission electron microscope in the as-processed condition and annealed at 700 °C for 3 000 h and at 800 °C for 1000 h. The coatings of the same composition and structure can be introduced into the interface of SiC-SCS6/IMI834 composites as those of the S2 silicide obtained by self-segregation. The composites with the artificial coatings have a similar interface stability at 700 °C as those obtained by self-segregation.

Omega versus alpha precipitation mediated by process parameters in additively manufactured high strength Ti–1Al–8V–5Fe alloy and its impact on mechanical properties

The high strength metastable β-Ti alloy, Ti–1Al–8V–5Fe (wt%), also referred to as Ti-185, has been successfully processed using the directed energy deposition (DED) based laser engineered net shaping (LENS) process, obviating the beta fleck problem associated with Fe micro-segregation that has been reported in conventionally processed counterparts. The large solidification range for this alloy resulted in finer scale equiaxed β grains in the as deposited condition for a range of process parameters, unlike the large columnar grains observed in case of AM of other titanium alloys such as Ti–6Al–4V. Furthermore, based on the process parameters, a homogeneous distribution of fine scale ω or α precipitates form within the β grains, which has been rationalized based on quantitative thermo-kinetic modelling of a multi-layered deposition process. Atom probe tomography results indicate early stages of β/ω compositional partitioning, leading to a higher tensile yield strength, close to 1000 MPa, as compared to the solution treated/quenched condition of conventionally processed Ti-185. Homogeneous fine scale α precipitation, with a more pronounced compositional partitioning, resulted in an exceptional yield strength exceeding 1200 MPa in the as-processed condition.

Microstructure and defects in a Ni-Cr-Al-Ti γ/γ’ model superalloy processed by laser powder bed fusion

Additive manufacturing (AM) of non-weldable high-γ’ Ni base superalloys is challenging due to various issues, but notably because of their inherent cracking propensity. Typically, the segregation of melting point-depressant elements to grain boundaries (GB) drastically increases the solidification interval, allowing the high processing-induced stresses in the parts to pull apart the liquid film at GBs. To achieve a better understanding of the consolidation process of nickel superalloys as well as the origin of defects and cracks, a simplified model γ/γ’-strengthened Ni-Cr-Al-Ti alloy with reduced solidification interval, related to the commercial CM247LC alloy, is investigated under a large parameter survey. The consolidation behavior is typical of nickel superalloys produced by AM, with the optimal condition being a compromise between cracking and porosity. The cracking mechanism is, however, changed to solid-state cracking, localized at high-angle GBs, and likely due to the lack of GB strengthening phases and the inherently low strength of this simplified alloy. Transmission electron microscopy and atom probe tomography reveal elemental segregation of Ti, and to a lower extent Cr and Al, to the solidification cell boundaries, in agreement with Calphad calculations. No γ’ precipitates are observed in the as-processed condition, indicating that all elements remain in solid solution. No chemical differences are observed between cracked and non-cracked boundaries. Trace amounts of oxygen contained in the powder lead to Al2O3 slag formation, as well as nano oxide dispersoid incorporation. Sulfur, a critical contaminant in superalloys, is detected but rendered harmless by the formation of TiS nanoprecipitates.

Microstructural evolution in single tungsten fiber-reinforced tungsten composites during annealing: recrystallization and abnormal grain growth

Tungsten is considered as plasma-facing material in future fusion reactors. Due to the high operation temperatures, the occurrence of microstructural restoration processes as recovery, recrystallization and grain growth will unavoidably alter the desired microstructure obtained after processing and impede otherwise beneficial mechanical properties. Potassium-doping proved to be efficient in hindering or at least delaying such phenomena. Tungsten fiber-reinforced tungsten composites with drawn tungsten wires embedded in a tungsten matrix show a certain pseudo-ductility. Cylindrical single fiber composites with a single potassium-doped drawn tungsten wire in a chemically vapor deposited tungsten matrix, with or without a rare-earth oxide interlayer, were investigated as model systems. Individual specimens were annealed at 1400 °C up to four weeks and changes in their microstructure tracked by electron backscatter diffraction. In the as-processed condition, the tungsten matrix showed large wedge-shaped grains stretching radially from either the interface between matrix and wire or the oxide interlayer to the outer surface with very small grains in the vicinity of the interface/interlayer. Upon heating, two zones with larger grains compared to the as-processed condition developed: in the wire regions close to its perimeter primary recrystallization led to formation of new grains with orientations deviating slightly in alignment of their crystallographic <110> directions with the wire axis compared to the drawn wire. In the matrix, abnormally grown grains consumed the as-deposited microstructure in the vicinity of the interface/interlayer. Without an interlayer, abnormally growing grains from the matrix invaded the recrystallizing wire progressively consuming the wire. Both erbia and yttria interlayers efficiently prevented abnormally growing grains from invading the wire (except at few occasions where the oxide interlayer presented imperfections). In this manner, the presence of an interlayer becomes crucial for retaining an interface essential for the pseudo-ductility of the composite.

Influence of Particle Reinforcement and Heat Treatment on the Wear Resistance of Inductively Melted Hardpaint Coatings

Wear-resistant coatings can reduce the high economic damage caused by wear processes. In this study, various protective layers based on the alloy X400CrVMo17-15-2 were investigated. Commonly, the prealloyed metal powder is used for plasma transferred arc powder surfacing. However, in this work, the cost-efficient hardpaint technology was used to produce particle-reinforced (fused tungsten carbides) and non-reinforced coatings. To analyze the wear behavior, the coatings were subjected to abrasion wear and scratch tests. For the abrasion wear test, a grinding pin (Al2O3) is pressed with a defined force against the surface of the rotating sample for 6 h. For the scratch test, a loaded diamond pyramid indenter was employed to create a circular groove on the coatings at a predefined speed. The wear grooves were analyzed with the aid of laser scanning microscopy. In comparison to the coatings in the as-processed condition, the non-reinforced protective layers were investigated after quenching, with and without deep cryogenic treatment, and tempering. The determination of proper heat treatment parameters was supported by computational thermodynamics. It has been confirmed that it is possible to improve the wear resistance of the unreinforced coatings by heat treatment. However, the reinforced layers showed the highest resistance against abrasion.

Phase stability and conductivity of rare earth co-doped nanocrystalline zirconia electrolytes for solid oxide fuel cells

Abstract Solid oxide fuel cell (SOFC) is a green energy technology that directly coverts chemical energy into electricity. Scandia stabilized zirconia (SSZ) shows the highest conductivity among zirconia based electrolytes for SOFCs. However, the stability of the cubic phase, which is the desirable phase for high conductivity, can be an issue in SSZ electrolytes due to its transformation to other low-conducting phases at higher temperatures. In the present investigation, SSZ electrolyte was co-doped with ytterbia, gadolinia and ceria with an objective of improving the high-temperature phase stability. Both the doped and co-doped compositions exhibited a single cubic phase in the as-processed condition. The phase stability at high temperature was studied by aging the sintered pellets at 900 °C for 500 h in air. X-ray diffraction and transmission electron microscopy analysis revealed formation of small amount of the low-conducting tetragonal phase in 1 mol % ytterbia and gadolinia co-doped compositions on ageing which resulted in conductivity degradation. Increasing the doping level to 2 mol% prevented the formation of the tetragonal phase. The ceria co-doped composition (1 mol%), on the other hand, was clean without any sign of the secondary phases even after high-temperature ageing. The rhombohedral ‘β’ phase formed in the binary composition (SSZ) after sintering but was absent in all the co-doped compositions. The conductivity of the co-doped samples was higher than the binary SSZ. Thus, it can be said that rare earth co-doping is an effective way of improving the phase stability and conductivity of SSZ electrolytes.

Microstructure, properties and thermoluminescent response of sintered synthetic topaz (Al2SiO4F1.44 (OH)0.56)/Al2O3 compounds

Because of variations in composition and the ensuing properties of mineral topaz, synthetic topaz offers to be a promising candidate for advanced applications. The thermoluminescent response of sintered synthetic Al2SiO4F1.44(OH)0.56 (topaz)/Al2O3 (corundum) compounds, was studied for the first time. From an L8 Taguchi experimental design, topaz specimens synthesized by CVD were thermally treated varying temperature (850, 1000 °C), time (30, 60 min), powder compaction pressure (250, 500 MPa), atmosphere (N2, Ar) and tablet position in the reactor (0, 90°). XRD analysis confirms the presence of Al2SiO4F1.44(OH)0.56 as a single phase in the as-processed condition and of Al2O3 besides topaz, in the sintered state. Specimens sintered at 850 °C feature prismatic bars with pyramidal ends, of uniform distribution and average length between 5.03–6.02 μm. A series of possible chemical reactions giving place to the topaz formation and subsequent sintering-associated reactions is put forward. Associated with [AlO4]° centers, the presence of two well resolved and independent peaks between 150−250 °C in the TL glow curves and the linear response in all tested samples as dose increases (0.02 Gy–66 Gy), encourage further research to increase dose range linearity and paves the way for possible application of the sintered synthetic topaz/corundum compounds in dosimetry.

Hot corrosion behaviour of wire-arc additive manufactured Ni-based superalloy ATI 718Plus®

The hot corrosion behaviour of wire-arc additive manufactured and wrought ATI 718Plus® are studied. ATI 718Plus® produced by the additive manufacturing process, in the as-processed condition, exhibits a significantly lower hot corrosion resistance in comparison to the wrought alloy. Analytical electron microscopy and spectroscopy techniques, with corroboration by thermodynamic calculations, are used to identify the underlying cause of the poor hot corrosion resistance. Based on the understanding accrued from the analyses, post-processing heat treatments are used to improve the hot corrosion resistance, which is valuably pertinent to the application of ATI 718Plus® produced by additive manufacturing in hot corrosive environments.

Improved dynamic impact behaviour of wire-arc additive manufactured ATI 718Plus®

The dynamic response and impact resistance of wire-arc additive manufactured (AMed) and wrought ATI 718Plus in different heat treatment conditions are characterised by using a direct impact Hopkinson pressure bar system. In addition, microstructural analyses of the alloys, before and after impact, are characterised by using advanced microscopy techniques, including scanning electron and transmission electron microscopies. The experimental results show that the impact resistance of the AMed alloy in the as-processed condition is inferior to that of the wrought alloy. The lower impact resistance is attributed to the presence of eutectic solidification constituents in the interdendritic regions and to the inhomogeneous distribution of the strengthening precipitates in the deposit. After the application of the recommended heat treatment for ATI 718Plus, excessive formation of η-phase particles are observed in the microstructure in addition to Laves phase particles. Since the recommended heat treatment for ATI 718Plus is not sufficient to eliminate the deleterious phases and optimise the properties of the alloy, a novel heat treatment procedure is proposed. Dynamic impact study of the AMed alloy after the application of the proposed approach shows that the alloy exhibits a dynamic response and impact resistance comparable to those of the wrought alloy. Furthermore, under high impact momentum, both the wrought and the AMed alloys fail due to the adiabatic shear band. A transmission electron microscopy analysis of the deformed alloys suggests the dissolution of the γ' precipitates in the shear band as well as in the adjacent regions to the shear band. Increase in the rate of dissolution of the precipitates due to strain-assisted diffusion coupled with an increase in the adiabatic temperature during deformation, are likely causes of the dissolution of the precipitates in the shear band regions.

Microstructure characterization of SLM-processed Al-Mg-Sc-Zr alloy in the heat treated and HIPed condition

Sc- Zr-modified Al-Mg alloy, processed by selective laser melting, offers excellent properties in the as processed condition, due to the formation of a desirable microstructure. As in conventional processing, such alloys are age hardenable, thereby precipitating a high fraction of finely dispersed coherent Al3(Scx Zr1-x) intermetallics, which serve for the improvement of the mechanical strength. Electron backscatter diffraction measurements and transmission electron microscopy were used to determine the effects of heat treatment and HIP on the microstructures of SLM processed specimens. In addition, the chemistry and number density of Al3Sc particles was analysed by atom probe tomography. The results show that the bi-modal grain size distribution observed in the as-processed condition can be maintained even after a heat treatment, due to a high density of intragranular Al3(ScxZr1-x) precipitates, and various other particles pinning the grain boundaries. A HIP post-processing can lead to grain growth in certain coarser grained areas, probably due to a local imbalance between driving and dragging forces, hence higher defect density and fewer pinning precipitates. Applying a heat treatment results in an increase of the density of ≤5 nm sized intragranular Al3(Scx Zr1-x) particles by a factor of 4–6, reaching 3·1023 m−3 to 5·1023 m−3.

Laser surface modification of 316L stainless steel.

Medical grade 316L stainless steel was laser surface melted (LSM) using continuous wave Nd-YAG laser in argon atmosphere at 1 and 5 mm/s. The treated surfaces were characterized using electron backscatter diffraction to study the influence of top surface crystallographic orientation and type of grain boundaries on corrosion resistance, wettability, and biocompatibility. The laser scan velocity was found to have a marginal influence on the surface roughness and the type of grain boundaries. However, the crystal orientation density was found to be relatively high in 1 mm/s samples. The LSM samples showed a higher concentration of {101} and {123} planes parallel to the sample surface as well as a higher fraction of low-angle grain boundaries. The LSM samples were found to exhibit better surface wettability and enhanced the viability and proliferation of human fetal osteoblast cells in vitro when compared to the untreated samples. Further, the corrosion protection efficiency of 316L stainless steel was improved up to 70% by LSM in as-processed condition. The increased concentration of {101} and {123} planes on surfaces of LSM samples increases their surface energy, which is believed to be responsible for the improved in vitro cell proliferation. Further, the increased lattice spacing of these planes and high concentration of low-energy grain boundaries in LSM samples would have contributed to the better in vitro corrosion resistance than untreated 316L stainless steel. Our results indicate that LSM can be a potential treatment option for 316L stainless steel-based biomedical devices to improve biocompatibility and corrosion resistance. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 569-577, 2018.

The Mechanical Properties of Minimally Processed RDX

We report for the first time the mechanical properties of RDX crystals in a conventionally processed, sub-millimeter form that have had no additional mechanical processing. Nanoindentation of RDX powders was used to measure the elastic modulus (19.1±1.9 GPa), hardness (0.741±0.098 GPa), and yield point (onset of plastic deformation) on the as-grown faces of seven different RDX crystals, selected to provide random orientations. Properties within each crystal showed narrow distributions, while the range of properties across all crystals is indicative of testing a variety of orientations. The elastic modulus and hardness are within the range of other published reports on bulk and mechanically polished RDX. The distribution in yield point behavior, with the onset of plasticity occurring between 0.1 and 0.7 GPa, indicates that powders of RDX likely contain a significant number of dislocation sources in the as-processed condition, suggesting that deformation sources are prevalent in the energetic component of plastic bonded explosives prior to incorporating into pressed forms.

The Effects of Water Vapor on the Oxidation Behavior of Alumina Forming Austenitic Stainless Steels

The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800 °C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a “good chromia former” at 650 °C, particularly in H2O-containing atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650 °C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar–4%H2–3%H2O the areas of continuous alumina were reduced and Fe oxide-rich nodules and regions of Cr, Mn-rich oxides formed. In some regions internal oxidation of the aluminum occurred in the H2O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800 °C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800 °C in atmospheres, which contained water vapor (Air–10%H2O, Ar–3%H2O and Ar–4%H2–3%H2O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H2O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800 °C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition. The reason for this is the presence of different phases in the bulk of the two specimens.

Rationalization of Microstructure Heterogeneity in INCONEL 718 Builds Made by the Direct Laser Additive Manufacturing Process

Simulative builds, typical of the tip-repair procedure, with matching compositions were deposited on an INCONEL 718 substrate using the laser additive manufacturing process. In the as-processed condition, these builds exhibit spatial heterogeneity in microstructure. Electron backscattering diffraction analyses showed highly misoriented grains in the top region of the builds compared to those of the lower region. Hardness maps indicated a 30 pct hardness increase in build regions close to the substrate over those of the top regions. Detailed multiscale characterizations, through scanning electron microscopy, electron backscattered diffraction imaging, high-resolution transmission electron microscopy, and ChemiSTEM, also showed microstructure heterogeneities within the builds in different length scales including interdendritic and interprecipitate regions. These multiscale heterogeneities were correlated to primary solidification, remelting, and solid-state precipitation kinetics of γ″ induced by solute segregation, as well as multiple heating and cooling cycles induced by the laser additive manufacturing process.