Precipitation-hardened Alloys Research Articles

High-strength medium-entropy alloy designed by precipitation-strengthening mechanism via machine learning

Precipitation-hardened high/medium entropy alloys (PH-HEAs/MEAs) have attracted extensive interest due to their excellent mechanical properties at both room and high temperatures. Strengthening mechanism models can be used to guide the discovery and design of new alloys, however, the parameters of the models are often lacking, limiting their use for compositional screening from a large space. We proposed a strategy combining machine learning with precipitation strengthening mechanism for high-performance PH-HEAs/MEAs. Using this strategy, we successfully synthesized an alloy Al5Ti8Co40Fe7Ni40 with a yield strength approaching 1.15 GPa, 10% higher than the best value of the existing AlTiCoCrFeNi HEAs/MEAs strengthened by L12-type nanoprecipitates. The contribution of precipitation strengthening from the L12 phase is approximately 717 MPa. Our strategy that unites the strengthening mechanism and machine learning may inspire the rapid design and discovery of precipitation-hardened alloys.

Thermal stability of microstructure and their influences on mechanical properties of precipitation-hardened medium-entropy alloy Ni43.4Co25.3Cr25.3Al3Ti3

The thermal stability of the coherent, nanoscale, L12 precipitates and fine grains in a strong, ductile medium-entropy alloy (MEA) Ni43.4Co25.3Cr25.3Al3Ti3 were analyzed and related to the room-temperature mechanical properties. Increasing the aging temperature and prolonging the soaking time produced more L12 precipitates and reduced the matrix lattice constant. The fine grains exhibit excellent thermal stability with a very low coarsening rate (1.73 × 10−24 m3/s at 700 °C, 4.78 × 10−23 m3/s at 800 °C, and 4.32 × 10−22 m3/s at 900 °C), which mainly results from the strong pinning from the high density of precipitates and high activation energy for grain growth (∼272 kJ/mol). The L12 precipitates remain spherical and have a coherent relationship with the matrix during ripening from tens to hundreds of nanometers. They exhibit better thermal stability (6.45 × 10−30 m3/s at 700 °C, 2.03 × 10−28 m3/s at 800 °C, and 7.16 × 10−27 m3/s at 900 °C) than the L12 precipitates in nickel-based superalloys by 1–2 orders of magnitude with an activation energy of 341 kJ/mol. The critical size for the transition from dislocation shear of the L12 precipitates to dislocation looping is 23.5–30.4 nm. No significant coarsening of either the grain size or L12 precipitates caused a small decrease in the YS and UTS of MEA aged at 700 °C. In comparison, both the YS and UTS of MEA aged at 800–900 °C dramatically decreased, which is caused by the coarsening of the L12 nanoparticles and the average grain size. This decrease in strength was accompanied by a slight increase in ductility at all three aging temperatures.

Hydrogen-enhanced decohesion mechanism of the Ni-Ni3X interfaces in precipitation-hardened Ni-based alloys

Ni and its alloys are susceptible to hydrogen embrittlement. In this study, we investigate the phenomenon of hydrogen-enhanced decohesion at inter-phase interfaces in precipitation-hardened Ni-based alloys using a systematic first-principles approach. We demonstrate that hydrogen atoms primarily prefer to localize at the Ni3Al phase in the Ni/Ni3Al interface, while they tend to be trapped by Ni in the Ni/Ni3Nb interface. Our findings reveal that hydrogen induces inter-phase embrittlement in both the Ni/Ni3Al and Ni/Ni3Nb interfaces. Moreover, we show that the hydrogen-enhanced decohesion at these interfaces is influenced by various factors such as hydrogen pressure, hydrogen content, temperature, and strain. Finally, we discuss in detail the hydrogen-enhanced decohesion mechanisms at the Ni/Ni3Al and Ni/Ni3Nb interfaces, including their electronic structures, energy landscape of hydrogen at trapping sites, and schematics of crack propagation.

Effect of cold rolling on nucleation, growth and coarsening of S-phase precipitates in Al- Cu- Mg alloy (AA2024): From heterogeneous nucleation to homogeneous spatial distribution

The effect of cold rolling on the precipitation kinetics of the hardening phase has been studied in industrial AA2024. Due to the relatively simple precipitation sequence and the use of the alloy in naturally aged (T3) and peak-aged (T8) states, it was possible to unambiguously analyse the effect of pre-deformation on the nucleation/growth and coarsening of the S-phase. Faster coarsening kinetics due to dislocations induced by cold rolling were observed before the recovery had been completed, leading to lower hardness of pre-deformed AA2024-T8 compared to that without pre-deformation for the same ageing conditions. The nucleation and growth of S-phase were also faster after cold rolling. Moreover, the heterogeneous nucleation resulting from pre-deformation finally led to a fine and homogeneous spatial distribution of hardening precipitates and thus to higher hardness values. Furthermore, cold rolling resulted in a different aspect ratio of S-phase precipitates during both growth and coarsening. The current study was conducted on AA2024, one of the most studied Al-Cu-Mg alloys, where only one equilibrium phase, the S-phase, precipitates, but the findings may be applicable for other precipitation-hardened alloys as well.

Warm Aging of Pre-aged AA6013 Sheet and Its Relevance to Room Temperature and Warm Forming Applications—Experimental and Modeling Analyses

AbstractWarm forming has been shown to be an effective way to increase the formability of various aluminum sheet alloys. If applied to precipitation hardenable alloys, aging and/or coarsening may occur during heating and/or forming processes. As such, there is a potential to leverage the warm forming process to artificially age precipitation hardenable alloys. In this study, the aging characteristics of a pre-aged Al-Mg-Si-Cu alloy (designated AA6013-PA and comprising a 4 h, 100 °C pre-aging cycle following solutionization) were examined using: (i) room temperature tensile and (ii) bendability experiments, as well as (iii) elevated temperature tensile and formability experiments in the temperature range of 220-280 °C. In the pre-aged condition, the alloy exhibited very high work hardening, elongation and bendability. It was found that T6-like properties can be obtained with short duration secondary aging of the AA6013-PA starting temper (410 s at 235 °C), followed by a paint bake cycle (30 min at 177 °C). In such heavily aged conditions, the bendability is found to be moderate and consistent with a T6 temper. Bendability of the pre-aged alloy is shown to be enhanced by reducing the extent of aging, which may be beneficial for applications requiring energy absorption during crash, for example. In the pre-aged condition, AA6013 displayed a 55% improvement in room temperature formability, relative to the T6 condition, for near plane-strain loading using a Nakazima punch, although neither temper exhibited formability improvements through warm forming. The aging kinetics of AA6013-PA were determined from mechanical test data and used to calibrate an aging kinetics model. A strong obstacle model was used to relate precipitation state to yield strength, for artificial aging in the range 220-280 °C. The incremental strength increase due to exposure to an automotive paint cure cycle was also modeled and found to yield accurate results. Warm deformation, as well as room temperature deformation, were shown to enhance the paint bake response of the alloy, reducing the time to the peak aged condition by up to 14% for artificial aging at 177 °C.

Numerical study on local short-term heat treatments for joining by forming of high-strength 7xxx aluminum

7xxx aluminum alloys have very high specific strengths, making them interesting for manufacturing car bodies. However, the limited formability of the precipitation hardenable alloys in the artificially aged T6 temper is challenging for forming and joining processes. The pre-conditioning of aluminum sheets by a short-term retrogression is a promising approach to enhance the process limits of joining by forming technologies. In addition, localizing the heat treatment enables the control of the material flow. However, for a targeted material flow, a deeper understanding of the relation between the heat treatment layout and its influence on joining processes is needed, which can be achieved with the aid of numerical analyses. Therefore, within the scope of this work, an approach for the numerical simulation of locally limited heat treatment layouts for the control of the material flow of high-strength aluminum sheets in joining by forming process is shown. The investigations are conducted for the simulation software LS-DYNA and the innovative shear-clinching process. Process models for the local retrogression heat treatment of punch-sided AA7075 T6 and the subsequent shear-clinching as well as an approach to couple the individual models are presented. By performing a localized retrogression from the T6 temper, the radial material displacement of the upper sheet in the shear-clinching process can be reduced in comparison to joining AA7075 in the W temper. The control of the material flow in the joining process thereby causes the improvement of geometric features, which are critical for the joint strength.

Short-time induction heat treatment of high speed steel AISI M2: Laboratory proof of concept and application-related component tests

High-speed steels (HSS) such as AISI M2 are generally used for cutting and forming tools or broaches with the highest demands on load bearability and hot-hardness. The requirements for high-speed steels are, on the one hand, extremely high hardnesses of over 800–900 HV and, on the other hand, the thermal stability of the microstructure up to 500 °C. This combination is achieved by complex precipitation-hardenable iron-based alloys. Common heat treatment practices for high-speed steels use salt baths or vacuum ovens, which are energetically unfavorable and require subsequent cleaning. The study consists of short-time hardening and short-time tempering on a laboratory scale by means of dilatometry and thereupon an implementation in an industrial induction hardening machine. The laboratory scale experiments demonstrate the feasibility of bringing sufficient alloying elements into solution by means of several heat treatment cycles despite short holding times of 1 s and less. Combined tests of short time hardening and tempering show a hardness of up to 850 HV10 that are competitive with the conventional heat treatment route. First attempts to transfer the process to an industrial setup exhibit some peculiarities in the process control, but reveal promising results with a surface hardness of up to 750 HV10.

Development, Processing and Aging of Novel Zn-Ag-Cu Based Biodegradable Alloys.

The use of biodegradable materials for implants is a promising strategy to overcome known long-term clinical complications related to permanent implants. Ideally, biodegradable implants support the damaged tissue for a certain period and then degrade, while the physiological function of the surrounding tissue is restored. Although Mg-based alloys nearly ideally lend themselves to biodegradable implants, a few critical shortcomings promoted the development of alternative alloy systems. Due to their reasonably good biocompatibility, moderate corrosion rate without hydrogen evolution and adequate mechanical properties, increasing attention has been paid to Zn alloys. In this work, precipitation-hardening alloys in the system Zn-Ag-Cu were developed relying on thermodynamic calculations. After casting the alloys, their microstructures were refined by thermomechanical treatment. The processing was tracked and directed, respectively, by routine investigations of the microstructure, associated with hardness assessments. Although microstructure refinement increased the hardness, the material proved to be susceptible to aging as the homologous temperature of zinc is at 0.43 Tm. Besides mechanical performance and corrosion rate, long-term mechanical stability is another crucial factor that must be taken into consideration to ensure the safety of the implant and thus requires a profound understanding of the aging process.

Making a coherent L12-nano-precipitates-reinforced Ni-based alloy ultrastrong and ductile by constructing dual heterogeneous structures

It is known that inhibiting rapid decline of strain hardening is crucial in enhancing uniform ductility under uniaxial tension stress for metallic materials with high yield stress. In this study, a high-mechanical-response Ni-based alloy was introduced by fabricating a dual-heterogeneous structure allowing to provide improved strain-hardening capability at both ambient and cryogenic temperatures. Especially at cryogenic temperature, an exceptional strength-ductility synergy with yield strength of 1.85 GPa and ductility of 24% can be achieved, accompanied by a distinctive five-stage strain-hardening response. In such a case, deformation twinning behavior was activated successfully to assist the strain hardening in the Ni base alloy although precipitation-hardening effect was available. Our work sheds light on the strain hardening effect assisted by twinning previously unexpected in coherent precipitation-hardened Ni base alloys, and hence represents a promising route for improving uniform ductility of Ni base alloys with high yield strength.

Influence of carbon contents on the cryogenic mechanical properties of precipitation-hardened CrMnFeCoNi high-entropy alloys manufactured by laser powder bed fusion

The cryogenic mechanical properties of additively manufactured CrMnFeCoNi high-entropy alloys (HEAs) with different carbon contents were investigated. The superior cryogenic ultimate tensile strength of 1.6 GPa of the 1.5 at.% carbon-containing CrMnFeCoNi HEA was attributed to the stabilization of the sub-grains by numerous carbide precipitates and the dislocation-network induced substructure.

Square L12 precipitates inducing high susceptibility to adiabatic shear in 3D printed fine-grained tungsten heavy alloy with high-entropy alloy matrix

Tungsten heavy alloys with a L12 precipitation-hardening high-entropy alloy matrix exhibit high susceptibility to adiabatic shear, but the relationship between the size and morphology of L12 precipitates and the adiabatic shear behavior is not well understood. This work systematically studies the effect of different size and morphology L12 precipitates on the mechanical properties and susceptibility to adiabatic shear of the tungsten heavy alloy with an AlCrFeNiV-system high-entropy alloy matrix (W-HEA). The results show that the W-HEA with square L12 precipitates has tensile strength of 1300 MPa and dynamic compression strength of 2100 MPa at a stain rate of 6000 s−1. The higher interfacial energy of square L12 precipitates leads to the faster re-dissolution of square L12 precipitates into the matrix than ultrafine and lath-like L12 precipitates under temperature rise during shearing, which can sharply soften the shearing location and contribute to the narrowest adiabatic shear band (ASB) with width of 15 μm.

Unexpectedly high precipitation hardening induced by supersaturated solute and strong texture in a Mg-13Gd binary alloy after forging

Obtaining exceptionally high strength in large-scale Mg alloys using conventional free-forging process is an enormous challenge since high-temperature forging is difficult to produce ultrafine grains. In this work, we achieved ultrahigh strength, such as yield strength of 458 MPa and ultimate tensile strength of 493 MPa, in coarse-grained Mg-13Gd forged alloys by maximizing precipitation hardening effect, which exceeds that of conventionally free-forged Mg alloys documented previously. High-temperature forging, while does not refine the grain below the micron level, favors the formation of strong basal texture and suppresses dynamic precipitation to enable supersaturated Gd atoms in the matrix, which provides a favorable precondition for the unexpectedly high precipitation hardening in the following ageing. As a result, further ageing treatment produces a surprisingly high increment of over 170 MPa in yield strength, breaking through the previous highest record in precipitation-hardened Mg alloys. Thus, we creatively proposed a new strategy for fabricating high-strength forged Mg alloys via constructing texture hardening and maximizing precipitation hardening. These results provide important implications for fabricating high-strength Mg forgings.

Superalloy—Steel Joint in Microstructural and Mechanical Characterisation for Manufacturing Rotor Components

The structure of energy rotor components includes different structural materials in the sections, which are subjected to varying levels of thermal loading. The first component section has to include a precipitation-hardened nickel-based alloy, while the second one may be manufactured from other materials. Due to the installation cost, the use of expensive nickel-based materials is not recommended for applications in sections with a lower degree of thermal loading. Therefore, this aspect is still actually from an engineering point of view and is discussed in the paper by means of manufacturing and experimental approaches. The paper follows the welding problems related to a hybrid joint made of superalloy (Alloy 59) and hard rusting steel (S355J2W+N steel). The problem is solved using the MIG process at various parameters. With respect to the joint quality, microstructural features and mechanical parameters of the examined zone are presented. In the case of microstructure analysis, the dendritic and cellular natures of austenite were dominant elements of the joint. Mechanical tests have expressed a 50% reduction in elongation of the steel and alloy steel weld and lowering mechanical parameters. Mechanical parameters of the joint were on the level of their values observed for the steel, while the hardening coefficient followed the hardening curve of the alloy. Decohesion of the steel and mixed weld has reflected the constant proportion of values of axial and shear stress components up to the total separation. It is noted the tensile curves of the alloy and alloy steel joint follow a very similar shape, reporting the same response on the monotonic tension. The materials can be analysed by applying constitutive equations at very similar values of their coefficients. The obtained results enabled elaborating and examining the MIG welding process for thick-walled structures (not smaller than 8 mm) in detail giving all parameters required for technology. Finally, the technology for producing a hybrid joint using difficult-to-weld materials with different physical and mechanical properties, such as nickel alloys and low-alloy steels, is proposed. Results have shown it possible to develop a technology for producing of hybrid joints (supper alloy + hard rusting steel) with assumed physical and mechanical properties for rotors applied in the power boiler. This solution was proposed instead of previously used elements of rotors from expensive materials. It was assumed that the newly proposed and utilised method of welding will allow for obtaining good properties in terms of energy devices.

Influence of SLM printing parameters and hot isostatic pressure treatment on the structure and properties of CuNi3Si1 alloy

CuNi3Si1 is a precipitation-hardenable copper alloy exhibiting a favorable combination of high mechanical strength and electrical conductivity, sought after in the electrical and automotive industries. In this paper, a Selective Laser Melting process was applied to assess the effect of printing parameters on the structure and properties of this alloy. First, the acquired samples were investigated to determine their microstructure and optimize printing parameters. Furthermore, tensile testing, salt spray testing and potentiostatic measurements were carried out to estimate the application potential of the 3D-printed copper alloy. The samples printed using the optimal strategy with the highest volumetric energy density (laser power equal to 300 W and scanning speed to 500 mm/s) were characterized by high corrosion resistance in both printing directions (the vertical and horizontal one), the high tensile strength of 334±1 MPa and density of 8.798±0.001 g/cm3. On the other hand, applying the much lower volumetric energy density of 83 J/mm3 results in the preparation of samples with a density of 8.689±0.002 g/cm3 and tensile strength equal to 306±8 MPa. Finally, the possibility of applying Hot Isostatic Pressure technology as a designated post-processing treatment technology was described. It was confirmed that this method could increase the electrical conductivity of printed CuNi3Si1 alloy 4.7 times.

Optimization of squeeze casting process parameters for the production of Al composite reinforced with bone powder

Al6061 alloy is most commonly used in automotive, marine, and aerospace applications to reduce weight and improve the strength of the composite. Al6061 alloy is a precipitation-hardened aluminium alloy used as a matrix material. Beef bone is a bio-waste which pollutes the environment and the people who live in the vicinity of its manufacturing and disposal sites. Bio-waste has been used in a variety of ways by researchers in recent years, including activated carbon, water purification, reinforcement in composites, fillers, medicines, food products and additives etc. Recycled beef bones that had been abandoned as waste were collected, cleaned, and ground into a fine powder with a particle size ranges between 5 and 50 µm and used as reinforcement to produce the Al composite. Because, beef bone has good tensile and compression strength and is light in weight, which helps improve the strength without much increase in cost of the Al composite. The aluminium composite are fabricated using squeeze casting process and the design of experiment based on Taguchi design are imposed to produce the high quality Al composite. The aluminium composite is fabricated and nine samples were successfully obtained for testing and analysis. The prepared substrates are analysed for hardness and tensile strength. Based on the experimental run the optimized process parameter conditions are found also regression equation is provided for the design. The optimized process parameters are found for melt temperature, squeeze pressure, reinforcement percentage, stirring speed as 700 °C, 100 MPa, 5%, 600 rpm respectively. Also, the highest contribution for improving the strength of the material is percentage of reinforcement.

A high-strength precipitation hardened cobalt-free high-entropy alloy

Recent studies on precipitation-hardened high-entropy alloys (HEAs) demonstrate their high strength and thermal stability, making them promising materials for high-temperature structural applications such as nuclear reactors. However, many existing HEAs contain cobalt (Co), which is unsuitable for nuclear applications because of the long-term activation issue of Co. Co is also expensive and considered a critical material for other applications. Therefore, it is desired to exclude Co from the composition. A Co-free (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8 HEA was developed and studied in this work. In contrast to previous Co-free HEAs, this alloy is close to equiatomic in its composition and promises a more pronounced high-entropy effect. Scanning electron microscopy, transmission electron microscopy, atom probe tomography, and synchrotron-based, high-energy X-ray diffraction were used to characterize this alloy and revealed a complex four-phase structure, with an FCC matrix, γ’ precipitates, and a network of B2 and χ phase particles. This structure granted 2151 MPa compressive strength and good thermal stability, but with limited ductility and slow precipitation kinetics. A strengthening analysis of the alloy shows that the B2 and χ provided the most significant strengthening contribution, adding 312 MPa and 788 MPa respectively. The strengthening effect from the nanoscale γ′ is also considerable, adding 608 MPa in total. This study lays the foundation for the continued development of high-strength Co-free HEAs with improved and satisfactory ductility.

Preparation of Nanosize Bone Powder from Waste and Development of Al Composite through Squeeze Casting Process

Al6061 alloy is most commonly used in automotive, marine, and aerospace applications to lighten the composite and increase its strength. Al6061 alloy is a precipitation-hardened aluminum alloy used as a matrix material. Beef bone is a biowaste that has polluted the environment and the people who live in the vicinity of its manufacturing and disposal sites. Biowaste has been used in a variety of ways by researchers in recent years, including activated carbon, water purification, reinforcement in composites, fillers, additives, etc. Beef bones that had been abandoned as waste were collected, cleaned, and grounded into a fine powder with a particle size of 50–100 nm and used as reinforcement. Squeeze casting process is used to create the newly created aluminum composite (Al6061 + 0%, 5%, 10% of bone powder). The aluminum composite was fabricated and three samples were successfully obtained for further testing and analysis. The prepared Al composites with nanopowder reinforcement are analyzed for surface morphology, elemental identification, hardness, porosity, tensile strength, and compression strength. The percentage of porosity in the composite is improved by 36.7% when compared to the Al6061 alloy. Similarly, the tensile strength of the produced composite is increased to 5.59%. A significant improvement is observed in the wear resistance and hardness of the composite as 54.55% and 48.65%, respectively.

Effect of low-temperature quasihydroextrusion on the structure and physical properties of CuCrZr alloy

The work is devoted to the study of changes in the structural and physical properties of the precipitation-hardened CuCrZr alloy under the influence of low-temperature (77 K) quasihydroextrusion with various degrees of deformation at liquid nitrogen temperature with subsequent aging. Prior to quasihydroextrusion, commercial alloy samples were annealed and quenched from the premelting temperature to obtain a supersaturated solid solution of alloying elements in the copper matrix. After quasihydroextrusion, the microstructure, lattice constant, pole densities, tensile strength and yield strength, microhardness (in different cross-sections of the extrudate), and electrical conductivity of the CuCrZr alloy were studied depending on the degree of deformation by quasihydroextrusion. It is shown that the deformation degree determines the kinetics of decomposition of the supersaturated solid solution and its structure. As a result of extrusion, an anisotropic structure of the matrix and precipitates is formed, which also determines the anisotropy of material properties. Subsequent aging leads to a significant decrease in the anisotropy of properties. With an increase in the deformation degree during extrusion (before aging), a significant monotonous increase in physical and mechanical properties occurs. However, in the range of deformation degrees of 40–50%, an anomalous “jump” of all measured properties and structural parameters is observed. The study proposes a physical mechanism that explains the experimental results. The mechanism is based on the occurrence of two kinetically differently directed processes: dynamic aging and its inhibition due to an increase in the defectiveness of the material. The latter process manifests itself essentially at low temperatures. In general, low-temperature quasihydroextrusion makes it possible to obtain a complex of sufficiently high mechanical and electrical characteristics of the CuCrZr alloy at relatively low degrees of deformation for one extrusion cycle, which is facilitated by low deformation temperature.

In situ nanomechanical characterization of hydrogen effects on nickel-based alloy 725 under different metallurgical conditions

• In-situ nanoindentation test was used to study the H effect on alloy 725 • Both solution-annealed and precipitation-hardened alloy 725 were tested • H effect on surface integrity and nanomechanical properties were studied in detail • Different H behaviors were compared based on H content and microstructure The effect of hydrogen on the surface morphology and nanomechanical properties of Ni-based Alloy 725 under solution-annealed (SA) and precipitation-hardened (API) conditions was thoroughly studied. The investigation involved in situ nanoindentation testing, microscopy characterization, statistical analysis, and numerical simulation approaches. The results showed the distinctive effects of hydrogen on the pop-in and hardness in the SA and API samples. For the SA sample, hydrogen mainly dissolved as solid solute in the matrix, causing enhanced lattice friction on the dislocation motion and increasing the internal stress via lattice expansion. Thus, an enhanced hardness, a reduced pop-in width/load ratio, and numerous surface steps were detected in the presence of hydrogen. For the API sample, the strengthening γ’’ phases were the stress concentrators, and the dislocations nucleated heterogeneously, demonstrating indistinctive pop-in phenomena. Furthermore, the precipitates in the API sample affected the trapping behavior of hydrogen, thereby resulting in the hardness change, which reflected the competition between solution hardening in the matrix and vacancy softening mechanism in precipitates.

Precipitate Size in GRCop-42 and GRCop-84 Cu-Cr-Nb Alloy Gas Atomized Powder and L-PBF Additive Manufactured Material

Laser powder bed fusion (L-PBF) of Glenn Research Copper 42 or 84 (GRCop-42 or GRCop-84) produces a Cr2Nb precipitation-hardened high-conductivity copper alloy with tensile strength superior to other competing copper alloys. Precipitate diameters within GRCop-42 gas-atomized powder increase with powder diameter due to slower cooling rates, however, unlike GRCop-84, no threshold diameter above which extensive precipitate agglomerations form was observed in GRCop-42. Large Cr2Nb crystals were observed in GRCop-42 powder particles, implying formation within the crucible melt. A consistent precipitate volume of ~7% over a range of powder particle diameters indicated a consistent atomization process. Occasional voids were observed in GRCop-42 powder. Precipitate size was refined in L-PBF GRCop-42 to a greater extent than in GRCop-84, improving Orowan strengthening, however, this benefit was lost after heat treatment due to greater coarsening of precipitates. Precipitates in GRCop-42 accumulated on grain boundaries during heat treatment to a greater extent than in GRCop-84.