Journal of Materials Engineering and Performance最新文献

The increasing demand for multi-material components in advanced engineering systems, particularly in thermal management, power generation, and electronic industries, necessitates the development of reliable strategies for joining stainless steel to copper. Wire arc additive manufacturing (WAAM) has emerged as a promising approach for joining dissimilar metals by enabling controlled heat input, compositional grading, and layer-by-layer fabrication. In the present study, a multilayer deposition strategy was employed to join AISI 304 stainless steel to pure copper using WAAM through a cold metal transfer (CMT) mode. Detailed microstructural characterization using optical microscopy, scanning electron microscopy, and electron backscatter diffraction revealed the formation of a defect-free joint facilitated by a diffusion-driven bonding, exhibiting gradual compositional transition from coarse columnar SS304 grains to comparatively fine equiaxed Cu grains across the interface. Significant grain evolution without any preferred crystallographic orientation was observed on the Cu side, with greater diffusion depth of SS304 into Cu. Microhardness mapping indicated that the interfacial properties were governed by the harder SS304 phase. The hardness values across the interface varied between 109 and 187 HV, indicating a gradual transition from the softer Cu region to the stronger SS304 side. The SS304-Cu bimetallic joint exhibited a UTS of 290 MPa and 0.2% YS of 175 MPa, outperforming WAAM-deposited pure Cu and demonstrating failure in the Cu region rather than at the interface. Radiographic examination confirmed minimal porosity within acceptable limits, demonstrating that defect-free and reliable SS304-Cu joints can be systematically achieved through CMT-based WAAM.

Permeable additive manufacturing is immature relative to the field of additive manufacturing, resulting in unknown operating margins for end-use applications. Permeable additive structures are commonly manufactured via Laser Powder Bed Fusion through varying weld penetrations and hatch spacing. These methods produce permeable structures with unique manufacturability, mechanical properties, and flow resistances. Preliminary results of this work confirm correlations of porosity and permeability. The correlation of porosity and permeability is agnostic to the exact structural composition of the printed material, which may mask flaws beneath the surface of the build. While target permeability can be met for a given porosity, the equivalent pore volume can include large, inconsistently located voids instead of an equivalent volume of smaller, evenly spaced pores. To rephrase, select build parameters may cause internal part delamination that are only visible after metallographic cross-section examination. The delamination inherently reduces mechanical properties that are needed for end-use applications and must be avoided. The previous literature has provided quality overviews of permeable additive manufacturing and point design applications but lacks information on the full scope of manufacturing failure mechanisms. This manuscript expands upon mainstream literature, providing failure mechanisms and performance correlations to develop a holistic view of laser parameter development for permeable additive manufacturing. In short, this work provides detailed manufacturing guidelines, inclusive of post-processing techniques, as well as an evaluation methodology to correlate build parameters to performance parameters for Inconel 718.

A multi-scale model is developed to simulate the solidification structure of single-pass wire-arc surfacing (WAS) of Inconel 625 superalloy. This study focuses on clarifying the fundamental thermo-solid coupling laws of single-pass WAS, which provide a critical basis for its application in wire-arc repair and additive manufacturing. The model emphasizes the dynamic thermal conditions at the solid-liquid interface, extracted from a three-dimensional conduction-based heat transfer model with a double-ellipsoid arc heat source. To isolate the effects of local solidification parameters on dendritic morphology, the complex alloy is modeled as a Ni‐Nb binary system, and the phase-field simulation focuses on single-dendrite growth under a transient temperature gradient G and an interface velocity V_s. Results show that dendritic growth evolves through linear, unstable, competitive, and stable stages, with primary dendrite arm spacing (PDAS) increasing from the top to the bottom of the molten pool as the cooling rate (G·V_s) decreases. Furthermore, higher heat-source power reduces G·V_s, leading to coarser dendrites and larger PDAS. Experimental measurements of PDAS and Nb segregation validate the simulation trends, with a relative error of 6.44%. This work provides a quantitative link between arc-surfacing parameters and dendritic microstructure via a multi-scale phase-field approach, offering a theoretical basis for optimizing the performance of repair layers.

Precipitation-hardened CuCrZr (UNS No. C18150) is a performance-critical copper alloy with good thermal and mechanical properties, making it ideal for space applications where fast heat extraction is essential to maintain the integrity of the component and maintain mechanical properties. However, due to its high reflectivity and thermal conductivity, laser powder bed fusion (L-PBF) processing of Cu alloys is difficult, especially at lower energy inputs. Most prior studies focus on high volumetric energy densities (VEDs), neglecting the low-VED regime, which may help to reduce laser back reflection and associated risks to optical systems in industrial L-PBF systems. This study aims to characterize the L-PBF processing of the CuCrZr alloy across a wide VED range (41.15-202.19 J/mm³). In this study, the samples were fabricated using L-PBF and were subjected to two post-processing routes: solution treatment followed by aging (STA) and direct age hardening (DAH). This study analyzed the densification behavior, microstructural evolution, and mechanical properties. Optical microscopy, scanning electron microscopy, and electron backscatter diffraction were employed for microstructural analysis. A maximum relative density (RD) of 99.88% was achieved at a VED of 171.3 J/mm³. Direct aging at 450 °C for 4 h resulted in the highest hardness (189 HV0.2), showing a 119% increase over the as-printed condition. Mechanical performance, including yield strength and ductility, peaked near a VED of 159.72 J/mm³ and plateaued at higher energy levels. EBSD revealed a crystallographic texture shift from <111> //[001] in the as-printed condition to <101> //[001] post-aging, while fracture morphology transitioned from ductile to mixed mode. An increase in thermal conductivity was noted for L-PBF samples, compared to wrought CuCrZr alloy. These results establish a robust L-PBF processing window for the CuCrZr alloy, which would be useful for additive manufacturing of critical space components made from this high-conductivity alloy.

Porous metal structures provide unique capabilities for energy absorption, thermal management, and fluid transport, particularly for aerospace platforms. Laser powder bed fusion additive manufacturing has enabled unprecedented spatial control of porosity, surpassing the capabilities of conventional porous metal foam manufacturing processes. Two distinct approaches exist for fabricating porous metals via powder bed fusion: (1) geometrically-defined porosity, where porous structures are explicitly included in computer-aided design and manufactured with controlled lattice/pore features, and (2) geometrically-undefined porosity, where porosity arises as an artifact of strategically adjusted processing parameters during manufacturing. While geometrically-defined porosity fabrication of lattice structures via powder bed fusion has been extensively reviewed, parameter-based geometrically-undefined porosity fabrication remains comparatively underexplored despite its ability to generally achieve pore sizes ranging from 1 to 100 µm and total porosity between 0 and 50%. By systematically adjusting key processing parameters, including laser power, scan speed, hatch spacing, and layer thickness, researchers can tailor pore density, distribution, and morphology within the fabricated structures. Geometrically-undefined porosity offers distinct advantages, including the ability to achieve finer feature sizes, gradient porosity transitions, and potentially reduce manufacturing complexity for certain applications. This review provides a comprehensive overview of parameter-based geometrically-undefined porosity formation in laser powder bed fusion, synthesizes experimental findings across multiple alloy systems, examines the influence of porosity on mechanical, thermal, electrical, and permeability properties, and discusses research gaps and potential applications for this emerging technique.

This study investigated the Cu-1.5Ni-0.32P alloy processed via hot rolling, solution treatment, cold rolling, and aging, focusing on the influence of cold rolling deformation degree and aging parameters on its microstructure and properties. The results show that the properties of as-cast Cu-1.5Ni-0.32P alloy are uneven due to the enrichment of coarse Ni-P second phase at grain boundaries. After hot rolling with 50% deformation at 900 °C for 2 h and solid solution treatment at 900 °C for 1 h, the second phase is completely dissolved and fine equiaxed grains are formed. The hardness is increased to 125.6 HV, but the conductivity is reduced to 30.1% IACS. After further optimization by 75% cold rolling and aging, it is found that spherical nano-Ni₃P phase precipitates after aging at 450 °C for 6 h, the hardness reaches a peak of 210.7 HV, and the conductivity increases to 65.8% IACS, representing a 138% increase in hardness and a 51% increase in electrical conductivity compared to the as-cast alloy. In this state, the alloy maintains high electrical conductivity while achieving a significant increase in strength, demonstrating outstanding combined properties of high strength and high conductivity. When the aging time was prolonged to 9 h, it was transformed into rod-like Ni₂P phase, which was coherent with the Cu matrix, and the texture was transformed from {001} < 100 > Cube to {112} < 111 > Copper. This study provides important reference for achieving synergistic enhancement of strength and electrical conductivity in Cu-Ni-P alloys through optimized process routes.

Future crewed missions and eventual long-term habitation of the Martian surface will rely on the ability to produce and repair components and structures on-site with materials sourced from the local environment, i.e., in situ resource utilization (ISRU). Synergizing additive manufacturing (AM) processes with ISRU techniques satisfies these requirements while also allowing for on-demand, rapid prototyping and net-shape construction. Direct regolith printing of ceramics and elements harvested for metallic material feedstocks has been shown to be viable in the past, and carbothermal reduction (CR) has been a successful endeavor for oxygen (O₂) generation thus far. In this study, a mixture of JSC-Mars-1A Martian regolith simulant and carbon (C) was subjected to Laser Powder Bed Fusion (L-PBF) to explore the application of AM and CR simultaneously. The regolith and C sources were characterized prior to constructing samples of feedstock-only and feedstock-C mixture, coined Carbothermally Produced Structural (CarPS) material, for x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDS), and compression testing. Results show significantly improved sample build quality in the CarPS samples with a reduction in compressive fracture stress using the same build parameters with evidence of reduced bulk oxygen content.

An extruded AZE311 Mg alloy has been developed and prepared to examine the effect of the precipitated phase on corrosion and hot deformation behavior. High-temperature compression experiments show that dynamic recrystallization (DRX) occurs at various experimental parameters (473 to 673 K and 1 × 10⁻⁴ s⁻¹ to 1 × 10⁻³ s⁻¹). The deformation mechanism is dominated by dislocation slip and/or twinning. Al₁₁Nd₃ precipitates with two different sizes could impede nucleation and the growth of DRXed grains. The serrated flow at low temperature and low strain rate is due to the interaction between dislocations and precipitates. The corrosion current density decreases with the addition of Nd elements. Moreover, the continuous precipitation of the Al₁₁Nd₃ phase at grain boundaries reduces the corrosion rate in 3.5 wt.% NaCl solution, thereby enhancing the corrosion resistance of AZE311 alloys.

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