Microstructural evolution of AA7075 powder as feedstock material for cold spray deposition

IF 4.5 2区工程技术 Q2 ENGINEERING, CHEMICAL

Powder Technology Pub Date : 2025-05-22 DOI:10.1016/j.powtec.2025.121162

J. Judas , M. Tebib , M. Sennour , F. Delloro , J. Zapletal

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引用次数: 0

Abstract

In this investigation, the effects of three different heat treatments on the microstructural evolution of gas-atomized AA7075 powder were carefully studied. Advanced electron microscopy techniques, in combination with differential scanning calorimetry (DSC) and X-ray diffraction (XRD), were employed to identify crystallographic features and precipitates under each heat treatment condition. The as-atomized powder exhibited a dendritic-cellular structure with pronounced microsegregation along cell boundaries, indicating a highly non-equilibrium solidification state. High-resolution TEM (HRTEM) revealed the presence of metastable precipitates (GP zones) within the alloy matrix, which is responsible for the elevated hardness of the as-received powder. Strengthening precipitates were formed due to both rapid cooling during atomization and prolonged natural aging during powder storage. Annealing treatments led to transformations of metastable precipitates into coarse phases and promoted dissolution of the cellular network, resulting in substantial powder softening. Additionally, the precipitation of thermally stable Cr-rich phases was found to inhibit grain coarsening at higher temperatures through grain boundary pinning. The present work suggests that the microstructure and mechanical properties of AA7075 powder can be effectively tailored via suitable heat treatment strategies, which may enhance powder deformability and improve its performance as a possible feedstock material for Cold Spray technology.

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冷喷沉积原料AA7075粉末的显微组织演变

研究了三种不同热处理方式对气体雾化AA7075粉末微观组织演变的影响。采用先进的电子显微镜技术，结合差示扫描量热法（DSC）和x射线衍射法（XRD），对不同热处理条件下的晶体学特征和析出物进行了鉴定。雾化后的粉末呈枝状细胞结构，沿细胞边界有明显的微偏析，表明其处于高度不平衡的凝固状态。高分辨率透射电镜（HRTEM）显示合金基体中存在亚稳沉淀（GP区），这是导致接收粉末硬度升高的原因。由于雾化过程中的快速冷却和粉末储存过程中长时间的自然老化，形成了强化沉淀。退火处理导致亚稳相转变为粗相，并促进细胞网络的溶解，导致大量粉末软化。此外，发现热稳定富cr相的析出通过晶界钉住抑制了晶粒在高温下的粗化。本研究表明，通过适当的热处理策略可以有效地调整AA7075粉末的微观组织和力学性能，从而提高粉末的变形能力，提高其作为冷喷涂技术原料的性能。

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来源期刊

Powder Technology 工程技术-工程：化工

CiteScore

9.90

自引率

15.40%

发文量

1047

审稿时长

46 days

期刊介绍： Powder Technology is an International Journal on the Science and Technology of Wet and Dry Particulate Systems. Powder Technology publishes papers on all aspects of the formation of particles and their characterisation and on the study of systems containing particulate solids. No limitation is imposed on the size of the particles, which may range from nanometre scale, as in pigments or aerosols, to that of mined or quarried materials. The following list of topics is not intended to be comprehensive, but rather to indicate typical subjects which fall within the scope of the journal's interests: Formation and synthesis of particles by precipitation and other methods. Modification of particles by agglomeration, coating, comminution and attrition. Characterisation of the size, shape, surface area, pore structure and strength of particles and agglomerates (including the origins and effects of inter particle forces). Packing, failure, flow and permeability of assemblies of particles. Particle-particle interactions and suspension rheology. Handling and processing operations such as slurry flow, fluidization, pneumatic conveying. Interactions between particles and their environment, including delivery of particulate products to the body. Applications of particle technology in production of pharmaceuticals, chemicals, foods, pigments, structural, and functional materials and in environmental and energy related matters. For materials-oriented contributions we are looking for articles revealing the effect of particle/powder characteristics (size, morphology and composition, in that order) on material performance or functionality and, ideally, comparison to any industrial standard.