激光粉末床熔融成形Al-Cu-Mg-Sc-Li合金组织与性能研究

Study on Microstructure and Properties of Al-Cu-Mg-Sc-Li Alloy Fabricated by Laser Powder Bed Fusion

摘要:

Al-Cu-Mg体系合金发展较为成熟，目前已被广泛应用于航空航天等领域。激光粉末床熔融(LPBF)技术是一种快速成形技术，其成形产品精度高且表面质量优，被广泛地应用于航空航天、生物医药、汽车制造等领域。利用LPBF快速加热和冷却的特性，可以实现合金元素在基体中高度固溶，形成过饱和固溶体，从而提高合金的性能。Cu是具有很大潜力的强化LPBF成形铝合金的元素，而目前关于LPBF成形高Cu含量（质量分数≥4%）铝合金的研究鲜有报道。因此，利用LPBF技术制备一种新型高Cu含量（质量分数6%）的Al-Cu-Mg-Sc-Li合金，通过优化工艺参数来获得高度致密且无裂纹的合金。通过致密度测试、扫描电镜分析（SEM）和室温拉伸性能测试等手段，研究不同LPBF打印参数变化对Al-Cu-Mg-Sc-Li合金显微组织及力学性能的影响。研究结果表明，在激光功率为240 W、扫描速率为700 mm·s^-1时，Al-Cu-Mg-Sc-Li合金致密度（99.53%）高且无裂纹，显微组织具有特征的双峰组织形态，主要由细小的等轴晶和狭长的柱状晶构成，Al₂CuMg相分布在等轴晶和柱状晶晶界处，Al₃Sc相分布在等轴晶晶界处。拉伸测试结果表明，Al-Cu-Mg-Sc-Li合金的平均抗拉强度为124.7 MPa、断后伸长率为3.3%，这是大量Al₂CuMg相在晶界处形成诱导应力集中而引发微裂纹所致。揭示高含量Cu元素的分布及析出相对Al-Cu-Mg-Sc-Li合金力学性能的影响，为Al-Cu-Mg体系合金在航空航天等领域中应用提供试验数据与技术支持。(专精特新·特殊环境材料服役行为专辑十五之十二)

Abstract:

The evolution of Al-Cu-Mg alloy systems has attained a state of maturity， leading to their ubiquitous applications across aerospace and diverse industries. Laser Powder Bed Fusion （LPBF）， an exemplary rapid prototyping technology， yields products characterized by unparalleled precision and outstanding surface finish， thereby finding extensive utilization in sectors encompassing aerospace， biomedical， automotive manufacturing， mold fabrication， and beyond. Leveraging LPBF's rapid thermal cycling capabilities， alloying elements are effectively solubilized to a high degree within the matrix， fostering the creation of supersaturated solid solutions that bolster the performance attributes of LPBF-produced alloys. Extensive research underscores the potential of Cu as a potent strengthener in LPBF aluminum alloys. Nevertheless， reports concerning LPBF aluminum alloys enriched with high Cu content （≥4 wt.%） remain scarce. Consequently， this study endeavors to formulate a novel Al-Cu-Mg-Sc-Li alloy featuring an elevated Cu content （6 wt.%） via the LPBF methodology， accompanied by the optimization of process parameters to achieve a densely packed， crack-free material. To unravel the impact of varying LPBF printing conditions on the microstructural architecture and mechanical behavior of the Al-Cu-Mg-Sc-Li alloy， we conducted comprehensive investigations involving densification assessments， Scanning Electron Microscope （SEM） analysis， and ambient temperature tensile tests. At an optimized laser power of 240 W and scanning speed of 700 mm·s^-1， the alloy attained a remarkable density of 99.53%， devoid of cracks. Its microstructure is noteworthy for its characteristic bimodal feature， comprising fine equiaxed grains juxtaposed with slender columnar grains. Notably， the Al₂CuMg phase borders both grain types， while the Al₃Sc phase is confined to the equiaxed grain boundaries. Tensile testing revealed a mean tensile strength of 124.7 MPa and an elongation at fracture of 3.3% for the Al-Cu-Mg-Sc-Li alloy. This performance profile stems primarily from the microcrack formation triggered by stress concentrations induced by the copious presence of Al₂CuMg phases at grain interfaces. This research underscores the significance of high-Cu content distribution and precipitate phase formation on the mechanical properties of the Al-Cu-Mg-Sc-Li alloy， furnishing valuable experimental insights and technical underpinnings for the production and deployment of Al-Cu-Mg system alloys across aerospace and associated industries.