摘要
目的通过优化激光粉末床熔融工艺参数,制备无欠熔合孔、无裂纹且高致密度的MNiHEA高温高熵合金,以降低缺陷率,优化力学性能,为耐高温合金的激光粉末床熔融增材制造工艺开发提供参考与借鉴。方法选用MNiHEA预合金粉末为原料,通过正交实验设计激光功率与扫描速度等工艺参数,制备单道与立方块样品,同时引入线能量密度作为参考指标,研究了激光功率与扫描速度对单道熔池截面与表面形貌以及块体欠熔合孔、微裂纹和致密度的影响规律,并对最佳工艺参数下的高致密度样品进行了微观组织分析。结果当扫描速度为1600 mm/s时,在100~400 W的激光功率范围内,均观察到球化现象。当激光功率分别增大至200~250 W与300~400 W、扫描速度分别降至1400 mm/s与1200 mm/s时,球化现象依然明显。当线能量密度为0.25~0.33 J/mm、激光功率为150~250 W、扫描速度为600~800 mm/s时,可以获得无欠熔合孔、无微裂纹且致密度>99.9%的试样。试样内部的孔洞主要为球形的匙孔与凝固气孔。此外,共获得4组高致密度试样,其微观组织呈现出典型的“鱼鳞状”特征,且随着线能量密度的增大,熔池深度逐渐增加。熔池内部及边界区域由亚稳微米级位错胞组成。结论高扫描速度更易引发球化现象,且球化的临界扫描速度随激光功率的增大而降低。在线能量密度为0.25~0.33 J/mm、激光功率为150~250 W、扫描速度为600~800 mm/s的工艺范围内,可获得无欠熔合孔且无微裂纹的高致密度试样。通过降低扫描速度以增大能量密度容易导致微裂纹的产生,而进一步提高激光功率会加剧欠熔合孔和微裂纹的出现。激光粉末床熔融工艺的高冷却速度促使非平衡快速凝固,形成了亚微米级的胞状结构和细小的枝晶结构。
By optimizing the laser powder-bed fusion process parameters,the work aims to fabricate crack-free and highly dense MNiHEA high-temperature high-entropy alloys with no lack-of-fusion porosity,so as to reduce defect rates and enhance mechanical properties,thus providing valuable references for advancing laser powder-bed fusion additive manufacturing processes for high-temperature resistant alloys.With pre-alloyed MNiHEA powder as the raw material,an orthogonal experiment was conducted to design laser power and scanning speed,and both single-track and cubic block samples were subsequently fabricated.Additionally,linear energy density was introduced as a key indicator to systematically investigate the effect of laser power and scanning speed on the cross-sectional geometry and surface topography of single-track molten pools,as well as on the formation of lack-of-fusion pores,microcracks,and the densification behavior in cubic block samples.Subsequently,a comprehensive microstructural analysis was performed on the high-density samples fabricated under the optimized process parameters.When the scanning speed was set at 1600 mm/s,balling phenomenon was observed across the entire laser power range of 100-400 W.As the laser power increased to 200-250 W and 300-400 W,with corresponding scanning speed reducing to 1400 mm/s and 1200 mm/s respectively,the balling effect remained pronounced.Samples free from lack-of-fusion pores and microcracks,with a relative density exceeding 99.9%,were achieved under the combined condition of a linear energy density of 0.25-0.33 J/mm,laser power of 150-250 W,and scanning speed of 600-800 mm/s.The internal pores within the samples primarily consisted of spherical keyhole pores and solidification gas pores.Furthermore,four sets of high-density samples were obtained,whose microstructures exhibited typical"fish-scale"morphology.With the increasing linear energy density,the molten pool depth progressively increased.Both the interior and boundary regions of the molten pools were composed of metastable,micron-scale dislocation cells.High scanning speed is more likely to induce balling phenomenon,and the critical scanning speed for balling decreases with the increasing laser power.Within the process window of linear energy density at 0.25-0.33 J/mm,laser power at 150-250 W,and scanning speed at 600-800 mm/s,high-density samples free from lack-of-fusion pores and microcracks can be obtained.Reducing the scanning speed to increase energy density readily leads to the formation of microcracks,while further increasing the laser power exacerbates the occurrence of both lack-of-fusion pores and microcracks.The high cooling rates inherent to the laser powder-bed fusion process promote non-equilibrium rapid solidification,resulting in the formation of sub-micron cellular structures and fine dendritic features.
作者
伍诗伟
贾岳飞
Hou Yi Chia
郑秋菊
闫文韬
杨守峰
WU Shiwei;JIA Yuefei;Hou Yi Chia;ZHENG Qiuju;YAN Wentao;YANG Shoufeng(Chongqing Institute of Green and Intelligent Technology,Chinese Academy of Sciences,Chongqing 400714,China;State Key Laboratory of Materials for Advanced Nuclear Energy(MANE),Shanghai University,Shanghai 200444,China;Department of Mechanical Engineering,National University of Singapore,Singapore 117575,Singapore)
出处
《精密成形工程》
北大核心
2025年第12期45-53,共9页
Journal of Netshape Forming Engineering
基金
重庆市人才引进计划项目(CSTB2025YCJH-KYXM0001)
重庆市科技局“多材料激光精密增材制造关键技术与装备”项目
国家自然科学基金(52401215,52401214,52201051)
上海市白玉兰人才计划浦江项目(24PJD035)
上海市教育委员会创新计划(2021-01-07-00-09-E00114)
上海市科学技术委员会科技计划项目(25CL2902300)
上海市探索者计划(25TS1401900)。
关键词
增材制造
激光粉末床熔融
抗开裂高温高熵合金
工艺优化
微观组织
additive manufacturing
laser powder-bed fusion
crack-resistant high-temperature high-entropy alloy
process parameter optimization
microstructure
