摘要
采用激光选区熔化技术制备了铍铝合金,分析了在低激光功率、高激光功率以及逐层单向线扫描和67°层间交错扫描两种扫描策略下铍铝合金中的成形缺陷、显微组织和硬度。结果表明:铍铝合金中的成形缺陷主要有气孔、微孔、热裂纹和熔合不良。气孔尺寸较小且数量很少,对合金性能影响不大;微孔可以通过采用67°层间交错扫描和提高激光功率的方式消除;热裂纹主要是由熔池凝固末期熔池中心的柱状组织间长通道中液膜受其周围前一层熔池的拉应力引起,并在后期逐层沉积过程外延生长扩展,热裂纹的开口宽度随着能量密度增加而增大;熔合不良是熔池被周围新扫描熔池高搭接率重熔时受多次热循环影响,其边缘铍铝两相扩散向稳态转变,铍相枝晶长大和铝相扩散引起显微空隙所致。增材制造铍铝合金的显微组织中主要包含铝相、铍相和一部分亚稳态组织,其中铍相与亚稳态组织共同引起合金中较大的残余应力;合金中铍相基面(0001)取向虽然有一定的择优分布,但也表现出随机性,铝相(100)方向沿熔池扫描方向则存在明显的择优取向,使合金组织呈现各向异性。另外,通过沿熔池扫描方向测试硬度得知,铍铝合金因组织细小及存在大量的亚稳态组织而表现出更高的显微硬度。
Be-Al alloy was prepared by laser selective melting.The forming defects,microstructure,and hardness of the Be-Al alloy were analyzed under low or high laser power with two scanning strategies of layer by layer unidirectional line scanning and 67°interlayer staggered scanning.The results show that the primary forming defects in the Be-Al alloy include pores,micropores,hot cracks,and poor fusion.The pores are small in size and few in number,thus having little effect on the properties of the alloy.The micropores can be eliminated by using the 67°interlayer staggered scanning and increasing the laser power.The hot cracks are mainly caused by the tensile stress exerted on the liquid film in the long channels between the columnar structures at the center of the molten pool at the end of solidification,extending in the subsequent layer-by-layer deposition process.And the opening width of the hot cracks increases with the increase of energy density.The molten pool is affected by multiple thermal cycles when it is remelted by the surrounding newly scanned molten pool with a high lap rate,leading to a steady-state transition of Be-Al two-phase diffusion,dendrite growth of Be phase,and difussion of Al phase to cause microvoids that result in poor fusion.The microstructure of the Be-Al alloy prepared by additive manufacturing mainly consists of Al phase,Be phase,and some metastable microstructure,in which the Be phase and metastable microstructure collectively cause a significant residual stress in the alloy.Additionally,while the orientation of the Be phase base plane(0001)in the alloy has a certain preferential distribution,it also exhibits randomness.In contrast,the direction of Al phase(100)has an obvious preferential orientation along the scanning direction of the molten pool,resulting in the anisotropy of the alloy microstructure.Meanwhile,the hardness test along the scanning direction of the molten pool reveals that the Be-Al alloy exhibits higher microhardness due to its fine microstructure and a large number of me
作者
代彦明
谢垚
王东新
李军义
张鹏
李春生
张健康
DAI Yan-ming;XIE Yao;WANG Dong-xin;LI Jun-yi;ZHANG Peng;LI Chun-sheng;ZHANG Jian-kang(National Key Laboratory of Rare Metal Special Materials,Northwest Institute of Rare Metal Materials Ningxia Co.,Ltd.,Shizuishan 753000,China;Key Laboratory of Advanced F unctional Materials,Education Ministry of China,College of Materials Science and Engineering,Beijing University of Technology,Beijing 100124,China)
出处
《稀有金属与硬质合金》
CAS
CSCD
北大核心
2024年第4期69-77,共9页
Rare Metals and Cemented Carbides
基金
国家重点研发计划(2021YFC2902304)
宁夏自然科学基金(2023AAC03893)
中央企业高端金属材料创新联合体项目(2023)。
关键词
激光选区熔化
铍铝合金
缺陷
激光功率
层间交错扫描
laser selective melting
Be-Al alloy
defect
laser power
interlayer staggered scanning
