In-situ X-ray computed tomography tensile tests and analysis of damage mechanism and mechanical properties in laser powder b e d fused Invar 36 alloy  

作　　者：Qidong Yang Shuo Yang Shiyu Ma Junhan Zhou Ye Zhou Rongzheng Huang Kai Wei Zhaoliang Qu Xujing Yang 

机构地区：[1]Key Laboratory of Advanced Design and Simulation Techniques for Special Equipment,Ministry of Education,Hunan University,Changsha 410082,China [2]Institute of Advanced Structure Technology,Beijing Institute of Technology,Beijing 100081,China [3]State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,Changsha 410083,China

出　　处：《Journal of Materials Science & Technology》2024年第8期29-46,共18页材料科学技术（英文版）

基　　金：support of the National Natural Science Foundation of China(Grant Nos.12372133 and 12027901);supported by the Natural Science Foun-dation of Hunan Province(Grant No.2021JJ30085);the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC30306);Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University(Grant No.Kfkt2021-01);the Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant No.52175012).

摘　　要：Laser powder bed fusion(LPBF)is a potential additive manufacturing process to manufacture Invar 36 alloy components with complicated geometry.Whereas it inevitably introduces specific microstructures and pore defects,which will further influence the mechanical properties.Hence,aiming at exploring the LPBF process-related microstructures and pore defects,and especially their influences on the damage mechanism and mechanical properties,Invar 36 alloy was manufactured by LPBF under designed different laser scanning speeds.The microstructure observations reveal that higher scanning speeds lead to equiaxed and short columnar grains with higher dislocation density,while lower scanning speeds result in elongated columnar grains with lower dislocation density.The pore defects analyzed by X-ray computed tomography(XCT)suggest that the high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion(LOF)pores,and the excessively low laser scanning speed produces relatively small keyhole pores with high sphericity.Moreover,the insitu XCT tensile tests were originally performed to evaluate the damage evolution and failure mechanism.Specifically,high laser scanning speed causes brittle fracture due to the rapid growth and coalescence of initial lamellar LOF pores along the scan-ning direction.Low laser scanning speed induces ductile fracture originating from unstable depressions in the surfaces,while metallurgical and keyhole pores have little impact on damage evolution.Eventually,the process-structure-property correlation is established.The presence of high volume fraction of lamel-lar LOF pores,resulting from high scanning speed,leads to inferior yield strength and ductility.Besides,specimens without LOF pores exhibit larger grain sizes and lower dislocation density at decreased scanning speeds,slightly reducing yield strength while slightly enhancing ductility.This understanding lays the foundation for widespread applications of LPBF-processed Invar 36 alloy.

关 键 词：Invar 36 alloy Laser powder bed fusion Microstructure Pore defects Mechanical property X-ray tomography in-situ tensile test 

分 类 号：TG142[一般工业技术—材料科学与工程]