Solidification microstructure and tensile deformation mechanisms of selective electron beam melted Ni3Al-based alloy at room and elevated temperatures

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:802

Article

Yao, Y.¹  Xing, C.¹  Peng, H.²  Guo, H.²  Chen, B.³ 

[1] Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China

[2] Beihang Univ, Key Lab High Temp Struct Mat & Coatings Technol, Minist Ind & Informat Technol, 37 Xueyuan Rd, Beijing 100191, Peoples R China

[3] Univ Leicester, Sch Engn, Leicester LE1 7RH, Leics, England

关键词: Solidification cracking;    Grain boundary;    Dislocation;    Selective electron beam melting;    Additive manufacturing;    Ni-base superalloys;   

DOI  :  10.1016/j.msea.2020.140629

来源: Elsevier

【 摘 要 】

Selective electron beam melting (SEBM) was used to process crack-free Ni3Al-based IC21 alloy (low density superalloy) containing similar to 85% gamma'-volume fraction. There are distinct differences between dendrites and inter-dendritic regions with the presence of coarse gamma+gamma' eutectic and secondary solidification microconstituents (Cr and Mo-rich) in the latter. The pronounced inter-dendritic eutectic regions suggest that a significant elemental partitioning between the liquid and solid occurred during the SEBM. The terminal liquid is trapped at boundaries between dendrites and grains, as evidenced by the liquid films on cracked surfaces. In contrast to extensive studies indicating the segregation of Zr and B, we show unambiguously the segregation of Si to low melting point liquid films and thereby enhancing the susceptibility to solidification cracking in IC21 produced by SEBM. The tensile specimens extracted from the crack-free IC21 samples exhibit superior properties at room temperature (RT) and 1000 degrees C. The RT deformation mechanism is characterised by cutting gamma'-phase with two paired dislocations and antiphase boundaries in between. At 1000 degrees C tensile deformation, the well-developed gamma/gamma' interfacial dislocation networks are in good agreement with their promising high-temperature performance (sigma(y) = 518 +/- 10 MPa, sigma(UTS) = 560 +/- 16 MPa, 20.5% for ductility).

【 授权许可】

Free