材料科学
等轴晶
微观结构
热等静压
选择性激光熔化
高温合金
合金
碳化物
均质化(气候)
复合材料
纹理(宇宙学)
冶金
衍射仪
扫描电子显微镜
生物多样性
人工智能
图像(数学)
生物
计算机科学
生态学
作者
Ahmad Mostafa,Ignacio Picazo Rubio,Vladimir Braïlovski,Mohammad Jahazi,Mamoun Medraj
出处
期刊:Metals
[Multidisciplinary Digital Publishing Institute]
日期:2017-05-30
卷期号:7 (6): 196-196
被引量:213
摘要
3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 °C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 °C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ″-phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb0.78Ti0.22)C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.
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