scholarly journals Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718

2020 ◽  
Vol 106 (7-8) ◽  
pp. 3597-3607 ◽  
Author(s):  
P. Karimi ◽  
E. Sadeghi ◽  
J. Ålgårdh ◽  
P. Harlin ◽  
J. Andersson
Keyword(s):  
Corrosion Behavior ◽  
Functional Performance ◽  
Great Promise ◽  
Alloy 718 ◽  
Microstructural Characteristics ◽  
Powder Bed ◽  
Part Geometry ◽  
History Of ◽  
Exterior Regions ◽  
Metallic Parts

AbstractElectron beam-powder bed fusion (EB-PBF), a high-temperature additive manufacturing (AM) technique, shows great promise in the production of high-quality metallic parts in different applications such as the aerospace industry. To achieve a higher build efficiency, it is ideal to build multiple parts together with as low spacing as possible between the respective parts. In the EB-PBF technique, there are many unknown variations in microstructural characteristics and functional performance that could be induced as a result of the location of the parts on the build plate, gaps between the parts and part geometry, etc. In the present study, the variations in the microstructure and corrosion performance as a function of the parts location on the build plate in the EB-PBF process were investigated. The microstructural features were correlated with the thermal history of the samples built in different locations on the build plate, including exterior (the outermost), middle (between the outermost and innermost), and interior (the innermost) regions. The cubic coupons located in the exterior regions showed increased level (~ 20 %) of defects (mainly in the form of shrinkage pores) and lower level (~ 30-35 %) of Nb-rich phase fraction due to their higher cooling rates compared to the interior and middle samples. Electrochemical investigations showed that the location indirectly had a substantial influence on the corrosion behavior, verified by a significant increase in polarization resistance (Rp) from the exterior (2.1 ± 0.3 kΩ.cm2) to interior regions (39.2 ± 4.1 kΩ.cm2).

Scalable Thermal Simulation of Powder Bed Fusion

2021 ◽  
pp. 1-17
Author(s):  
Yaqi Zhang ◽  
Vadim Shapiro ◽  
Paul Witherell
Keyword(s):  
Spatial Data ◽  
Manufacturing Process ◽  
Thermal Simulation ◽  
Powder Bed Fusion ◽  
Time Step ◽  
Powder Bed ◽  
Melt Pool ◽  
Scan Path ◽  
History Of ◽  
Metallic Parts

Abstract Powder bed fusion (PBF) has become a widely used additive manufacturing technology to produce metallic parts. In PBF, thermal field evolution during the manufacturing process plays an important role in determining both geometric and mechanical properties of the fabricated parts. Thermal simulation of the PBF process is computationally challenging due to the geometric complexity of the manufacturing process and the inherent computational complexity that requires a numerical solution at every time increment of the process. We propose a new thermal simulation of the PBF process based on the laser scan path. Our approach is unique in that it simulates the thermal history of the process on the discretization of the geometry implied by the process plan, as opposed to voxelization or meshing of the design geometry. The discretization is based on the laser scan path, and the thermal model is formulated directly in terms of the manufacturing primitives. An element growth mechanism is introduced to simulate the evolution of the melt pool during the manufacturing process. A spatial data structure, called contact graph, is used to represent the discretized domain and capture all thermal interactions. The simulation is localized through exploiting spatial and temporal locality. This limits the need to update to at most a constant number of elements at each time step, which implies that the proposed simulation not only scales to handle 3D components of arbitrary complexity but also can achieve real-time performance. The simulation is fully implemented and validated against experimental data and other simulation results.

scholarly journals Oxygen balance during laser powder bed fusion of Alloy 718

2021 ◽  
Vol 201 ◽  
pp. 109511
Author(s):  
Camille Pauzon ◽  
Ahmad Raza ◽  
Eduard Hryha ◽  
Pierre Forêt
Keyword(s):  
Oxygen Balance ◽  
Powder Bed Fusion ◽  
Alloy 718 ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

scholarly journals The creep behaviour of nickel alloy 718 manufactured by laser powder bed fusion

2021 ◽  
Vol 204 ◽  
pp. 109647
Author(s):  
S. Sanchez ◽  
G. Gaspard ◽  
C.J. Hyde ◽  
I.A. Ashcroft ◽  
Ravi G.A. ◽  
...  
Keyword(s):  
Nickel Alloy ◽  
Creep Behaviour ◽  
Powder Bed Fusion ◽  
Alloy 718 ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

OUR CHALLENGES FOR THE 70'S President's Address, 1970

PEDIATRICS ◽  
1971 ◽  
Vol 47 (2) ◽  
pp. 465-469
Author(s):  
Russell W. Mapes
Keyword(s):  
American Academy ◽  
General Medicine ◽  
Vice President ◽  
Medical Community ◽  
Great Promise ◽  
Quality Health Care ◽  
American Academy Of Pediatrics ◽  
Quality Health ◽  
History Of ◽  
Organized Medicine

For any national organization striving to keep pace with increasingly diverse responsibilities and objectives, there are appropriate times when that organization must pause, reflect, and project before moving forward to meet the goals to which it has dedicated its programs and priorities. This year marks the 40th anniversary of the American Academy of Pediatrics. It was June 23, 1930 that 35 pediatricians met in Harper Hospital in Detroit to establish the Academy as the organization to speak for the interests and health of children, as well as the interests of its pediatric members. This year also marks the beginning of a new decade, a decade which holds great promise for the future of pediatrics but a decade which also presents significant challenges which we must meet if we are to deliver quality health care to all children. The American Academy of Pediatrics is indeed fortunate to be able to draw from the accomplishments of a progressive history of achievement, distinguished by the vision of its early founders. In the 1920's the medical community widely predicted that pediatrics was disappearing as a specialty, that in a few years it would merge into the field of general medicine. Concern was also expressed that pediatrics was not sufficiently represented in the echelons of organized medicine and, consequently, the cause of child health was not being served adequately. To pediatricians like Isaac A. Abt, the first president of the Academy, to John L. Morse, its first vice-president, and to Clifford G. Grulee, the Academy's pioneering executive director, these were very real challenges, but they were not causes for pessimism or defeatism.

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