There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Additive manufacturing of metallic components – Process, structure and properties

Additive manufacturing of metals

Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.

The metallurgy and processing science of metal additive manufacturing

/pdf/erratum-to-strategy-for-texture-management-in-metals-389w30k60t.pdf

Erratum to: Strategy for Texture Management in Metals Additive Manufacturing

http://manuscript.elsevier.com/S0749641921002436/pdf/S0749641921002436.pdf

Creep anisotropy modeling and uncertainty quantification of an additively manufactured Ni-based superalloy

We review the progress of additive manufacturing effort on refractory metal tungsten and tungsten alloys. These materials are excellent candidates for a variety of high temperature applications but extremely challenging to fabricate via additive manufacturing due to a series of existing issues during the manufacturing. We outline these issues and discuss the current understanding and progress to tackle them. Laser powder-bed-fusion, laser directed-energy-deposition, and electron beam powder-bed-fusion are three common techniques that have been applied to additively manufacture pure tungsten. This overview discusses current observations and understanding on the issues associated with each of these techniques. We identify future research opportunities in additive manufacturing of refractory metals. 

A review on additive manufacturing of refractory tungsten and tungsten alloys

Additive manufacturing processes are becoming increasingly utilized throughout industry. These technologies enable novel design and manufacture of complex components, reduce material waste streams, and potentially reduce development cycles via rapid prototyping. The high-\(\gamma ^{'}\) Ni-base superalloys are of particular interest to the gas turbine engine industry due their high-temperature resistance. However, as a result of the high \(\gamma ^{'}\) volume fraction, these alloys are traditionally termed non-weldable due to a propensity to crack during welding from a host of mechanisms including hot-tearing and strain-age cracking. These mechanisms are subsequently found in fusion-based additive manufacturing processes. Furthermore, there is a long history of employing traditionally processed components in gas turbine engines, and hence, the performance of materials produced by additive manufacturing needs to be closely investigated. In this work is presented the tensile, high-temperature fatigue, and creep deformation behavior for Inconel 738 fabricated through electron beam melting (EBM) additive manufacturing. Under tensile and fatigue conditions, the material was observed to perform in an isotropic manner when tested parallel and transverse to the build direction. Although under creep conditions, the material exhibited an anisotropy between material tested parallel and transverse to the build direction. With the difference attributed to the fine columnar grain structure observed in the additively manufactured Inconel 738. Ultimately, the EBM material was observed to perform comparably to the conventional cast Inconel 738.

Michael M. Kirka

Papers

Erratum to: Strategy for Texture Management in Metals Additive Manufacturing

Creep anisotropy modeling and uncertainty quantification of an additively manufactured Ni-based superalloy

A review on additive manufacturing of refractory tungsten and tungsten alloys

Mechanical Performance of a Non-weldable Ni-Base Superalloy: Inconel 738 Fabricated by Electron Beam Melting

Microstructure Evolution and Tensile Properties of a Selectively Laser Melted CoNi-Base Superalloy