Epitaxy and Microstructure Evolution in Metal Additive Manufacturing

Abstract

Metal additive manufacturing (AM) works on the principle of incremental layer-by-layer material consolidation, facilitating the fabrication of objects of arbitrary complexity through the controlled melting and resolidification of feedstock materials by using high-power energy sources. The focus of metal AM is to produce complex-shaped components made of metals and alloys to meet demands from various industrial sectors such as defense, aerospace, automotive, and biomedicine. Metal AM involves a complex interplay between multiple modes of energy and mass transfer, fluid flow, phase change, and microstructural evolution. Understanding the fundamental physics of these phenomena is a key requirement for metal AM process development and optimization. The effects of material characteristics and processing conditions on the resulting epitaxy and microstructure are of critical interest in metal AM. This article reviews various metal AM processes in the context of fabricating metal and alloy parts through epitaxial solidification, with material systems ranging from pure-metal and prealloyed to multicomponent materials. The aim is to cover the relationships between various AM processes and the resulting microstructures in these material systems.

Metallic materials for 3D printing

“…18 LS is a powder bed fusion 19 technique in which a scanning laser is used to consolidate sequentially deposited layers of a metal powder. Different types of lasers including CO 2 , disk, Nd:YAG, and fi ber lasers are used.…”

Modeling of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions

“…[91] They are often roughly estimated; for example, [90] used ΔT N = 5 K, ΔT = 0.5 K, and N max = 10 12 m −3 for Al-3 wt pct Cu. [92] used a Gaussian distribution for both surface and volume nucleation of Al-7 wt pct Si, placing ΔT N at 10 K. Experimental observations by Basak and Das [93] estimated ΔT N to be near 0.2 ΔT m in a pure metal. In the present calculations, the ΔT N and ΔT σ values from Boettinger [91] and N max of 5 9 10 12 m −3 were used.…”

“…Nucleation at the small length scale of these structures did not occur in the model. Growth of both cells and dendrites under AM conditions has been observed experimentally, [93] and the transition from dendrites to cells at fast cooling rates has been modeled via CA previously. [46] C.…”

Additive Manufacturing of Nickel‐Base Superalloy René N5 through Scanning Laser Epitaxy (SLE) − Material Processing, Microstructures, and Microhardness Properties

“…[12] Superalloy components may be repaired using different welding processes such as gas tungsten arc (GTA) welding or tungsten inert gas (TIG) welding, electron beam (EB) welding, and laser welding. [14] Epitaxial laser metal forming (ELMF) was the first AM process to demonstrate the formation of multiple SX layers of CMSX-4 [7] Achieving SX microstructure through additive manufacturing (AM)-based processes is challenging.…”

“…Thus, a limited amount of literature is available on the repair of SX components. [14] Epitaxial laser metal forming (ELMF) was the first AM process to demonstrate the formation of multiple SX layers of CMSX-4…”