Selective Laser Melting of Aluminum and Its Alloys

Abstract

The laser-based powder bed fusion (LBPF) process or commonly known as selective laser melting (SLM) has made significant progress since its inception. Initially, conventional materials like 316L, Ti6Al4V, and IN-718 were fabricated using the SLM process. However, it was inevitable to explore the possible fabrication of the second most popular structural material after Fe-based alloys/steel, the Al-based alloys by SLM. Al-based alloys exhibit some inherent difficulties due to the following factors: the presence of surface oxide layer, solidification cracking during melt cooling, high reflectivity from the surface, the high thermal conductivity of the metal, poor flowability of the powder, low melting temperature, etc. Researchers have overcome these difficulties to successfully fabricate the different Al-based alloys by SLM. However, there exists no review dealing with the fabrication of different Al-based alloys by SLM, their fabrication issues, microstructure, and their correlation with properties in detail. Hence, the present review attempts to introduce the SLM process followed by a detailed discussion about the processing parameters that form the core of the alloy development process. This is followed by the current research status on the processing of Al-based alloys and microstructure evaluation (including defects, internal stresses, etc.), which are dealt with on the basis of individual Al-based series. The mechanical properties of these alloys are discussed in detail followed by the other important properties like tribological properties, fatigue properties, etc. Lastly, an outlook is given at the end of this review.

Additive Manufacturing of Aluminum‐Based Metal Matrix Composites—A Review

“…The details on PBF-L and DED-L processes can be found in other reports. [68][69][70] As with lasers, electron beams also make a high energy density beam, but the difference between them is that electron beams use electrons instead of photons. [71] Different from PBF-L, PBF-EB procedure happens in a vacuum chamber (<1 Â 10 À4 mbar) which provides a high purity environment, which can help metals melt in an environment with minimal contamination by oxygen and nitrogen or hydrogen existing in the air or moisture.…”

Investigation on the Microstructure and Mechanical Properties of CNTs-AlSi10Mg Composites Fabricated by Selective Laser Melting

“…Selective laser melting (SLM) is a laser additive manufacturing technology (AM), which uses laser beam to melt metal powders along a given path quickly and completely. Because of its rapid prototyping ability, SLM is widely used in the production of various metals and alloys [ 11 , 12 , 13 , 14 ]. It has the following advantages: capable of producing complex-shaped three-dimensional parts [ 15 ], reducing manufactured time and cost [ 16 ], flexible alloy design [ 17 ], and superior mechanical properties [ 18 ].…”

Effect of Substrate Plate Heating on the Microstructure and Properties of Selective Laser Melted Al-20Si-5Fe-3Cu-1Mg Alloy

“…In addition, high heating and cooling rates that lead to significant thermal gradients around the melt pool may cause undesirable levels of cracking. In general, the problems associated with the fabrication of Al and its alloys by SLM are: (a) oxidation of the surface of the metal powder; (b) obstructed flowability of the powder; (c) low absorptivity of the laser beam and high reflectivity; (d) high thermal conductivity and, hence, wider melt pools placing restrictions on the size of the smallest features in the part that can be fabricated; (e) high solidification shrinkage (may lead to cracking); and (f) high viscosity of the melt [ 36 ]. Such difficulties may result in undesirable microstructures resulting in poor properties of SLM parts.…”

“…Such difficulties may result in undesirable microstructures resulting in poor properties of SLM parts. In addition, Al and its alloys may face other problems such as (a) porosity—improper processing parameters; (b) balling due to too high-energy input; (c) formation of a distorted layer due to too high-energy input and/or with the presence of brittle parts; (d) increased cracking tendency due to the brittle nature of the processing material; (e) high surface roughness of parts because of coarse powder and/or too high energy input; (f) loss of alloying elements, especially when the alloy contains elements with low boiling points and vapor pressures that can be lost during the SLM process; and (g) poor dimensional accuracy due to the presence of oxide layers, where the energy input has to be increased unprecedentedly [ 36 , 37 , 38 ].…”