Abstract

There has been significant development in metal additive manufacturing (MAM) technology over the past few
decades, and considerable progress has been made in understanding how various processes and their parameters
influence the properties of printed metallic parts. Despite this, the knowledge concerning its characteristics has
been dispersed across a variety of publications and sources, making it difficult to gain a comprehensive understanding
of the entire field, especially for businesses interested in additive manufacturing (AM). In order to
bridge this gap, periodic reviews encompassing state-of-the-art as the whole are necessary. Therefore, this article
provides a comprehensive overview of the essential features of MAM techniques based on the most recent scientific
knowledge. It explores emerging research on four of the most significant technologies, including material
extrusion (ME), binder jetting (BJ), powder bed fusion (PBF), and directed energy deposition (DED). As well as
providing an outline of fundamental process characteristics, ongoing efforts to optimize them and current
challenges, it also highlights gaps in understanding and future research and development needs. A significant
feature of this review is the provision of substantial documentation regarding the mechanical properties of
materials processed by a variety of commercial systems, including a variety of novel hybrid additive
manufacturing (HAM) machines. This is accompanied by an investigation into the most recent works done to
characterize the environmental impact along with a conceptual framework for improving the energy efficiency
(EE) of the manufacturing process. As a result of reporting on both the characteristics of several MAM processes
along with their sustainability features in one integrated article, it is anticipated that this information will serve
as a valuable resource for both the academic and manufacturing communities to better appreciate and understand
what differentiates MAM from traditional manufacturing (TM) processes, thus facilitating its future
advancement and adoption.