An approach to powder feedstock modification for in-situ alloying in metal additive manufacture to improve the processability of difficult-to-process materials using carbon nanotubes
Metal additive manufacturing using laser-based techniques is receiving substantial attention from the academic and industrial sectors as it offers unmatched degrees of freedom that enable the fabrication of highly complex structures, not achievable otherwise. This is complimented by the characteristic microstructures produced by the high thermal gradients associated with these processes that yield parts exhibiting superior mechanical properties, depending on the material system used. Although readily-available alloys are commonly utilised, developing new alloys specifically tailored for the process is a growing field of research.
One of the motives behind developing new alloys specific to the process is that readily-available ones are not necessarily designed with the process requirements in mind, such as the nature of the laser-material interaction and the response of the material to rapid solidification (amongst others). Considering the case of laser powder bed fusion (L-PBF) of Al and its alloys, the main challenge is the material’s high reflectivity and low laser absorptivity in the range of wavelength used in these processes. Therefore, L-PBF of Al has always focussed on alloys (AlSi10Mg, AA-7075, Scalmalloy … etc) since attempts to process pure Al have been unsuccessful.
In this work, we proposed and validated a novel approach to overcome the challenges of processing highly reflective materials within L-PBF through its augmentation with another material that improves its laser absorptivity. Though we choose to demonstrate this approach to the Al-MWCNT system, its transferability to other material systems opens up a wide range of exciting opportunities. For this study, we investigated the process-structure-property relationship in the Al-MWCNT composite prepared by high energy ball milling followed by SLM. The properties of these composites largely depend on the method of fabrication used since it dictates the interfaces between the matrix and reinforcement, as well as the interfacial reactions, if any. Besides presenting and validating this novel approach, we also meticulously studied, in a holistic investigation, the effect of laser processing on MWCNT and its interaction with the matrix within the complex melting and solidification profiles imposed. This was undertaken using a range of analytical and experimental techniques to elucidate a comprehensive understanding of the metallurgical and mechanical properties of the produced material, which was then also correlated to the manufacturing process.
This study used pure Al reinforced with MWCNT for processing by L-PBF with the aim of developing a new approach to improve materials’ processability. Furthermore, it is the first in-depth study on the influence of L-PBF processing on MWCNT-reinforced composites. Therefore, it presents a significant contribution to the existing knowledge regarding the response of such composite material to laser irradiation in L-PBF as well as the interfacial reactions between the matrix and the reinforcement.
Dr. N. Aboulkhair
Anne Mclaren Fellowship, Faculty of Engineering
University of Nottingham
Jubilee Campus
Wollaton Road
Nottingham NG8 1BB
UK
| Phone | +44 115 951 5151 switchboard |
| Dr. N. Aboulkhair | |
| Http | Dr. N. Aboulkhair |
| Centre for Additive Manufacturing, Nottingham University | |
| Nottingham University |