The Future Engineer podcast engineer

STEM XX 016 episode is on the importance of multidisciplinary engineering, the power of positive thinking and biomimetics – learning from nature to solve our technical problems.

If you have ~30min to spare, have a listen and please leave comments below and tell me what you think. Thanks!

You can download it here to listen.

Inorganic PCAs for a low-cost 3D printed Ti-Nb alloy

This new study from the Multifunctional Materials Manufacturing Lab has been led by James Borgman, MMM Lab alumnus, and is on ‘The Use of Inorganic Process Control Agents to Mill Titanium-Niobium Powders Suitable for the Selective Laser Melting Process‘. It has been published in the Powder Technology Elsevier Journal.

The alloying of Ti with Nb produces low-stiffness alloys, which is of interest for us because we are developing new alloys with lower stiffness, as close as possible to that of bone. These alloys can then be used in the manufacture of orthopaedic implants.

3D printed alloys typically require the feedstock of powder to be prealloyed, so the chemical homogeneity of the final part is achieved. Furthermore, this feedstock needs to have a certain level of flowability. Otherwise the wiper of the 3D printer (an SLM machine in our case) cannot spread an even and fine layer of powder, and in this way prevent any defect or void in the final samples.

Prealloying tends to be a significant hurdle in this process: it is very costly and energy demanding. The equipment needed to do this operation is big and expensive to run. Only the running of large batches can be justified financially. That is why gas atomisation (a typical pre-alloying process) companies only offer mainstream alloys in the Products Catalogue. If the alloy under study is bespoke and unique, it is difficult to obtain atomised alloys.

In this study we have investigated how a traditional, well-understood and low-cost method such as Ball Milling can be used for the prealloying of regular shaped powders of alloy. One of the most important parameters in this operation is the addition of the PCA (the process control agent), which facilitates the alloying process in the solid state. But the selection of this PCA needs to be judicious, since the PCA can contaminate the alloy powder with undesirable elements (e.g. C or N) that spoils the 3D printed alloy’s mechanical properties.

We have offered as a solution the use of Ca and Sn, and compared it to the results obtained with a typical PCA such as Stearic Acid.

Both inorganic elements were effective, especially the Ca, which opens a new door to the use of PCAs that can also provide biological properties to the alloys, since Ca is biodegradable.

You can read the full paper here: DOI: 10.1016/j.powtec.2022.117546.

This work was also presented at the EuroPM 2021. You can read it here.

Rapid measurement of elastic properties in polymeric foams

Our work on characterising polymeric foams in-situ, without destructive sample collection and tedious sample preparation has been published in Materials Letters.

Sponsored by the Innovate UK under their IDP 14 programme, this study correlates the results from an Ultrasonic technique to the more traditional quasi-static Universal Testing Machine approach, and in this way manufacturers and quality control personnel can assess the material before it has left the production line.

“Comparison of elastic properties of low-density polymeric foams determined by ultrasonic wave propagation and quasi-static mechanical testing“, Materials Letters, Volume 263, 15 March 2020, 127243, https://doi.org/10.1016/j.matlet.2019.127243

A novel in-situ in-line testing approach to polymeric foams properties, it can be deployed to production lines for rapid quality control without the inconvenience of sample preparation and tedious mechanical test on coupons.