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Thermionic electron emission, the release of charged particles from a hot body, was first observed more than 170 years ago and theorised more than 120 years ago. Yet this important electron–matter interaction has been overlooked in modern electron-beam powder-bed fusion systems.

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I have shown that thermionic electron emission can be nicely captured and used as an effective medium for process monitoring, an approach named as In-Melt Electron Analysis (IMEA). The information it carries includes, among other things, the temperature field, melt-pool dynamics, and process anomalies (). Beyond this, the physical transformations of matter during electron-beam interaction such as heating, oxide evaporation, melting, and spattering, are also clearly reflected in the IMEA signal ().

Producing crack-free nickel-based superalloys by additive manufacturing is challenging: these alloys are susceptible to hot cracking, and their cracking susceptibility is difficult to quantify. To address this, I developed a two-parameter Heat-Resistance–Deformation-Resistance (HR–DR) model. By relating chemical composition (both major and minor elements) to cracking susceptibility, the HR–DR model offers a practical tool for alloy development. Related reading: , ,

Post-processing can enhance mechanical properties, but it is not always safe. Because the gamma-prime phase forms early and rapidly, superalloys become prone to a macroscopic, catastrophic form of failure known as strain-age cracking. In-situ monitoring confirms that achieving post-processing free of macroscopic cracking is, unfortunately, far from straightforward. Related reading:

Post-additive-manufacturing processing tailors the grain structure: the evolution of crystallographic texture can be tracked by neutron diffraction (). Designing this crystalline arrangement is critical, because grain-boundary sliding is a common operative deformation mode at elevated temperature (). The resulting mechanical properties can be further tuned through the size and morphology of the strengthening precipitates (; ).