Thoughts from NMD-ATM

I spent the beginning of this week in Madras attending NMD-ATM. I made a presentation titled Rafting; are elastic stresses alone sufficient to explain it? in the conference. I attended several interesting talks. Among them, the talk of GF Vander Voort on ASTM E1245 standards and Balamuralikrishnan (of DMRL) on AFM deserve a special mention.

I also liked a talk on by Swe-Kai Chen on, hold your breath, Cu-Ni-Al-Co-Cr-Fe-Ti-Mo alloy series, the so-called high entropy alloys (HEA). Apparently, the elemental alloying sequence in such alloys depends primarily on the melting point and the effects of atomic size and crystal structure are secondary. That makes sense since mechanical alloying was used to produce these alloys, and, we know that mechanical alloying is a result of chemical mixing. The bond strength and hence the melting point thus would play a role in deciding the alloying sequence. That gave rise to the question, namely, whether the alloying sequence would depend on the mechanism used to produce the alloys. In other words, are there methods of preparation where the alloying sequence would be determined by atomic size or crystal structure? For example, would radiation induced alloying produce a different sequence?

At the end of Chen's talk, Prof. BS Murty also indicated that the mechanism behind the alloying sequence selection could be the particle size induced reduction in the melting temperature (which is in turn related to the chemical bonding).