Year: 2025
Type: article
Abstract: New proposals include the precipitation of new phases and intermetallics in light alloys occur on bifilms rather than on grain boundaries (confusion is understandable because, commonly, it seems that as many as 50 per cent of grain boundaries contain bifilms). The formation and growth on bifilms result from the saving of plastic work to accommodate the volume and shape change of the new phase, which can be orders of magnitude higher than the saving of interfacial energy on grain boundaries. The bifilm, if previously closed, is forced to open by this process, called ‘Precipitation Cleavage’. The term ‘cleavage’ refers to the cleaving open of the bifilm, dispers- ing the volume change elastically over a relatively extensive area. This is the mechanism explain- ing the sensitisation heat treatments for (i) embrittlement, (ii) invasive corrosion as in stress corro- sion cracking, and (iii) invasion of hydrogen into opened bifilms as ‘sinks’, leading to surface blis- tering and hydrogen embrittlement of the matrix. Direct visual evidence is provided by (i) surface blisters during hydrogen charging, and (ii) fracture surfaces displaying quasi cleavage facets, and fisheyes observed in steels and more recently also in light alloys.
Source: Metals
DOI: 10.3390/met15101084
Author: John Campbell
Institution: University of Birmingham
Language: English
Subfield: Metals and Alloys
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W4414611617