On the compressibility of metal powders

ABSTRACT

A new equation relating the porosity of green compacts and the applied external pressure during the cold die compaction of metal powders is proposed. All of the parameters in the model have a clear physical meaning. These parameters are those related to the plastic behaviour of the material, as well as to the ‘structural resistance’ of the powder mass. Also the friction between the powders and die walls is considered, as a kind of constraint that diminishes the local pressure borne by the fully dense material. The model includes, as a key parameter, the tap porosity of the powders (an extremely useful property that contains the morphometric information of the powder). The proposed model has been experimentally checked with the compressibility curves obtained with five metal powders of different types. The agreement between the model and experimental data is reasonable over the tested pressure range.

KEYWORDS:

• Metals
• powder processing modelling
• cold die compaction

Acknowledgements

The authors also wish to thank the technicians J. Pinto, M. Madrid and M. Sanchez for experimental assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Dr J. M. Montes is a Professor in the Department of Materials Science and Engineering at the University of Seville (Spain). He has published more than 50 works in the form of articles, and a number of book chapters and conference proceedings. His research areas include powder metallurgy, porous materials modelling, electrical consolidation techniques, and nanostructured materials obtained by mechanical milling. He is a co-author of the textbook “Ciencia e IngenierÃa de los Materiales” (in Spanish).

Dr F. G. Cuevas started his career in Materials Science at the University of Sevilla, moving ten years ago to his actual destination as a Lecturer in the Department of Chemical Engineering and Materials Science at the University of Huelva (Spain). With more than 50 works in the form of articles, and several book chapters and conference proceedings, his research areas in the field of powder metallurgy include mechanical alloying, porous materials modelling and electrical consolidation techniques.

Dr J. Cintas is a Professor in the Higher Technical School of Engineering at the University of Seville. His research areas include powder metallurgy, mechanosynthesis, nanostructured and amorphous materials, and electrical sintering techniques.

Dr F. Ternero is an Assistant Lecturer in the Department of Materials Science and Engineering at the University of Seville (Spain). She started her formation in the Institute of Materials Science (CSIC-Spain), finishing her PhD studies in 2013. With several published articles, her research areas include metallic nanoparticles and metallic nanomaterials, powder metallurgy, electrical consolidation techniques, and nanostructured materials obtained by mechanical milling.

Dr E.S. Caballero is an Assistant Lecturer in the Department of Materials Science and Engineering at the University of Seville (Spain). Trained as a Materials Engineer and a Physics Graduate, he completed his PhD dissertation in 2014. He has published several works in the form of articles. His research areas include AMCs, powder metallurgy, nanostructured materials and electrical consolidation techniques.

ORCID

J.M. Montes http://orcid.org/0000-0002-4103-6291

F.G. Cuevas http://orcid.org/0000-0002-1167-1569

J. Cintas http://orcid.org/0000-0002-6661-916X

F. Ternero http://orcid.org/0000-0002-9818-1473

E.S. Caballero http://orcid.org/0000-0002-3188-1731

Additional information

Funding

The authors are grateful to FEDER/MCyT, Madrid, for funding this research within the framework of Projects DPI2015-69550-C2-1-P and DPI2015-69550-C2-2-P.