Hard second phases in alloys and composites

Probing at the Nanoscale the Structure and Properties of Hard Second Phases in Alloys and Composites

Lionel Michelet, Marta Fornabaio and Andreas Mortensen with former contributions from Vaclav Pejchal, Martin Mueller, Aparna Singh, Goran Zagar, Andreas Rossoll, Cyril Dénéréaz, Raphael Charvet  

Our ambition in this new project funded by an ERC Advanced Grant is to probe the strength of “second” phases in multiphase metal alloys and composites, meaning of hard particles added to strengthen a metal, or alternatively of brittle inclusions that weaken it. Such phases are ubiquitous in structural metals; yet not much is known of the microstructural features that govern their strength.

The underlying hypothesis of this project is that defects that limit the strength of such hard second phases can be identified and then altered by processing. Operationally, we plan to apply and extend nanomechanical testing to probe the strength of micrometric, irregularly shaped, hard particles currently used to strengthen metals. We aim to test such particles whole, and also for their local internal properties. Testing will rely on focused ion beam machining combined with nanoindentation and original testing procedures, to access local and global strength values for hard second phase particles. Materials systems to be investigated are: (i) ceramic particles for the reinforcement of metal composites; (ii) silicon in aluminium, (iii) cementite and MC carbides in steel. Defects limiting the strength of these hard brittle phases suggested by mechanical testing are to be identified by means of microstructural characterization, electron microscopy notably, of both virgin and tested particles.




For more information please refer to:


Processing and micro-mechanical characterization of multi-component transition MC carbides in iron

L. Deillon; M. Fornabaio; G. Zagar; L. Michelet; A. Mortensen 

Journal of the European Ceramic Society. 2021-03-06. Vol. 41, num. 7, p. 3937-3946. DOI : 10.1016/j.jeurceramsoc.2021.02.044.

On the diametric compression strength test of brittle spherical particles

G. Zagar; V. Pejchal; M. Kissling; A. Mortensen 

European Journal Of Mechanics A-Solids. 2018-11-01. Vol. 72, p. 148-154. DOI : 10.1016/j.euromechsol.2018.04.016.

Meridian crack test strength of plasma-sprayed amorphous and nanocrystalline ceramic microparticles

V. Pejchal; M. Fornabaio; G. Zagar; G. Riesen; R. Martin et al. 

ACTA MATERIALIA. 2018. Vol. 145, p. 278-289. DOI : 10.1016/j.actamat.2017.12.031.

In-situ strength of individual silicon particles within an aluminium casting alloy

M. G. Mueller; G. Zagar; A. Mortensen 

Acta Materialia. 2018. Vol. 143, p. 67-76. DOI : 10.1016/j.actamat.2017.09.058.

Mechanical properties of MC multimetallic carbides in steel

L. Michelet / A. Mortensen (Dir.)  

Lausanne, EPFL, 2018. 

Stable room-temperature micron-scale crack growth in single-crystalline silicon

M. G. Mueller; G. Zagar; A. Mortensen 

Journal Of Materials Research. 2017. Vol. 32, num. 19, p. 3617-3626. DOI : 10.1557/jmr.2017.238.

The local strength of individual alumina particles

V. Pejchal; M. Fornabaio; G. Zagar; A. Mortensen 

Journal Of The Mechanics And Physics Of Solids. 2017. Vol. 109, p. 34-49. DOI : 10.1016/j.jmps.2017.08.005.

Probing the micromechanical strength of oxide ceramic composite reinforcements

V. Pejchal / A. Mortensen (Dir.)  

Lausanne, EPFL, 2017. 

Strength and fracture of silicon second-phase particles in aluminium casting alloys

M. G. Mueller / A. Mortensen (Dir.)  

Lausanne, EPFL, 2017. 

Microscopic strength of silicon particles in an aluminium–silicon alloy

M. Mueller; M. Fornabaio; G. Zagar; A. Mortensen 

Acta Materialia. 2016. Vol. 105, p. 165-175. DOI : 10.1016/j.actamat.2015.12.006.

Fracture toughness measurement in fused quartz using triangular chevron-notched micro-cantilevers

G. Zagar; V. Pejchal; M. G. Mueller; L. Michelet; A. Mortensen 

Scripta Materialia. 2016. Vol. 112, p. 132-135. DOI : 10.1016/j.scriptamat.2015.09.032.

The local strength of microscopic alumina reinforcements

G. Zagar; V. Pejchal; M. G. Mueller; A. Rossoll; M. Cantoni et al. 

Acta Materialia. 2015. Vol. 100, p. 215-223. DOI : 10.1016/j.actamat.2015.08.026.

On measuring fracture toughness under load control in the presence of slow crack growth

G. Zagar; A. Singh; V. Pejchal; M. G. Mueller; A. Mortensen 

Journal Of The European Ceramic Society. 2015. Vol. 35, num. 11, p. 3155-3166. DOI : 10.1016/j.jeurceramsoc.2015.04.004.

Fracture toughness testing of nanocrystalline alumina and fused quartz using chevron-notched microbeams

M. G. Mueller; V. Pejchal; G. Zagar; A. Singh; M. Cantoni et al. 

Acta Materialia. 2015. Vol. 86, p. 385-395. DOI : 10.1016/j.actamat.2014.12.016.