Keywords: railway network, insulated rail joints, joint design, ball milling, yttria partially stabilised zirconia, microstructure.

The current study deals with an attempt to design and characterise a new generation of insulated rail joints constituted of two different parts. An insulated part will ensure the electrical insulation and a graded part will provide a progressive evolution of the mechanical properties between the insulated part and the rails, which enables a good compromise between the mechanical and the electrical properties. The graded steel based composite will be composed of several subparts made of metal matrix composite (MMC) reinforced by 3 molar percent of yttria partially stabilised zirconia (YSZ) particles and elaborated by powder metallurgy.

The current paper presents the first results concerned with the effect of the milling duration on the microstructure and the phase nature of Fe and 40 volume percent of YSZ powders. The predominant tetragonal zirconia phase stabilised by yttria and the monoclinic zirconia phase in a lower amount seems to be maintained stable up to 24 hours of milling but after 48 hours of milling, a new phase yttrium orthoferrite was formed, very like that resulting from the reaction between iron and yttrium oxide remaining in the initial YSZ powder. An increase of the milling duration also leads to a refinement and a homogenisation of the distribution of YSZ reinforcement in the Fe matrix. However the YSZ dispersion reached is not sufficient at a microscopic scale after 24 h of milling.

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