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TRR188_B03­-Damage initiation of DP800 at the micro scale

The TRR 188 aims for a thorough understanding and quantitative control of damage in advanced materials. As a subpart of TRR188, this project aims at microscopically studying the initiation of damage on dual phase steel DP800.

DP800 consists typically of ferrite as the matrix and dispersed martensite islands. This material exhibits not only excellent mechanical properties like high strength and high strains to failure, but also is economically superior due to few required alloying elements.

Fig. 1:(a) Engineering stress versus strain curves for three representative pillars, labeled with the determined activated slip plane. (b) The cumulative probability function (CPF) of the CRSS for the three slip plane families [1].

 

The size dependent Critical Resolved Shear Stress (CRSS) and corresponding active slip systems of ferrite is investigated by pillar compression [1] while the fracture initiation toughness of damage sensitive sites, i.e. martensite islands, is measured by microcantilever bending tests [2].

Fig. 2: (a) Representative force-displacement curve of a tested sample exhibiting crack growth. (b) Corresponding as milled micro cantilever [2].

The project thereby is not only closely linked to the method development in the micromechanics group, but also has numerous partners for synthesis, characterisation and modelling within the TRR 188.

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