This paper deals with maraging steel, as a prospective material for the 3D printed lightened structural parts of transport means. Direct Metal Laser Sintering technology was tested for creation of a thin-wall structure with defined internal geometry. The referential samples prepared by the DMLS technology were examined under quasi-static and high strain rate loading using a servo-hydraulic testing machine at strain rates up to 1400 s-1. Microstructural analyses served for evaluation of structural homogeneity and metallurgy quality, including the influence of crystallization gradient. The stabile ductile fracture mode was proven by fractography analyses, even at a maximal strain rate. The post-impact tests were conducted to evaluate the local residual plasticity by indentation tests.
The usability of the magnetic Barkhausen noise (MBN) technique for monitoring the critical state of plastic straining in the case of interstitial free (IF) steel is demonstrated. IF steels are frequently employed in the automotive industry (e.g., automotive body parts—doors, trunks, wheel arches, etc.), and rupture of components made of these steels occurs during cold forming. Alteration of microstructure expressed in many terms and the corresponding MBN features after the variable degree of plastic strains developed by the uniaxial tensile loading are investigated. It is reported that the effective value of MBN, as well as the shift of MBN envelopes toward higher magnetic fields, can be proposed as the suitable MBN features alerting the incoming matrix breakage. Moreover, the higher MBN in the direction of exerted load at the expense of the perpendicular direction can be found as a result of domain walls realignment.
This paper deals with the problematics of tensile testing of maraging steel lightweight cylindrical samples with internal structures, intended for automotive application. The samples were made with DMLS technology and tensile tested under the static strain rate of 0.002 s-1. During the loading, uneven deformations and multiple necking occurred on the samples. The mentioned effect significantly affects the state of stress and deformation at the final fracture zone, as well as the total deformation into the fracture, which means that it actually distorts the standard tensile test record. Therefore, a methodology for capturing the deformation response using the ARAMIS optical system was proposed. The methodology is presented and verified by a set of experiments for BCC internal structure.
Interstitial Free (IF) steels are nowadays commonly used for stamping complex parts of outer automotive bodies. Current requirements for fast production lead to the need of monitoring the real state of the material after stamping based on its real material conditions. It is desirable to describe and quantify the evolution of microstructure deformation and plastic conditions before and after the stamping process. This paper presents Electron Backscatter Diffraction analyses of deformed and non-deformed IF steel, including the quantitative measurement of the localized plastic response of the real stamped part, using an unconventional indentation method. The effect of strain rate was evaluated using the highspeed tensile tests. The increased ratio of the Low Angle Grain Boundaries was found as a good parameter to quantify the depletion of plasticity.
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