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Motivation, Objective 3/4 TRIP steels are adaptive materials. They are characterized by high fracture toughness and local hardening under high loads. 3/4 The local hardening effect is based on the formation of martensite disks and guarantees a high tensile strength. 3/4 Martensite takes a smaller volume than ferrite. Therefore the formatted martensite disks loosen partially from the ferrite matrix and generate acoustic emission events. 3/4 In standard TRIP steel most of the acoustic emission events arise directly at the yield point. After exceeding of the yield point the AE activity is very small. 3/4 However, an advantage of this steel consists in the fact that it is loadable locally far beyond yield point. In this region an AE monitoring is especially interesting. 3/4 Therefore one main purpose of the investigation was to search for material structures which effect an increasing of AE activity after the yield point. Horst Kühnicke, Ulf Waag Optimization of the AE behaviour of transformation induced plasticity (TRIP) steels Dresden DGZfP Proceedings BB 90-CD Poster 13 EWGAE 2004 Solution 3/4 Bringing in hard particles increases the AE activity after exceeding of the yield point. 3/4 Applicable hard particles are manganese sulfides (MnS), glasses and ceramics. 3/4 During the production process the steel undergoes a strong cold forming. In this process the hard particles must not be destroyed. 3/4 In order not to affect the material properties of TRIP steel negatively, a small number and a uniform distribution are necessary. That can be achieved best by a powder metallurgy manufacturing process. Horst Kühnicke, Ulf Waag Optimization of the AE behaviour of transformation induced plasticity (TRIP) steels Dresden DGZfP Proceedings BB 90-CD Poster 13 EWGAE 2004 The AE activity after exceeding of the yield point can be insignificantly increased by a changed thermal treatment of the steel. Bringing in MnS-particles leads to a significant increasing of the AE activity after exceeding of the yield point. Horst Kühnicke, Ulf Waag Optimization of the AE behaviour of transformation induced plasticity (TRIP) steels Dresden DGZfP Proceedings BB 90-CD Poster 13 EWGAE 2004 Raster-electronic images of individual MnS- inclusions before (above) and after (down) the load Microstructure of TRIP steel. The so- called martensite disks are black. Horst Kühnicke, Ulf Waag Optimization of the AE behaviour of transformation induced plasticity (TRIP) steels Dresden DGZfP Proceedings BB 90-CD Poster 13 EWGAE 2004 Data acquisition system AE.engine with DSP-Board 20 MHz sample rate Horst Kühnicke, Ulf Waag Optimization of the AE behaviour of transformation induced plasticity (TRIP) steels Dresden

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