Papers by Author: Thorsten Manns

Abstract: The deformation behaviour of four super duplex stainless steels of the grade SAF 2507 (UNS S32750) were studied by X-ray diffraction experiment with in-situ uniaxial tensile load. The steels had different nitrogen contents, between 0.2 and 0.33%, and/or different volume fractions of the ferrite, between 37% and 49%, in balance with austenite. The development of phase-specific stresses under external loading up to over 10% tensile strain was followed. The X-ray diffraction measurements revealed that load partitioning between the phases changed with increasing applied load, as the ferrite and austenite exhibited different deformation hardening behaviours. At the onset of macroscopic yielding and low plastic strains, a load transfer from γ to α occurred due to higher yield strength and strain hardening rate of the ferrite but vice versa at larger plastic strains when the austenite hardened more rapidly than the ferrite. It was also concluded that both the yield and tensile strengthen of the steels increased with increasing nitrogen content due to increased strengthen of the austenite by additional solid solution hardening, whereas a higher volume fraction of austenite contributed to higher tensile strength.

Abstract: A Matlab based computer program was developed which gives the possibility to calculate the diffraction elastic constants (DEC) of macroscopically isotropic, single phase materials from their single crystal elastic constants. The proper function of the program was confirmed by means of results from literature. In almost all cases the results from the program DECcalc could reproduce the values and diagrams given in the appropriate publications. Discrepancies could always be assigned to the use of different single crystal coefficients.