Aged Duplex Research Articles

Influence of defect shape on damage evolution and fracture behavior of ductile materials

A generalized standard material model is developed for ductile materials containing aligned defects with arbitrary shape under self-similar expansion based on the work of Nguyen and Bui [Sur les materiaux elastoplastiques a ecrouissage positif et negatif. J. Mecanique 13, 321 (1974)] and Rousselier [Finite deformation constitutive relations including ductile fracture damage, in Three-dimensional Constitutive Equations and Ductile Fracture (Edited by S. Nemat-Nasser), pp. 331–355, North-Holland (1981)]. The influence of defect shape on damage evolution and instability of the material is investigated. The finite element calculation is made for notched and cracked specimens, with microvoid and microcrack damage. The result shows that the defect shape has significant influence on the fracture initiation and crack growth behavior. The present model is also applied to predict the J-resistance curve of a CT specimen for an aged duplex stainless steel, and the results are in good agreement with the experiment.

Fatigue crack propagation mechanisms in a thermally aged duplex stainless steel

Zeron 100 duplex stainless steel is susceptible to embrittlement following ageing at temperatures between 350 °C and 450 °C. The embrittlement is associated with cleavage of the age-hardened ferrite phase, initiated by deformation twinning. This can result in order of magnitude increases in the fatigue crack propagation rate. The effects of ageing on the mechanisms of fatigue crack propagation in Zero 100 are investigated, and a quantitative model is developed, accounting for the effects of hardness, temperature, stress level and microstructure on the fatigue crack growth rate.

Some new aspects on microstructural and morphological evolution of thermally aged duplex stainless steels

Improvements in the experimental procedure and refinements in the statistical analysis of atom-probe data allow a more accurate description of the kinetics of spinodal decomposition in duplex stainless steels aged between 300 and 400°C. The territe decomposition process at these temperatures appears to be more complex than previously considered. Whereas the initial stages follow what is expected for a spinodal decomposition, the α-α′ bimodal Cr-concentration frequency distribution tends towards a multimodal one as aging proceeds and temperature increases. On the Cr-rich α′ side of the histogram a Cr-60% peak develops, while the predominant Cr 40% peak seems to be quasi-metastable. Moreover, concentration profiles exhibit several wavelength families. The first wavelengths which appear are on the order of a few nanometers. Upon prolonged aging, larger correlation distances, one order or two orders of magnitude larger, emerge, leading to a structure with internal similarities.

HREM study on α′ and γ2 precipitation in an aged wrought duplex stainless steel at 500°C

HREM study on α′ and γ2 precipitation in an aged wrought duplex stainless steel at 500°C

Effect of crystallographic orientation of austenite on the formation of cleavage cracks in ferrite in an aged duplex stainless steel

Effect of crystallographic orientation of austenite on the formation of cleavage cracks in ferrite in an aged duplex stainless steel

HREM study on precipitated phases in the ferrite of aged wrought c-type duplex stainless steel

HREM study on precipitated phases in the ferrite of aged wrought c-type duplex stainless steel

Polarization Behavior of Austenitic and Duplex Stainless Steels in the Double Loop Reactivation Test

Abstract The corrosion behavior of AISI 304L and 308L stainless steels (SSs) in electro-potentiostatic reactivation (EPR) tests has been investigated using the double loop technique. The AISI 304L SS was tested in the fully austenitic and in the duplex (γ + δ) condition; the AISI 308L SS was in the form of a submerged arc weld metal having a duplex microstructure. The materials were aged at 700 C to induce phase transformation and sensitization and EPR tests were conducted both before and after the aging treatments. In tests on unaged material, single peaks in the corrosion current were detected in both the activation and reactivation potential scans (Ia and Ir respectively), and in the aged austenitic AISI 304L SS, the effects of sensitization were manifested, as expected, by an increase in both Ir and the ratio Ir to Ia. In tests on aged duplex materials, the increase in the height of the previously identified reactivation peak was accompanied by the appearance of a second reactivation peak, which coinc...