MS39-P05 Use of X – ray diffraction  method for  residual stresses measurements in lean duplex stainless steel welds. Naima Ouali (Metallurgy and mechanical departement, Algiers, Algeria) Brahim Belkessa (CRTI, Algiers, Algeria) Billel Cheniti (CRTI, Algiers, Algeria) Walid Bedjaoui (CRTI, Algiers, Algeria)email: oualinaima@yahoo.frIn welding processes, the used of adequate energy is very important, it should be sufficient to prevent sticking but not too large to prevent grain growth, resulting in intense residual stresses and a decrease in mechanical properties of materials [1]. This research investigated effects of weld heat input and thus the cooling rate on mechanical properties in particularly residual stresses evolution.
The studied material  was received in the form of 6mm lean duplex stainless steel rolled sheet, LDX 2101(EN 1.4162, UNS S32101). The plates with single-V groove were joined using a TIG process for three different heat inputs.
Microstructures of different zones were observed and captured using optical microscope and scanning electron microscope (SEM) with an EDS analyzer. The ferrite content was assessed in light optical microscope using image analysis software. The X-ray diffraction method which employs Bragg’s theory was used to evaluate the residual strains then the residual stresses present within the weld. The extents of longitudinal and transverse residual stresses were carried out on the basis of the sin2ψ method, which is very employed for polycrystalline materials [2].
 
The microstructural analysis revealed different regions with a fusion zone which contains more austenite than the heat affected zone HAZ and parent material [3]. It is observed an increase in amount of austenite in weld metal within heat input increases, this low ferrite content in the weld can be attributed to high Ni content in the filler metal (7.5–9.5 % Ni) and the presence of austenite stabilizer N2 in shielding gas.
 
The measurements of RS were made on the {211} atomic plane of the studied material at 2θ= 156.105°, presented compressive stresses in longitudinal and transverse directions reaching a maximum stresses in the weld area. These residual stresses are due to high plastic deformation and temperature gradient involved in weld metal.
 
 
References:

[1] Gunn. R. N. 2003. Duplex stainless steels-Microstructure, properties, and applications.

[2] Syahida. N, Nasir. M, Khairul. M, Abdul. A, Mamat. S, & Iqbal. M, 2016. Review on Welding Residual Stress, ARPN J. Eng. Appl. Sci. 11(9), p 6166–6175.

[3] Kumar. S & Shahi. A. S, 2011. Effect of Heat Input on the Microstructure and Mechanical

Properties of Gas Tungsten Arc Welded AISI 304 Stainless Steel Joints, Mater. Des., Elsevier

Ltd, 32(6), p 3617–3623.



Keywords: Lean duplex stainless steel, XRD method, residual stresses