Orientation relationships of intragranular austenite in duplex stainless steel weld metals

Abstract

Formation and characteristics of fine intragranular austenite were studied for low energy input duplex stainless steel welds. Microstructures were largely ferritic with some allotriomorphic grain boundary austenite, Widmansta ¨tten type austenite, fine intragranular austenite and nitrides. Electron backscattered diffraction analysis revealed that grain boundary austenite had a random orientation relationship (OR) with one of the adjacent ferrite grains and was close to Kurdjumov-Sachs (KS) with the other, whereas Widmansta ¨tten austenite always showed an OR near KS. The finest intragranular austenite was mainly randomly oriented, whereas coarser austenite more often was close to KS. It is argued that the OR of intragranular austenite with the ferritic matrix is governed by a combination of composition, determining driving force for nucleation at temperature, cooling rate and the availability of nitrides acting as nucleation sites. A random OR is most likely for higher cooling rates and compositions promoting nucleation at lower temperatures.

Welding metallurgy of stainless steels during resistance spot welding Part I: fusion zone

“…[17][18][19][20] The cooling rate of RSW is significantly higher than that of the conventional arc welding processes. Gould et al 21 proposed a simple analytical model predicting cooling rates of resistance spot welds, as follows…”

Influence of resistance spot welding process parameters on dissimilar austenitic and duplex stainless steel welded joints

“…Also, the thickness of austenite layers was thin when compared to higher heat inputs and fails at 11,600 N. When the heat input is increasing further to 365.57 J, WA and increase of IGA was observed in the fusion zone. It may be the fact due to faster cooling rate 29 as shown in Figure 6 and fails at 12,100 N. Furthermore, the heat input was increased to the maximum level that is 820.03 J and observed that the thickness of austenite layer was increased with fine equiaxed grains and fails at 17,600 N. From the above discussion, the microstructure of weldments revealed that WMZ is dominated by increasing austenite layers with higher heat inputs. Also, for better clarification of this statement SEM (Scanning Electron Microscopy) test has been conducted at WMZ.…”

Microstructure and Impact Toughness of Local-Dry Keyhole Tungsten Inert Gas Welded Joints

“…Therefore, according to the calculated deviations from the exact K–S orientation, the phase boundaries of austenite and ferrite in DSS are divided into two types. Karlsson and Börjesson [17] revealed that the phase boundaries close to K–S orientation (within 6°) are special phase boundaries (SPB) and the phase boundaries with angles larger than 6° are random phase boundaries (RPB).…”