双相不锈钢多层多道焊接接头微观组织表征

采用钨极氩弧焊制备了双相钢焊接接头，基于热力学方法计算了母材和焊缝的平衡相变过程，采用OM，SEM，EDS，TEM等方法表征了接头不同区域的微观组织.结果表明，焊缝中添加镍显著促进γ形成并抑制Cr₂N析出.焊缝和热影响区γ₁主要包含晶粒边界奥氏体、魏氏奥氏体和晶粒内奥氏体，不同类型的奥氏体呈现显著的成分差异.焊缝和热影响区析出两种类型的γ₂:晶粒内γ₂和晶粒间γ₂.γ₂易于在δ内和δ/γ₁边界处富Ni和N元素而贫Cr和Mo元素的区域析出.Cr₂N主要分布于热影响区的δ内、δ/γ₂边界以及δ/δ边界处.

Microstructure characterization of duplex stainless steel multi-pass welded joint

Duplex stainless steel (DSS) welded joint was fabricated by tungsten argon arc welding method. Equilibrium phase transformation processes of base material and weld were calculated by thermodynamic method. Microstructures in different zones of DSS welded joint were characterized by optical microscope, scanning electron microscope, energy dispersive spectroscopy, and transmission electron microscopy. The results showed that the Ni addition in the weld significantly promoted austenite (γ) formation and prevented Cr₂N precipitation. The primary austenite (γ₁) in the weld and the heat affected zone (HAZ) mainly consisted of grain boundary austenite, Widmanstatten austenite, and intragranular austenite. There were obvious composition differences in the different types of austenite. Furthermore, there were two types of secondary austenite (γ₂) in both the weld and the HAZ: intragranular and intergranular γ₂. The γ₂ were easy to precipitate within the ferrite (δ) and in the/γ₁ interface where enriched in Ni and N element while depleted in Cr and Mo element. In the HAZ, the Cr₂N were mainly precipitated within the grain, in the/γ₂ interface, and in the/boundary.