Phase transformation and microstructure evolution of pearlite heat-resistant steel during heating

Abstract

The phase transformation and microstructure evolution of pearlite heat-resistant steel during heating were observed with an ultra-high temperature confocal scanning laser microscope. The α-ferrite completely disappeared earlier than Fe3C during the formation of γ-austenite, which is inconsistent with the fact that the Fe3C should disappear completely earlier under equilibrium conditions. After the Fe3C + α→γ transformation, static recrystallisation of γ-austenite occurred, accompanied by the dissolution of cementite. During the γ→δ transformation, the δ-cell first precipitated at the triple point of the γ-austenite grain boundaries, and then the δ-cell platelet with one tip appeared in the γ-austenite grain. The law of δ/γ inter-phase boundaries was analysed based on inter-phase boundary types and element diffusion.

Microstructural Evolution and Mechanical Performance of Two Joints of Medium-Mn Stainless Steel with Low- and High-Alloyed Steels

“…Figure 14 d exhibits the chemical analysis of the precipitates (located at the grain boundaries) via the EDS; it confirms that they are Chromium carbides, as it mainly contains C, Cr, and Mn elements. It was reported that the precipitation of carbide particles on the grain boundaries has pinning effects on the grain growth [ 54 , 55 , 56 ]. Therefore, the precipitated carbides in the TZ work as obstacles for the movement of the grain boundaries, which hinders the coarsening of the grains size at the TZ and works as heterogeneous nucleation sites, which enhances the formation of fine equiaxed structures in the TZ; therefore, the size of the grains at the TZ was finer than the grains which exist at the FB and CGHAZ, which is similar to the results presented in the literature [ 52 , 57 , 58 ].…”