Precession Electron Diffraction Detection and Phase Mapping of Retained Austenite and Carbides in a Heat Treated Low Alloy Carbon Steel Using a JEOL ARM 200 TEM with an AppFive Topspin System for Synchronized Beam Scanning and Precession
Retained austenite in heat treated steels is usually measured using X-Ray diffraction, with protocols outlined in ASTM Standard E975 [1]. Retained austenite has been measured in high alloy steels with large grains of retained austenite using EBSD [2]. However, low alloy steels heat treated to reduce retained austenite may have small grains of retained austenite that cannot reliably be detected by EBSD [3] or X-Ray diffraction.
Characteristics of Retained Austenite in Quenched High C-High Cr Alloy Steels
In this paper, the morphologies of martensite and retained austenite for 1.5 mass%C-12 mass%Cr and 1 mass%C-8 mass%Cr steels were observed by means of optical microscopy, XRD, SEM/EBSD and TEM. The amount of retained austenites was quantitatively investigated and compared with XRD, EBSD and TEM observation methods. The retained austenites were distributed in the form of a block type and a film type in the martensite structures. For the 1.5 mass%C-12 mass%Cr steel, the amount of block type retained austenite and film type one are almost equal in three distinct regions of carbide; primary carbide, secondary carbide and without carbide. In the case of 1 mass%C-8 mass%Cr steel, as to film type retained austenite there are not so much differences among those regions. However, block type retained austenites are distributed with much amount, especially in the region around primary carbide. [doi:10.2320/matertrans.MRA2008161]
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.