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The microstructural changes in secondary carbides during spheroidized annealing (SA) and quenching and tempering (QT) processes in 60Cr16MoMA martensitic stainless steel has been comprehensively studied. Using scanning electron microscope, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, and transmission electron microscopy, a substantial dissolution of submicron-sized M23C6carbides after QT treatment was observed, leading to an increase in the mean carbides diameter. The highest solubility occurs at a 0.5 μm diameter, and carbide roundness improves during QT. Notably, the transformation of M7C3carbides into M23C6carbides was observed in QT samples through a multi-site in-situ nucleation mechanism. Additionally, it has been observed that Nb-rich MC carbides effectively restrict the growth of alloy carbides during heat treatment.

A promising process with the concept of ‘green, efficient and economic’ was carried out to produce a typical AISI D2 tool steel through curved continuous casting (C3). This study aims to demonstrate the segregation and eutectic carbides homogeneity in the C3 billets, which are the key points. The center porosity and center segregation are 2.0 and 1.0 respectively which are according to the standards GB/T 1979–2001 and YB/T 153–2015, and no shrinkage defects are found in the macrostructure. The segregation zones of C and Cr existed in the core and distributed dispersedly. Furthermore, the carbides showed three morphologies such as rod-like, coarse bulk-like and tortuous, where the rod-like carbides formed at the positions of edge to 3/4, the coarse bulk-like carbides emanated at 1/2 and core positions, and the tortuous carbides appeared somewhere in between. The morphologies of carbides are presumably caused by the inhomogeneous diffusion of C and Cr during the solidification. The maximum size of carbides increased and the area ratio of carbides decreased gradually at the positions of the edge to the core in the billets. The carbides evolved during high-temperature annealing, and it exhibited best dissolution which has less amount segregated at grain boundary with smaller size according to the results of experiments and theoretical calculation.

The thermal deformation behavior of Fe–32Mn–11Al-0.9C low density steel was investigated by Gleeble-3500 thermomechanical simulator through single pass compression test with deformation temperature of 900–1100 °C and strain rate of 0.01–1.0 s−1. The true stress vs.true strain curves and flow stress model under different deformation conditions were obtained. Dynamic recrystallization (DRX) behavior of δ-ferrite occurred before dynamic softening of austenite under specific deformation conditions which was studied by interrupted compression tests. The results suggest that the DRX behavior of δ-ferrite suppresses that of austenite and refines δ-ferrite grain. The DRX behavior of δ-ferrite becomes more obvious with increasing strain rate which is attributed to the increase in driving force, whereas it weakens with increasing deformation temperature owing to the advance of dynamic softening of austenite.