Microstructure evolution in warm forged sintered ultrahigh carbon steel

Accelerated Spheroidization of Cementite in Sintered Ultrahigh Carbon Steel by Warm Deformation

“…Relations of strain rate to peak and critical strains are shown in Figure 3b. The critical strain during deformation of UHCS with high density of dislocations accumulated inside the martensite was significantly smaller than for the as-sintered state [23].…”

“…Superplasticity is generally first found in tensile tests, which were not carried out on our material due to the shape and size of the sintered specimens. Only compression and warm forging [22,24] tests were conducted, and it is quite possible that tensile superplasticity existed. For engineering applications, warm working such as forging is more relevant, and superplastic deformation did not occur in our spheroidized material [22,24], though it cannot be excluded in similar processing conditions.…”

“…In one, the rings were forged on a screw press between flat plates at 700-750 °C. In the second set of experiments, carried out on a Gleeble HDV-40 machine at Technische Universität Bergakademie Freiberg, discs were compressed at strain rates of 10 −3 , 10 −2 , 10 −1 , and 1 s −1 to ~1.15 natural strain [22][23][24]. Superplastic behavior was not observed.…”

“…An alternative way of warm working the steel is in a quenched state. The critical strain needed for transformation of microstructure via dynamic recrystallization is smaller for the initial martensite microstructure than for initial pearlite microstructure, which is associated with a high density of dislocations after quenching [8,21,23]. Investigation of warm deformation of quenched Fe-0.85Mo-0.65Si-1.4C, including the search for superplastic behavior, is the subject of this communication.…”