Abstract
The cracking initiation mechanism of high Cu-bearing nitrogen-alloyed austenitic stainless steel was systematically investigated by using a Gleeble-1500D simulator under different strains and deformation temperatures in the hot deformation process. The cracking initiation process and microstructure variations were characterized by optical microscopy (OM), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). In the deformation process, Cu-rich and Cr-rich phases were found around the microscopic crack at the strain of 0.5. Cu content was found to be higher at the grain boundary than inside the grain. The equilibrium phase diagram calculated by Thermo-calc shows that Cu precipitates out in the form of an elementary substance below 1022 °C, when the Cu mass fraction reaches 5%. Meanwhile, dislocation walls and twin crystals were observed by TEM. The results show that the synergistic effect of the secondary phases, such as M23C6 precipitated along the grain boundary and stress concentration, lead to crack generation, which is lower at high temperature and low temperature and is higher at 1100 °C and increase as the strain increases.
Highlights
IntroductionCu-bearing austenite stainless steels have been widely used in dentistry, orthopedics, and other medical applications due to their novel structural and strong antibacterial properties, which have been attributed to the Cu ions acting as the antibacterial agent [1,2]
In recent years, Cu-bearing austenite stainless steels have been widely used in dentistry, orthopedics, and other medical applications due to their novel structural and strong antibacterial properties, which have been attributed to the Cu ions acting as the antibacterial agent [1,2].enhancements in the high temperature strength of the steels can be achieved by the formation of tiny Cu-rich phase precipitates with nanometers sizes when an appropriate amount of Cu element is added in the steel [3]
Enhancements in the high temperature strength of the steels can be achieved by the formation of tiny Cu-rich phase precipitates with nanometers sizes when an appropriate amount of Cu element is added in the steel [3]
Summary
Cu-bearing austenite stainless steels have been widely used in dentistry, orthopedics, and other medical applications due to their novel structural and strong antibacterial properties, which have been attributed to the Cu ions acting as the antibacterial agent [1,2]. Yang et al [9] have revealed that the addition of Cu up to 3–4 wt.% is optimum because such addition leads to the appearance of Cu-rich phase precipitates with an ideal combination of size, number and spacing and accelerates the effect of Cu on the enhancement of the creep performance of steel. The excessive addition of copper to steels can have adverse effects on mechanical properties It can form low-temperature eutectic phases that preferentially segregate to the grain boundaries and embrittle the alloy [10,11]. Futamura et al [12] reported that the addition of up to 4 wt.% Cu to low carbon austenitic stainless leads to ain reduction ductility due to the segregation and precipitation of stainless steels leadssteels to a reduction ductility in due to the segregation and precipitation of Cu along the.
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