EFFECTS OF ANTIBACTERIAL AGING TREATMENT ON MICROSTRUCTURE AND PROPERTIES OF COPPER-CONTAINING DUPLEX STAINLESS STEEL I. Microstructure and Evolution of Copper-Rich Phase

Nowadays, the events of bacterial infection are increasingly arising. It is urgent to develop new antibacterial material to fight against the bacteria having resistance to drug. Because the antibacterial stainless steels have both antibacterial property and other excellent combination ones, their development has been obtained rapidly. At present, the copper-containing antibacterial stainless steels are the research focus. It has been reached that the antibacterial effect of those materials is due to the copper-rich phases precipitated from the matrix by aging treatment. Most of studies were performed at single-phase stainless steels, but rarely at duplex stainless steels. It is necessary to study the precipitation process of copper-rich phases in duplex stainless steels for the development of antibacterial duplex stainless steels. In this work, the microstructure and precipitating evolution law of antibacterial duplex stainless steels. In this work, the microstructure and precipitating evolution law of copper-rich phases in the copper-containing duplex stainless steels during antibacterial aging treatment has been analyzed in detail by SEM, XRD and TEM. The results indicate that antibacterial copper-rich phases are precipitated from ferrite and alpha/gamma interfaces, no precipitation in austenite when the duplex stainless steels are aged at temperature ranging from 540 and 580 degrees C. The technique parameters of the aging treatment have important effect on the volume fraction and morphologies of precipitated phase. With aging time increasing, the precipitates coarsen, and their morphologies gradually change from spherical particle to rod-like or long-stripe-like grain. When the aging temperature is raised, precipitation speed of copper-rich phases accelerates and they make the change like before. At the same time; the copper-rich phases gradually turn from metastable state to steady epsilon-Cu phase with the composition close to pure copper, which has complicated multilayer structure with twisting layers. The Kurdjumov-Sachs orientation relationships between epsilon-Cu phases and the ferrite matrix followed: ((1) over bar1 (1) over bar)(epsilon-Cu)//((1) over bar(1) over bar0)(alpha-Fe); [011](epsilon-Cu)//[001](alpha-Fe), (11 (1) over bar)(epsilon-Cu)//((1) over bar2 (1) over bar)(alpha-Fe); [011](epsilon-Cu)//[012](alpha-Fe).