关键词: 奥氏体不锈钢, 晶粒尺寸, 均匀性, 塑性, 裂纹

Abstract: Specimens taking from the center and 1/4 thickness positions along the thickness direction of 316H austenitic stainless steel hot-rolled plates were solution treated, and their microstructures with different grain sizes and distributions were obtained in order to investigate the effect of grain distribution characteristics on the mechanical properties of the austenitic stainless steel during service. The effect mechanism of grain size and uniformity on strength and plasticity was analyzed using high-temperature tensile testing and in-situ microstructure observation. The results show that as the average grain size increases, the strength of the 316H steel decreases and the total elongation increases, while as the grain distribution non-uniformity increases, the plasticity significantly decreases. During stretching process, grain boundaries deforms first and gradually initiates cracks, while plastic deformation mainly occurs inside the grains. As the loading force increases, cracks gradually propagate along the grain boundaries, causing the entire grains to separate. The difference in grain size in the microstructure preferentially leads to the initiation and propagation of cracks at the boundaries of large/small grains, forming obvious source of cracks. This heterogeneous distribution of grains significantly deteriorates the plasticity of the steel and should be avoided as much as possible.

Key words: austenitic stainless steel, grain size, uniformity, plasticity, crack