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不同的热加工工艺导致双相不锈钢2205(50/50铁素体/奥氏体)产生了不同的断裂韧性,尤其是断裂韧性降至不可接受的低值。本文通过分析透射电子显微镜研究其显微结构,对这种现象提供了解释。尤其是对断裂韧性的急剧变化提出了试验上的观察与分析,获得正确且有效的解决此类问题的方法。β-Cr2N相沿{110}α原子平面析出是导致断裂韧性降低,特别是在低温下的断裂韧性大幅降低的根本原因。因为在韧性至脆性转变温度时形变的机制为位错的移动性,而沿{110}α原子平面析出的β-Cr2N相阻碍了位错的运动,导致α铁素体的脆性,从而使材料整体脆化。材料经1200℃退火随即空气冷却到室温之后,断裂韧性恢复到正常值,是由β-Cr2N相的溶解所致。α-Fe(Cr)→α-Fe+α′-Cr相变(又常称为在475℃失稳分解)导致断裂韧性在低温与室温下都急剧下降是由富铬的铁素体α′-Cr固有的脆性所引起。将材料加热致800℃后随即急冷至室温后,断裂韧性恢复到正常值。这是由于材料经加热将α-Fe+α′-Cr相溶解并经急冷而避免了α-Fe(Cr)→α-Fe+α′-Cr相变的再发生。本研究中观察到的析出相的尺寸均为纳米量级,只有应用分析透射电子显微镜后才可得以同时获得其形态、化学成分以及晶体学的结果,从而解释断裂韧性变化的根本的原因,并找出解决问题的办法。
Different thermal processing techniques result in different fracture toughness for duplex stainless steel 2205 (50/50 ferrite / austenite), especially the fracture toughness drops to unacceptably low values. This article analyzes the microstructure of transmission electron microscopy, providing an explanation for this phenomenon. Especially for the rapid change of fracture toughness, we put forward the experimental observation and analysis to get the correct and effective method to solve such problems. The precipitation of the β-Cr2N phase along the {110} α atomic plane is the root cause of a decrease in fracture toughness, especially at low temperatures. Because the mechanism of deformation at ductile to brittle transition temperature is the dislocation mobility, the β-Cr2N phase precipitated along the {110} α atomic plane impedes the movement of dislocations, resulting in the brittleness of α-ferrite so that the material Overall embrittlement. The material was annealed at 1200 ° C and then air cooled to room temperature, the fracture toughness returned to normal, due to the dissolution of the β-Cr2N phase. α-Fe (Cr) → α-Fe + α’-Cr phase transformation (often referred to as instability decomposition at 475 ° C) results in a sharp decrease in fracture toughness both at low temperatures and at room temperature, -Cr inherent brittle caused. The material is heated to 800 ℃ immediately after quenching to room temperature, the fracture toughness returned to normal. This is due to the fact that the material is heated to dissolve α-Fe + α’-Cr phase and quenched to avoid the recurrence of α-Fe (Cr) → α-Fe + α’-Cr transformation. The sizes of the precipitates observed in this study are all on the order of nanometers and the fundamental reason for the change in fracture toughness can be explained by the simultaneous analysis of morphology, chemical composition and crystallographic results using transmission electron microscopy Find a solution to the problem.