论文部分内容阅读
在测定W-Mo高速钢和含Nb基体钢的疲劳裂纹扩展速率da/dN及门坎值△K_th的基础上,对裂纹扩展途径和断口形貌进行了SEM观察与分析。试验结果表明,在双对数坐标上,工模钢的da/dN-△K关系曲线明显分为三段,并各自遵循不同的扩展机制;低速区以沿晶开裂和不连续解理为主;中速区则遵循穿晶的“准解理+流变带开裂”机制;而高速区裂纹则以主裂纹前方的裂纹再生核方式向前延伸。da/dN-△K曲线的转折是相邻区域不同裂纹扩展机制相互竞争与转化的结果。
Based on the measurement of the fatigue crack growth rate da / dN and the threshold value △ K_th of W-Mo high-speed steel and Nb-containing steel, the crack propagation path and fracture morphology were observed and analyzed by SEM. The experimental results show that the da / dN- △ K relation curve of the tool steel is clearly divided into three sections in double logarithmic coordinates and each follows different expansion mechanisms; the low-speed section mainly consists of the crack along the crystal and the discontinuous cleavage While the middle-speed zone follows the mechanism of “quasi-cleavage + rheological zone cracking” of transgranular; however, the crack in the high-velocity zone extends forward in the way of the crack nucleation in front of the main crack. The transition of da / dN- △ K curve is the result of mutual competition and transformation between different crack propagation mechanisms in adjacent regions.