Fully pearlitic steel was wire-drawn up to a strain of 2.2. Torsion tests were performed using two types of specimens—one was an as-drawn specimen, and the other was aged at 423 K for 3.6 ks. A delamination crack propagated along the longitudinal direction of the wire in the aged specimen, whereas normal fracture was exhibited perpendicular to the longitudinal direction in the as-drawn specimen during torsion tests. Backscattered electron images indicated that the cementite lamellae beneath the delamination crack had vanished, whereas, in the as-drawn specimen, the cementite lamellae beneath the normal fracture surface had rotated until the fracture. Torsion tests with different strain rates indicated an inverse strain-rate dependence of the onset of the delamination, suggesting that the plastic deformability of ferrite and existence of the thermally activated process that controls the cementite dissolution indicate the onset of the delamination. In the present study, the effect of aging and deformability of ferrite on delamination is discussed, suggesting that the delamination crack propagates as a result of the local plastic instability on the scale of several microns.

将全珠光体钢拉丝至2.2的应变。使用两种类型的样品进行了扭力测试-一种是拉伸后的样品，另一种在423 K下老化3.6 ks。在老化的试样中，沿着金属丝的纵向方向会产生分层裂纹，而在扭转试验中，拉伸后的试样中会出现垂直于纵向方向的正常断裂。反向散射电子图像表明，分层裂纹下方的渗碳体薄片消失了，而在拉伸后的试样中，正常裂缝表面下方的渗碳体薄片一直旋转直到破裂。在不同应变速率下的扭转试验表明，分层的开始与应变速率成反比，这表明铁素体的塑性变形能力和控制渗碳体溶解的热活化过程的存在表明了层离的开始。在本研究中，讨论了铁素体的时效和可变形性对分层的影响，这表明分层裂纹是由于局部塑性不稳定性而在几微米尺度上传播的。