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本文探讨硅钢在挛晶机制下解理断裂微观模型。为此,进行光滑拉伸试验,切口试样四点弯曲试验,测定了不同晶粒度的Fe、1.5Si-Fe、3Si-Fe、4Si-Fe钢的屈服强度和解理断裂强度。本文阐述了硅钢的屈服强度和解理断裂强度在孪晶机制下的特点。在低温时,屈服强度有一段不随温度变化;解理断裂强度随温度下降而减小。本文提出硅钢孪晶引发的解理断裂的微观机制是:在高应力控制下“交叉孪晶成核—扩展控制”的模型,其解理核大小等于孪晶相交宽度。还提出在高应变下,由于挛晶的通道断裂,存在“交叉孪晶成核—微裂纹—扩展”模型。利用Griffith公式计算了一对交叉孪晶成核后扩展的有效表面能为4～12焦耳/米~2。
This article discusses the microscopic model of cleavage fracture of silicon steel under the twinning mechanism. For this purpose, the four-point bending test of smooth tensile test and incision test was carried out to measure the yield strength and cleavage fracture strength of Fe, 1.5Si-Fe, 3Si-Fe and 4Si-Fe steels with different grain sizes. This paper describes the yield strength and cleavage fracture strength of silicon steel under the twinning mechanism. At low temperatures, the yield strength does not vary with temperature for some time; the cleavage fracture strength decreases with decreasing temperature. In this paper, the micromechanism of cleavage and fracture caused by twinning of silicon steel is proposed. The model of “twinning nucleation and extension control” under high stress control has a cleaved nucleus size equal to the width of twin intersections. It is also proposed that at high strains, there is a “twinned twin nucleation-microcrack-expansion” model due to the rupture of the channel of twinning. Using Griffith formula, the effective surface energy of a pair of crossed twins after nucleation is calculated to be 4 ~ 12 J / m ~ 2.