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为了更好地了解体心立方(bcc)结构金属的循环变形机制,在恒总应变幅控制的条件下研究了含晶界孔洞粗晶工业纯铁的疲劳变形特征.结果表明,含晶界孔洞的粗晶工业纯铁在不同总应变幅“εt/2下均发生不同程度的循环硬化现象,无循环饱和阶段出现.疲劳寿命与塑性应变幅的关系基本符合Coffin-Manson法则.循环变形的表面变形特征与外加总应变幅具有一定的相关性:随着总应变幅的增加,滑移变形及其导致的挤出侵入现象更为严重,滑移开裂更趋显著;越来越多的原来位于晶界上的微观孔洞发生扭曲变形、聚合、长大而产生裂纹,甚至导致沿晶开裂.在相对较高的总应变幅下,在表面还观察到了滑移扭折现象以及沿晶裂纹扩展进入晶粒内部的现象.在低应变幅”εt/2=1.0×10-3下循环变形后发现了类驻留滑移带(PSB)楼梯位错结构,随着应变幅的增加,位错胞结构发展成为主要结构特征,其平均尺寸逐渐减小.
In order to better understand the cyclic deformation mechanism of bcc structural metal, the fatigue deformation characteristics of industrial pure iron with grain boundary cavity coarse grain were studied under the condition of constant total amplitude control. The results show that, Of the coarse-grained industrial pure iron in different degrees of total strain amplitude “εt / 2 under different degrees of cyclic hardening occurs, no cyclic saturation phase appears.The relationship between fatigue life and plastic strain amplitude basically consistent with Coffin-Manson law. With the increase of the total strain amplitude, the deformation of the surface and the extrusion intrusion caused by the deformation are more serious and the slip cracking is more significant. More and more original The microscopic holes located on the grain boundaries distort, polymerize, grow and produce cracks, and even cause the intergranular cracking. At relatively high total strain amplitude, the phenomenon of slipping kinks and the propagation of intergranular cracks And the dislocation structure like Stairway of Residing Slip Band (PSB) was found after cyclic deformation under the low strain amplitude of ”εt / 2 = 1.0 × 10-3. With the increase of strain amplitude, Skeletal structure development has become the major Fabric characteristics, an average size decreases.