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体心立方金属循环变形的位错组态研究工作目前开展得还不多,Mughrabi等用透射电镜观察了α—Fe循环变形过程中的位错组态;Mori等人研究了Fe—Si单晶循环周次和位错结构之间的关系。我们观察了不同循环周次下铌单晶的位错组态,也就是塑性应变幅恒定时循环硬化曲线上各部分的位错组态。选用轴向为[321]方向的铌单晶(单滑移系)。其循环硬化曲线见图1(塑性应变幅e_P=4.5×10~3)。曲线明显地分成三个阶段:Ⅰ.小应变阶段(曲线缓慢上升);Ⅱ.快速硬化阶段(曲线急速上升);Ⅲ.饱和阶段(曲线趋向水平)。在曲线中选择A、B、C、D四点观察其位错组态,电镜观察选用(101)面(滑移面)和(111)面(垂直于滑移方向的平面)。滑移面(101)面上布氏矢量b_P的方向为[111]。 A点(e_(cum)=0.09)处于循环硬化曲线的第Ⅰ阶段。(101)面上位错组态为许多较密集的位错网络和碎块状的位错圈,位错网络中刃型位错占相当一部分的比例,虽然位错还没有形成条带,但已看出局部地区位错开始缠结。
Muchrabi et al. Observed the dislocation configuration during the cyclic deformation of α-Fe by transmission electron microscopy. Mori et al. Studied the effect of dislocation configuration of Fe-Si single crystal Relationship between cycles and dislocation structures. We observe the dislocation configuration of niobium single crystals under different cycles, that is, the dislocation configuration of each part of the cycle hardening curve when the plastic strain amplitude is constant. The use of axial direction [321] direction of niobium single crystal (single slip system). The cycle hardening curve shown in Figure 1 (plastic strain amplitude e_P = 4.5 × 10 ~ 3). The curve is clearly divided into three phases: I. small strain phase (slow rise of curve); II. Fast hardening phase (sharp rise of curve); 3. saturation phase (trend of curve). Select the four points A, B, C and D in the curve to observe the dislocation configuration. The (101) plane (slip plane) and (111) plane (the plane perpendicular to the slipping direction) are selected by electron microscopy. The direction of the Brinell vector b_P on the slip plane (101) is [111]. Point A (e_ (cum) = 0.09) is in stage I of the cycle hardening curve. The dislocations on the (101) plane are configured as many dense dislocation networks and dislocations, and the dislocations in the dislocation network account for a significant proportion of the dislocations. Although no dislocations have been formed yet, Seen in the local dislocation began to tangle.