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利用扫描电镜(SEM)、透射电镜(TEM)和电子探针(EPMA)对比分析综合机械性能良好和零延伸率的金属铍材室温拉伸断口形貌和微观组织,研究金属铍室温断裂行为,并着重分析微观组织缺陷对金属铍室温断裂行为的影响规律。结果表明:金属铍室温拉伸断口形貌表现为准解理的断裂特征。解理裂纹形核后,裂纹扩展不受阻挡,表现为完全的脆性,因此铍材有限的延伸率主要来自于微裂纹形核阶段。铍材内部存在的杂质相汇聚区、片状晶体疏松和孔洞等组织缺陷,相当于在铍材内部预制一定尺寸的微裂纹,一旦微裂纹尖端形成,这类缺陷就会成为解理裂纹晶核,使铍本身的屈服过程不能发生,是降低铍材延伸率的主要原因;致密的大颗粒杂质相与基体失配、或在局部区域出现的粗晶粒与周围细晶粒不匹配,均易在铍材内部造成应力集中,也是降低铍材延伸率的原因。另外,当杂质相在晶界形成连续薄膜状晶界组织,导致铍材晶界结合强度降低,引起晶界断裂,造成铍材延伸率降低。
The tensile fracture morphology and microstructure of beryllium metal with good mechanical properties and zero elongation at room temperature were analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM) and electron probe (EPMA). The fracture behavior of beryllium at room temperature was studied. The influence of microstructure defects on the rupture behavior of beryllium at room temperature was analyzed emphatically. The results show that the tensile fracture morphology of Beryllium beryllium is characterized by quasi-cleavage at room temperature. Cleavage crack nucleation, the crack growth is unobstructed, showing complete brittleness, so the limited elongation of beryllium mainly from the micro-crack nucleation stage. Beryllium material exists within the impurity phase aggregation zone, flaky crystals and holes and other organizational defects, which is equivalent to the beryllium prefabricated within a certain size of micro-cracks, once the tip of the micro-crack formation, such defects will become cleave crack nuclei , So the yield process of beryllium itself can not occur, is to reduce the main reason for the elongation of beryllium; dense bulk impurity phase and the matrix mismatch, or in the local area of coarse grains and peripheral fine grains do not match, are easy The stress concentration inside the beryllium material also reduces the elongation of the beryllium material. In addition, when the impurity phase forms a continuous thin film grain boundary structure at the grain boundary, the bond strength at the grain boundary of the beryllium material decreases, causing the grain boundary to break, resulting in the decrease of the beryllium material elongation.