铍中Be2C及硅基夹杂对铍材伸长率的影响

铍材伸长率是目前限制铍材使用的关键因素.对高伸长率和低伸长率铍材的拉伸断口进行对比分析,发现在铍材的断裂源处往往含有非金属夹杂,夹杂造成的微裂纹是铍材解理断裂的裂纹核心.通常情况下,这些夹杂是以硅为基的杂质,一般不会造成铍材伸长率的明显降低.而当杂质中存在碳元素时,形成脆、硬稳定的Be2C,因Be2C难以变形,其断裂强度较铍材更低,因此在Be2C处容易位错集束而加重应力集中,并沿Be2C内部生成主裂纹,该主裂纹与原有的微裂纹合并后,裂纹长度加长,导致铍材解理速度加快,伸长率显著降低.

INFLUENCE OF Be2C AND Si BASE INCLUSIONS IN BERYLLIUM MATERIAL ON ITS ELONGATION

At the moment,employment of beryllium material is limited by its elongation.This paper makes a contrast study to the fracture surface of beryllium material with different elongation.It was acquired that crack source of beryllium material generally contains non-metallic inclusions,which caused micro cracks existing on its,then forming cleavage crack nucleating site of cleavage fracture later.Under normal conditions,these inclusions was Si base inclusion,which didn't caused beryllium material elongation remarkable dropped.But when C element was existence in inclusions,brittle and hard Be_2C was formed.Be_2C is stable and very difficult deformed,its ruptured strength is more lower than beryllium material matrix's,and it is likely to dislocation accumulation at the inclusion then stress concentration aggravated.Therefore Be_2C was preferentially separated and main crack was initiated in its internal.The main crack connected with former micro crack at crack source inclusions,crack length was increased,which induced beryllium material rapid cleavage,so the elongation was remarkable dropped.