热处理对BT25Y合金电子束焊接组织和力学性能的影响

Effect of Two Typical Heat Treatments on Microstructure and Mechanical Property of Electron Beam Weldment of BT25Y

对BT25Y合金电子束焊接样品进行700℃/2 h AC的退火处理和940℃/2 h AC+600℃/8 h AC的固溶+时效处理工艺,研究2种热处理工艺对合金焊接区域的组织和力学性能影响。结果表明,无热处理情况下,焊缝溶合区主要由α′马氏体构成,焊缝区硬度和强度明显高于基体。700℃/2 h AC退火处理后,焊缝区的α′马氏体转变为细小弥散的α相,焊缝区的硬度和强度高于基体,室温拉伸断裂发生在基体,焊接样品具有较差的高温持久性能。940℃/2 h AC+600℃/8 h AC的固溶+时效处理,焊缝熔合区的α′马氏体转变为尺寸较大的片层α相,并且沿原始凝固β晶界存在尺寸较大的连续或断续棒状α析出带,该析出带使得焊接样品在室温拉伸时沿焊缝发生脆性沿晶断裂,该热处理后合金具有较好的高温持久性能。

The microstructures and mechanical properties of electron beam weldment BT25Y after 700 °C/2 h AC（AT） and 940 °C/2 h AC＋600 °C/8 h AC（SAT） were investigated. The results indicate that the fusion zone microstructure of non heat treatment（NHT） specimen is mainly composed of α′ martensite phase, which shows high microhardness and strength in comparison to base metal zone（BZ）. For the specimens after AT, the α′ martensite in FZ transforms to fine α phase which shows similar microhardness regular pattern in comparison to NHT specimen. The fracture appears in BZ because of lower hardness and strength of BZ in comparison to FZ. Under this condition the specimen shows bad high temperature endurance strength. For the specimens after SAT, the α′ martensite in FZ transforms to α phase with rather big size and there are continuous or interrupted big sized α precipitation bands along the original β grain boundaries. These precipitation bands in FZ lead to the brittle fracture of welded specimen. Under this condition the specimen shows better high temperature endurance strength.