通过拉伸试验及平面应变断裂韧性测试,研究不同时效制度对2A97合金强韧性的影响,并利用透射电镜和扫描电镜对合金的微观组织及断口形貌进行观察.结果表明:2A97合金在135℃单级时效时断裂韧性较好,但强度偏低;双级时效可促进强度的提高,但第二级时效温度过高时(175℃),断裂韧性迅速下降,经过(135℃,36h)+(150℃,18 h)时效,可得到较好的强韧性匹配,其σb、σ0.2和KIC分别为547 MPa、489 MPa和28.9 MPa.m1/2.2A97合金中的主要强化相为δ'相和T1相.δ'相易共面滑移而引起应力集中,对合金韧性不利;T1相能有效地阻止位错滑移,对合金强度有显著提高.2A97合金在时效初期以穿晶和沿晶混合型断裂为主,断口表现出明显的分层特征,具有较好的韧性;随时效时间的延长,析出相的体积分数、尺寸以及临界分切应力增大,所造成的应力集中更明显,同时晶界平衡相增多,晶界无沉淀带加宽,沿晶断裂比例增多,合金韧性急剧下降.
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