服役经历对7N01铝合金断裂力学性能的影响

材料在服役过程中的可靠性和耐久性是结构安全评估的基础,针对某型高速列车上服役多年的7N01铝合金材料,进行实验室空气环境下断裂力学性能参数测试,并分析服役前后疲劳裂纹扩展行为差异.结果表明:服役经历促使材料的各项断裂力学性能退化,呈规律性下降趋势;服役材料稳态疲劳裂纹扩展阶段da/d N-ΔK关系曲线呈折线现象,分段拟合方法能够精确描述其疲劳裂纹扩展行为.微观形貌的结果显示:服役后7N01铝合金的疲劳裂纹早期扩展区、稳定扩展区和快速断裂区的断裂表面依次为脆性断裂特征、塑性疲劳条带和脆性疲劳条带混合模式及沿晶和穿晶的混合断裂形貌.

Effect of Service on Fracture Mechanical Properties of 7N01 Aluminum Alloy

The reliability and durability of materials in service are the assessment foundation of the structural safety. Aimed at the 7N01 aluminum alloy experienced a long term service in high speed trains， the fatigue mechanical properties were investigated in laboratorial atmosphere， and the fatigue cracks propagation (FCP) behaviors of materials with/without service were analyzed. The results showed that the experience of service deteriorates the mechanical properties， showing a regular decline trend. The da/dN-ΔK curve in the FCP zone after service showed a turning phenomenon， and a piecewise Paris’ curve fitting method was used to describe the FCP behavior. The results of the fracture surface morphologies showed that the are crack initiation zone， steady growth zone and rapid growth zone of 7N01 alloy after service corresponding to cleavage fracture mode， mixed plastic and cleavage fatigue striation， and mixed intergranular and transgranular fracture， respectively.