Ta/Ta_(0.5)Hf_(0.5)C层状复合材料的抗等离子火焰冲击行为及机制

Thermal Shock Behavior and Mechanism of Ta/Ta_(0.5)Hf_(0.5)C Laminated Composite Under Plasma Flame

Ta/Ta_(0.5)Hf_(0.5)C层状复合材料是一种极具潜力的耐超高温结构材料,但抗热冲击性能鲜有报道。设计以超高温等离子火焰对复合材料进行脉冲考核,测试了材料考核过程中的温升数据及考核前后的微观组织和宏观形貌变化。在此基础上,利用有限元软件模拟了材料考核过程中的热应力分布,并指导开展了应力循环加载试验,分析了材料的抗热冲击机制。结果表明,复合材料经等离子火焰脉冲考核120次无裂纹生成。考核过程中,复合材料内部最大热应力数值约为207MPa。复合材料自身的高强度和优异的抵御裂纹扩展能力是其优异抗热冲击性能的主要原因,其经210MPa应力循环加载120次后,强度和韧性保留率分别高达70.1%和73.9%。

Ta/Ta_(0.5)Hf_(0.5)C laminated composite shows great potential to be used as wing leading edges and nose caps due to its good mechanical properties and ablation resistance.However,the thermal shock behavior of the composite is rarely reported,as such,it is hard to evaluate whether the composite can serve as a structural material stably.The plasma flame and finite element method(FEM)were employed to investigate the thermal shock behavior of Ta/Ta_(0.5)Hf_(0.5)C laminated composite.By analyzing the morphologies and microstructure of the tested sample,it is found that Ta/Ta_(0.5)Hf_(0.5)C laminated composite possesses great thermal shock resistance since no cracks are observed on the internal and external surfaces of the composites after 120 cycles of plasma flame pulse assessment.Based on the measured temperature during thermal shock testing,the thermal stress distribution field inside the testing sample was built successfully.Result reveals that the maximum thermal stress(207 MPa)caused by plasma flame occurs at the moment of cooling.After 120 cycles of stress cycling,the retention rates of strength and toughness of the composites are 70.1%and 73.9%,respectively.High strength and excellent crack propagation resistance are the main reasons for the excellent thermal shock resistance of Ta/Ta_(0.5)Hf_(0.5)C laminated composite.