【摘要】 对DZ125定向凝固铸造镍基高温合金进行了应变比为-1.0的同相位三角波和同相位梯形波,550℃1000℃热/机械疲劳实验研究。实验结果表明:在相同应变幅下,同相位三角波载荷情况下的热/机械疲劳寿命比同相位梯形波载荷情况下的热/机械疲劳寿命长。研究了在两种载荷情况下材料的热/机械疲劳循环应力响应行为。试样断口的微观分析表明:在热/机械疲劳过程中,同时存在疲劳、蠕变和氧化损伤;在同相位三角波载荷下,穿晶+沿晶断裂为疲劳断裂的主要特征;在同相位梯形波载荷下,裂纹主要为沿晶萌生与扩展。这是导致在同相位梯形波载荷下疲劳寿命缩短的主要原因。更多还原

【Abstract】 The thermal-mechanical fatigue behavior of DS superalloy DZ125 was studied.A basic cycle has been used without hold time and with hold time at high temperature to simulate only the transient behavior of critical part of a blade. Both triangular and trapezoidal wave shape signals with in-phase cycle and at maximum and minimum temperature of 550℃and 1000℃ respectively.The ratio Rε of minimum to maximum strain is-1.0.At the same strain amplitude,it was found from test that the TMF life of in-phase cycle with triangular wave shape is longer than that of in-phase cycle with trapezoidal wave shape.Also the effect of hold time on cyclic stress response under conditions of triangular and trapezoidal wave shape was studied.The thermal-mechanical fatigue damage was discussed. The results show that fatigue,creep and oxidation damage always developed during TMF.Fracture is mainly intergranular and transgranular under conditions of triangular wave shape.The path of crack initiation and growth is transgranular under conditions of trapezoidal wave shape.更多还原