一种镍基高温合金PLC效应的温度依赖性研究

INVESTIGATION OF TEMPERATURE DEPENDENCE OF PLC EFFECT IN A NICKEL BASE SUPERALLOY

研究了温度对一种镍基高温合金Portevin-Le Chatelier(PLC)效应的影响.在恒定的拉伸速率5×10^(-4)s^(-1)下,从室温到900℃温度范围内进行拉伸实验,分析PLC效应发生的临界应变、应力跌幅、等待时间和飞行时间随温度的变化规律,揭示PLC效应的温度依赖性,探讨不同温度范围内PLC效应产生的微观机理.结果表明:从室温到450℃,随着温度升高PLC效应发生的临界应变减小,应力跌幅增大,表现为正常PLC效应,该过程为溶质原子气团向可动位错扩散并对其形成有效钉扎控制;而从450℃到600℃,随温度的升高临界应变增加,表现为反常PLC效应,该过程为位错第一次摆脱溶质原子气团的钉扎而脱钉自由飞行的过程控制.当超过一定温度后,由于不能形成有效的溶质原子气团对位错进行钉扎,因此不会发生PLC效应.

The temperature dependence of Portevin Le Chatelier （PLC） effect in a nickel base superalloy was investigated. A series of tensile tests were conducted ranging from room temperature to 900 ℃ at a constant rate 5×10-4 s-1. The critical strain, amplitude of stress drop, waiting time and flying time of serrated flow were analyzed in order to reveal the temperature dependence of PLC effect and its related micro mechanism. The results showed that the normal behavior occurs as temperature changes from room temperature to 450 ℃, in which the critical strain of serrated flow decreases with increasing temperature while magnitude of the stress drop increases. The normal PLC effect is mainly controlled by pinning effect of solute atoms and its diffusion process. When temperature increases from 450 ℃ to 600 12, the critical strain of PLC effect increases and the inverse PLC effect appears. Since some dislocations are pinned by solute atoms prior to breakaway, the dominant factor of inverse PLC effect is that pinned dislocations get rid of solute above 600 ℃, PLC effects disappear because it is to lock mobile dislocations. atoms and move freely. With temperature increasing difficult to form effective solute atmosphere necessary