Al-4%Ag合金中Ag原子偏析的低温正电子湮没参数研究

Study on Positron Annihilation Parameters of Low Temperature Segregation of Ag Atoms in Al-4%Ag Alloy

分别研究了823 K淬火处理和20%形变量的Al-4%Ag低温下Ag析出物对正电子的捕获行为的变化。采用正电子湮没寿命谱(PALS)技术和符合多普勒展宽能谱(CDBS)在温度范围10~293 K内对其进行表征。多普勒展宽能谱结果表明2种样品中均存在Ag析出物。正电子寿命谱的解谱结果中的各组分给出了Ag析出物随测量温度的变化规律。在170~273 K之间,正电子湮没行为具有较强的温度依赖性。但对于两个具有不同类型缺陷的样品,在低于170 K时观察到样品中Ag析出物捕获正电子能力出现了差异。随着测量温度的降低,淬火样品中的Ag析出物的正电子寿命和强度基本不变。在低于170 K的测量中,形变样品中的Ag析出物对正电子的捕获能力仍旧存在着较强的温度依赖性,但是变化幅度在逐渐减弱。当测量温度提升到室温(273~293 K),越来越多的正电子从Ag析出物中逃逸,逐渐回到自由状态或被其他深陷阱所捕获,失去了对温度的依赖性。

The positron trapping behavior of Ag precipitates at 823 K quenched and 20%deformation Al-4%Ag alloy at low temperature was studied respectively.It was characterized by positron annihilation lifetime spectroscopy(PALS)technology and coincident Doppler broadening spectroscopy(CDBS)in the temperature range of10~293 K.The positions of the Ag precipitate peak in the Doppler broadening spectrum shows that there are Ag precipitates in both samples.The components of the lifetime spectrum analysis results show that the change of Ag precipitates with the measurement temperature has a strong temperature dependence at the range of 170~273 K.However,for two specimens with different types of defects,in the measurement data below 170 K,a difference in the positron trapping ability of the Ag precipitates in the sample was observed.With the decrease of the measurement temperature,both the positron lifetime and it’s intensity of the Ag precipitates in the quenched specimens begin to stabilize and lose their dependence on temperature.In the measurement below 170 K,the precipitating ability of the Ag precipitates in the deformed sample still has a strong temperature dependence,but the change amplitude is gradually weakening.In the end,when the measurement temperature increased to around room temperature(273~293 K),more and more positrons escaped from the Ag precipitate,gradually transitioned back to the free state or trapping by other deep traps,and lost the temperature dependence.