退火处理Fe_(43)Co_(43)Hf_7B_6Cu_1非晶合金的正电子湮没研究

Investigation on annealed Fe_(43)Co_(43)Hf_7B_6Cu_1 amorphous alloy by positron annihilation spectroscopy

对熔体急冷法制备的Fe43Co43Hf7B6Cu1非晶合金进行了200,300,400和500℃保温30min的退火处理,用正电子湮没寿命谱、X射线衍射、穆斯堡尔谱等方法研究了退火后试样的结构及结构缺陷变化.结果表明,在非晶合金的制备态,正电子主要在非晶基体相空位尺寸的自由体积中湮没,湮没寿命τ1为158.4ps,强度I1≥85%,另外有11.9%(I2)的正电子被非晶中的微孔洞(空位团)所俘获,湮没寿命τ2为397ps.在200,300,400℃退火时,结构弛豫导致τ1连续下降,在400℃,τ1约149ps,I1下降到80.8%,τ2降为352.9ps,I2增加到18.0%;当退火温度升高至500℃,非晶发生晶化,产生新的正电子俘获中心,I2急剧增加达26.7%.

Amorphous Fe43Co43Hf7B6Cu1 alloy prepared by melt-spun technique were annealed at temperature 200 ℃ ,300 ℃ , 400 ℃ and 500 ℃ for 30 min. The structure and structural defects in annealed specimens were investigated by positron annihilation lifetime spectra,X-ray diffraction （XRD） and Mssbauer spectroscopy （MS）,etc. . The results show that in the as-quenched amorphous alloy,more than 85% of the positrons are localized at vacancy-sized free volumes in the amorphous based phase,annihilation lifetime τ1 = 158. 4 ps,and the other 11. 9% of positrons are trapped by microvoids, with lifetime τ2 = 397 ps. After annealing at temperature 200 ℃ ,300 ℃ and 400 ℃ for 30 min,the atomic short range diffusion will give rise to the migration and annihilation of vacancy-like defects. The major component τ1will be reduced continuously. The value of τ1will decrease to 149 ps at 400 ℃ ,their relative intensities I1 decreases and reaches 80. 8% . Meanwhile the annihilation lifetime of positrons in the microvoids τ2 will change from 353 ps to 364 ps,their relative intensities I2 are increased to 18. 0% . When annealed at temperature 500 ℃ for 30 min,new trapping centers of positrons are produced owing to the crystallization of amorphous phase,I2 increases drastically to 26. 7% .