<正> 正电子湮灭技术对材料的空位、位错等缺陷均十分灵敏,已广泛用于研究点阵缺陷及有关问题。由于塑性区内部塑性变形不均匀,故其内部缺陷密度分布亦是不均匀的,可能导致不均匀的正电子湮灭效应。本文尝试用正电子湮灭技术研究裂纹顶端塑性
Central cracked and single edge cracked α-Ti specimens were loaded up to different stress levels and cut into four test pieces after unloading. Both parameters, positron lifetime and Doppler broadening lineshape S parameters were measured in the plastic zone at the crack tip. The Doppler broadening lineshape S parameters were measured as a function of distance from the crack tip along the crack direction, It was found that the S parameters decrease monotonically along the crack direction until the boundary of the plastic zone is reached. The size of plastic zone estimated by the positron annihilation method seems to agree roughly with that obtained from that calculated by fracture mechanics.
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