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研究了软化和硬化材料表面喷丸应变层内的组织结构。结果表明,这种应变并不是一种简单的单凋塑性应变,而是循环塑性应变。循环应变使表层材料发生“循环硬化(或软化)”,与在应变疲劳中所发生的变化相类似。材料喷丸后发生循环硬化或软化,取决于材料的原始组织结构以及喷丸强度。对于软化材料,喷丸过程中发生循环硬化;而对于硬化材料(马氏体钢或时效马氏体钢),则首先发生循环软化,然后转为循环再硬化。试验表明,这种循环硬化(或软化)的性质取决于材料的亚晶粒尺寸,点阵畸变和位错密度。
The microstructure of the shot peening strain layer on softened and hardened materials was investigated. The results show that this kind of strain is not a simple plastic strain but a cyclic plastic strain. Cyclic strain causes the skin material to “cycle through (or soften)” similar to what happens in strain fatigue. Cyclic hardening or softening of the material after shot peening depends on the original structure of the material and shot peening strength. For softened materials, cyclic hardening occurs during shot peening, whereas for hardened materials (martensitic steel or aged martensitic steel), cyclic softening takes place first, then to cyclic hardening. Experiments have shown that the nature of this cyclic hardening (or softening) depends on the subgrain size, lattice distortion and dislocation density of the material.