Abstract Cu precipitates in steels can lead to significant changes of mechanical behavior. However, most investigations focus on the influence of these precipitates on hardness, whereas the effects on quasi-static deformation behavior and cyclic properties remain unclear. Therefore, in the present work the deformation behavior of Cu alloyed steels with two different carbon contents, 0.005 and 0.2 wt%, was analyzed in tensile as well as fatigue tests. To characterize the influence of different precipitation states, various heat treatments were performed. The heat treatment parameters were chosen based on results obtained with the short-time procedure PhyBaLCHT, which is based on cyclic indentation tests and enables the determination of microhardness and cyclic hardening potential. The results reveal that a higher C content increases hardness, decreases cyclic hardening potential and leads to generally higher tensile strength. However, only at a shorter aging time does a higher C content increase fatigue strength, whereas at a longer aging time both steel variants show comparable fatigue lifetimes, despite the significantly higher hardness and tensile strength of the steel with higher carbon content. This can be explained with the higher cyclic hardening potential of the lower carbon steel, leading to an improved fatigue lifetime. Additionally, it could be shown for both steels that an increase of cyclic hardening potential, caused by longer aging times and different precipitation states of Cu, can be associated with increased fatigue strength. However, for an overall assessment of a material’s mechanical properties, both, hardness and cyclic hardening potential have to be considered.

中文翻译：

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Cu的不同析出状态对不同含碳量Cu合金钢准静态和循环变形行为的影响

摘要 钢中的铜析出物会导致机械性能的显着变化。然而，大多数研究集中在这些析出物对硬度的影响上，而对准静态变形行为和循环性能的影响仍不清楚。因此，在目前的工作中，在拉伸和疲劳试验中分析了具有两种不同碳含量，0.005 和 0.2 wt% 的 Cu 合金钢的变形行为。为了表征不同沉淀状态的影响，进行了各种热处理。热处理参数是根据短时程序 PhyBaLCHT 获得的结果选择的，该程序基于循环压痕测试，能够确定显微硬度和循环硬化潜力。结果表明，较高的 C 含量会增加硬度，降低循环硬化潜力并导致通常更高的拉伸强度。然而，只有在较短的时效时间下，较高的 C 含量才能提高疲劳强度，而在较长的时效时间下，两种钢变体都表现出相当的疲劳寿命，尽管具有较高碳含量的钢的硬度和抗拉强度明显更高。这可以通过低碳钢的更高循环硬化潜力来解释，从而延长疲劳寿命。此外，这两种钢都可以证明，由较长的时效时间和不同的 Cu 析出状态引起的循环硬化潜力的增加可能与疲劳强度的增加有关。然而，对于材料机械性能的整体评估，必须同时考虑硬度和循环硬化潜力。