Microstructural characterisation of artificially aged and service-exposed ASTM A204 Grade C steel reveals changes in the cementite particles of pearlite and microstructure. The ageing temperatures were chosen to be high enough to replicate the service degradation but below A c1 to avoid austenitisation in the inter-critical regime. Tensile testing of artificially aged materials shows a decrease in the ultimate tensile strength (UTS) along with an increase in elongation. On the other hand, service-exposed material resulted in an increase in UTS and a decrease in elongation. The softening of pearlite due to spheroidisation of cementite and segregation of alloying elements towards grain boundaries were responsible for the lower UTS of the artificially aged samples. Whereas, the increase in UTS in the service-exposed sample was attributed to the formation of nano-sized carbides inside ferrite grains, hence strengthening the steel matrix.

中文翻译：

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ASTM A204 C 级钢的暴露和人工时效显微组织和拉伸性能的差异

人工时效和服务暴露的 ASTM A204 C 级钢的微观结构表征揭示了珠光体和微观结构的渗碳体颗粒的变化。选择的时效温度足够高以复制服务退化，但低于 A c1 以避免在临界状态下奥氏体化。人工时效材料的拉伸测试显示极限拉伸强度 (UTS) 降低，同时伸长率增加。另一方面，服务暴露的材料导致 UTS 增加和伸长率降低。由于渗碳体球化和合金元素向晶界偏析导致珠光体软化是人工时效样品的 UTS 较低的原因。然而，