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首页> 外文期刊>Materials Science and Engineering >Abnormal flow behavior and necklace microstructure of powder metallurgy superalloys with previous particle boundaries (PPBs)
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Abnormal flow behavior and necklace microstructure of powder metallurgy superalloys with previous particle boundaries (PPBs)

机译：具有先前粒子边界（PPB）的粉末冶金高温合金的异常流动行为和项链显微组织

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摘要

Powder metallurgy (P/M) has been introduced as an innovative process to manufacture high performance components with fine, homogenous and segregation-free microstructure. Unfortunately, previous particle boundary (PPB) precipitated during the powder metallurgy process. Since undesirable PPB is detrimental to mechanical properties, hot extrusion or/and isothermal forging are needed. In present research, isothermal compression tests were conducted on P/M FGH4096 superalloys with typical PPBs. Abnormal flow behavior during high-speed deformation has been quantitatively investigated. Caused by the competition mechanism between work-hardening and dynamic-softening, abnormal flow behaves typical four stages (viz., work-hardening, stable, softening and steady). Microstructure observation for hardening or/and softening mechanism has been investigated. Meanwhile, necklace microstructure was observed by scanning electron microscope, and the grain fraction analysis was performed by using electron backscatter diffraction. Transmission electron microscopy was used for characterizing the boundary structure. Necklace microstructural mechanism for processing P/M superalloys has been developed, and the dynamic recrystallization model has also been conducted. Bulge-corrugation model is the primary nucleation mechanism for P/M superalloys with PPBs. When PPB is entirely covered with new grains, necklace microstructure has formed. Bulge-corrugation mechanism can repeatedly take place in the following necklace DRX.
机译：粉末冶金（P / M）作为一种创新工艺而被引入，用于制造具有精细，均匀且无偏析微观结构的高性能部件。不幸的是，在粉末冶金过程中，先前的颗粒边界（PPB）沉淀了。由于不期望的PPB不利于机械性能，因此需要热挤压或/和等温锻造。在目前的研究中，对具有典型PPB的P / M FGH4096高温合金进行了等温压缩试验。定量研究了高速变形过程中的异常流动行为。由于工作硬化和动态软化之间的竞争机制，异常流动表现为典型的四个阶段（即工作硬化，稳定，软化和稳定）。研究了硬化或软化机理的显微组织观察。同时，通过扫描电子显微镜观察项链的微观结构，并通过电子背散射衍射进行晶粒分数分析。透射电子显微镜用于表征边界结构。研究了加工P / M高温合金的项链微观结构机理，并建立了动态​​再结晶模型。凸起波纹模型是具有PPB的P / M高温合金的主要成核机理。当PPB完全被新颗粒覆盖时，就形成了项链的微观结构。在下面的项链DRX中，凸起的波纹机制会反复发生。

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