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首页> 外文期刊>Materials Science and Engineering >Effect of heat-treatment on microstructural evolution and mechanical behaviour of severely deformed Inconel 718
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Effect of heat-treatment on microstructural evolution and mechanical behaviour of severely deformed Inconel 718

机译：热处理对严重变形的Inconel 718的组织演变和力学行为的影响

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摘要

Severe plastic deformation (SPD) techniques impose very high level of strains and it can enhance the strength of a material several folds. In the current work, Inconel 718 alloy was severely deformed by machining process resulting in inherently “bi-modal” grain size distribution consisting of sheared zone with nano-structured grains and moderately refined grain zone. Hardness of machined chips were found to be much higher than that of bulk and increased further upon giving heat-treatment because of precipitation of γ’’ and γ’ nano-precipitates. However, as with most severely deformed materials, ductility of the machined chip is known to be very low, primarily because of the presence of large fractions of dislocation-saturated nano-structured grains which hinder any more dislocation generation or movement. In this work, we gave short heat-treatment to these deformed samples at elevated temperature to ensue controlled recrystallization in the sheared zone. However, heat-treatment is also expected to result in coarsening of precipitates as well as the grains of the matrix. This phenomenon may, not only reduce the strength, but may also reduce the pinning ability of the precipitates which endow the microstructure with thermal stability. Hence, the specific objective of this work is to understand the interplay of grain boundary pinning and recrystallization, both of which occur at elevated temperatures. Short heat-treatment of the severely deformed samples was performed for 15min between 700°C to 900°C. It was found that temperatures up to 800°C do not lead to appreciable recrystallization, while 900°C heat-treatment can cause appreciable recrystallization, albeit, limited to the shear zone. Size of precipitates was also found to grow with increasing temperature, nonetheless, samples heat-treated at 900°C were found to be thermally stable with a good fraction of coincidence site lattice boundaries, low grain size and improved hardness.
机译：严重的塑性变形（SPD）技术会施加非常高的应变，并且可以将材料的强度提高几倍。在当前的工作中，Inconel 718合金在加工过程中发生了严重变形，从而导致固有的“双峰”晶粒尺寸分布，包括具有纳米结构晶粒的剪切区和适度细化的晶粒区。发现加工后的切屑的硬度远高于散装的切屑，并且由于γ'和γ'纳米沉淀的沉淀，经过热处理后硬度进一步提高。但是，与最严重变形的材料一样，加工后的切屑的延展​​性非常低，这主要是因为存在大量的位错饱和纳米结构晶粒，这些晶粒阻碍了位错的产生或移动。在这项工作中，我们对这些变形的样品在高温下进行了短暂的热处理，以确保在剪切区中进行受控的重结晶。然而，还预期热处理会导致沉淀物以及基体晶粒粗大化。这种现象不仅会降低强度，而且还会降低使微结构具有热稳定性的沉淀物的钉扎能力。因此，这项工作的具体目标是了解晶界钉扎和再结晶的相互作用，这两者都在高温下发生。在700°C至900°C之间对严重变形的样品进行15分钟的短时热处理。已经发现，高达800℃的温度不会导致明显的重结晶，而900℃的热处理可以引起明显的重结晶，尽管仅限于剪切区。还发现沉淀物的尺寸随着温度的升高而增长，尽管如此，发现在900°C热处理的样品具有一定的热稳定性，同时具有良好的重合点晶格边界，低晶粒度和改善的硬度。

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