Yield Point Phenomenon Induced by Twinning Accompanied by Abnormal Grain Growth in Fine-Grained Copper

Abstract

In this study, an equiaxed fine-grained copper specimen was fabricated by powder injection molding, followed by hot isostatic pressing. The specimen showed a yield point phenomenon with a Lüders-type deformation during a uniaxial tensile test. This study aimed to identify the cause of the yield point phenomenon in the fine-grained copper specimen. First, the Lüders band was designed to partially propagate within the gauge section through an interrupted uniaxial tensile test equipped with a digital image correlation system. The microstructures of the Lüders and non-Lüders band regions were compared by electron backscatter diffraction. It was observed that self-annealing was accelerated by the applied stress in the Lüders band region. Consequently, the microstructure of the Lüders band region transformed into a bimodal structure composed of fine grains and abnormally coarse grains containing numerous large twins. Identification of active twin variants in the abnormally coarse grains suggested that a significant tensile strain can be accommodated by this twinning. Based on these results, it was confirmed that the strain burst generated by the sudden occurrence of numerous large twins induces the yield point phenomenon in the fine-grained copper.

Review of “Integrated Computer-Aided Process Engineering Session in the International Symposium on Innovation in Materials Processing (ISIMP, 26–29 October 2021)”

“…The session focused on recent breakthroughs in scale-bridging simulations and characterization techniques for understanding, characterizing, and predicting the PSP relationships of newly developed materials at the laboratory and industrial levels. Eleven selected papers [47][48][49][50][51][52][53][54][55][56][57] were published in a special issue of Materials Transactions (Vol. 63, No.…”