Grain control of Ni-based alloy 690 and its effect on mechanical properties

doi:10.13251/j.issn.0254-6051.2020.01.040

Abstract

Abstract: The effects of C content on grain growth and annealing twins of alloy 690 with different C contents were studied. The results show that within the range of 0.011%-0.028%, the change of C content significantly affects the grain growth process of the alloy 690, and its average grain size gradually decrease with the increase of C content. Especially when C content is between 0.020% and 0.028%, the grain refinement effect of C content is more significant. The grain boundary volume fraction of ∑3 ⁿ (n=1, 2, 3) increases first and then decreases with the increase of C content in the alloy structure. The content of C in the alloy of about 0.020% has a higher distribution of the grain boundary volume fraction of ∑9 and ∑27. On this basis, the alloy containing 0.02%C is selected to explore the quantitative relationship between the grain sizes and mechanical properties of the alloy caused by the change of solid solution treatment temperature was further discussed. The influence of grain refinement on the mechanical strength of alloy 690 follows the Hall-Petch relationship of the dislocation pile-up model. Moreover, it is found by fitting that the k _T value of the strengthening coefficient of tensile strength (18.95 MPa·mm ^1/2 ) is smaller than the k _y value of the strengthening coefficient of yield strength (23.67 MPa·mm ^1/2 ), and the grain refinement has a higher strengthening effect on the yield strength than the tensile strength. The strength increment of solute elements caused by solid solution strengthening is 243 MPa, while that caused by grain refinement is 157-7 MPa. The main strengthening mechanism of alloy 690 is solid solution strengthening mechanism.

Key words: alloy 690, carbon content, grain size, tensile properties, Hall-Petch relationship, solid solution strengthening, grain boundary strengthening

CLC Number:

TG146.1

Liu Zhe, Feng Han, Zheng Wenjie, Song Zhigang, Zhu Yuliang, Gao Peng. Grain control of Ni-based alloy 690 and its effect on mechanical properties[J]. HTM, 2020, 45(1): 203-209.

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