Microstructural Characterization of Nodular Ductile Iron

Springer, H K

关键词: DISTRIBUTION;    FLUCTUATIONS;    FRACTURES;    GRAPHITE;    IRON;    METALLOGRAPHY;    METRICS;    MICROSTRUCTURE;    NUCLEATION;    OPTICAL MICROSCOPY;    SHAPE;   

DOI  :  10.2172/1034481
RP-ID  :  LLNL-TR-522092
PID  :  OSTI ID: 1034481
Others  :  TRN: US201204%%28

学科分类：材料科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

The objective of this study is to quantify the graphite particle phase in nodular ductile iron (NDI). This study provides the basis for initializing microstructure in direct numerical simulations, as part of developing microstructure-fracture response models. The work presented here is a subset of a PhD dissertation on spall fracture in NDI. NDI is an ideal material for studying the influence of microstructure on ductile fracture because it contains a readily identifiable second-phase particle population, embedded in a ductile metallic matrix, which serves as primary void nucleation sites. Nucleated voids grow and coalesce under continued tensile loading, as part of the micromechanisms of ductile fracture, and lead to macroscopic failure. For this study, we used 2D optical microscopy and quantitative metallography relationships to characterize the volume fraction, size distribution, nearest-neighbor distance, and other higher-order metrics of the graphite particle phase. We found that the volume fraction was {Phi} = 0.115, the average particle diameter was d{sub avg} = 25.9 {mu}m, the Weibull shape and scaling parameters were {beta} = 1.8 and {eta} = 29.1 {mu}m, respectively, the (first) nearest neighbor distance was L{sub nn} = 32.4 {mu}m, the exponential coefficients for volume fraction fluctuations was A{sub {Phi}} = 1.89 and B{sub {Phi}} = -0.59, respectively. Based on reaching a coefficient-of-variation (COV) of 0.01, the representative volume element (RVE) size was determined to be 8.9L{sub nn} (288 {mu}m).