A Study on Manufacturing Technique and Alloy Characteristics of Bronze Mirrors from Jeollanam-do Region in the Three Kingdoms Period

This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

Effect of Dendrite Fraction on the M23C6 Precipitation Behavior and the Mechanical Properties of High Cr White Irons

High Cr white irons with various fractions of primary dendrite have been prepared through the modification of their chemical composition. Increasing C and Cr contents decreased the primary dendrite fraction. Eutectic solidification occurred with the phase fraction ratio of austenite: M7C3 = 2.76:1. The measured primary dendrite fractions were similar to the calculated results. ThermoCalc calculation successfully predicted fractions of M7C3, austenite, and M23C6. Conventional heat treatment at high temperature caused a destabilization of austenite, releasing it’s solute elements to form M23C6 carbide. Precipitation of M23C6 during destabilization preferentially occurred within primary (austenite) dendrite, however, the precipitation scarcely occurred within austenite in eutectic phase. Thus, M23C6 precipitation by destabilization was relatively easy in alloys with a high fraction of primary dendrite.

Unidirectional crystallization and 3D structure of ternary four-component eutectic of B4C-NbB2-SiC system

Purpose. To investigate the laws of crystallization and formation of 3D morphology of ternary eutectics in system B4C-NbB2-SiC. Research methods. SEM (SE, BSE), РСМА (EDS, WDS), XRD. Results. The micro- and macro-morphology of eutectic colonies in alloys of the system NbB2-SiC-В4С formed during directional crystallization have been investigated. The obtained patterns are embodied in a 3D structural model of (B4C+NbB2+SiC) eutectic cell and from these result, a microscopic kinetics of crystallization of this cell was proposed. The continuity of eutectic phase dendrites from nucleation to the end of growth and inadequacy of ideas about eutectic as a mechanical mixture of small crystals of eutectic phases were shown. Scientific novelty. For the first time a 3D model of a three-phase 4-component eutectic cell of eutectic colony was built. For the first time the possibility of combined microscopic crystallization kinetics of a three-phase eutectics was revealed, including both paired cooperative microscopic kinetics of (SіC+ NbB2) growth and the kinetics of autonomous growth of the third eutectic phase B4C. Practical value. Revealing the pattern of micro and macrostructure formation of a three-phase eutectics, which was formed in the course of directional crystallization, opens up technological prospects for purposeful control of the structure and properties of eutectic alloy due to the change of micro and macro morphological constituents, including the method of modification.