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<p>This study examines the impact of heat treatment on the microstructure, pore distribution, and electrical and thermal properties of pure copper prepared by selective laser melting (SLM). SLM copper was subjected to various heat treatment temperatures ranging from 200 to 1000&#xa0;°C. The findings reveal that increasing heat treatment temperatures result in relative density decreasing from 99.8% in the as-built state to 99.4% due to small increase in porosity. Heat treatments in the range of 200 to 400&#xa0;°C lead to recovery in microstructure reducing low angle boundaries among grains. The electrical conductivity improves from 90.26 to 92.8% IACS, and thermal conductivity increases from 374 to 389 W/m·K along the building directions after treatment at 400&#xa0;°C. This work uniquely demonstrates the anisotropic thermal expansion behavior of SLM copper and reveals the role of high-temperature pore migration in causing a sharp decline in thermal conductivity at temperatures above 800&#xa0;°C. Additionally, a detailed correlation is established between recrystallization, the formation of high-angle grain boundaries, and the enhancement of electrical conductivity. By annealing at temperatures above 600&#xa0;°C, recrystallization and the formation of high-angle grain boundaries lead to the diffusion of pores to grain boundaries, increasing coefficient of thermal expansion. Pores migrating to grain boundaries result in the dropping of thermal conductivity to 342 W/m·K, while electrical conductivity increases to 99.8%% IACS due to a decrease in dislocation density and grain boundaries. The slight increase in pores results in adverse effect on thermal conductivity in annealing after overly high temperature treatments. Thermal expansion resulting from redistribution of pores further leads to change in the dimension of SLM Cu parts. These results indicate that heat treatment can markedly alter the properties of SLM-manufactured copper compared to traditionally fabricated copper. This study provides in-depth observations on dimensional stability and physical properties of the additive manufactured pure copper for industrial applications.</p>

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Heat Treatment-Induced Pore Migration and Conductivity Evolution in Additively Manufactured Copper

  • 期刊论文

  • 发表日期：

    2025年8月4日

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  • Wondayehu Yeshewas Alemu,
  • Guang-Jie Huang,
  • Chia-Wei Tseng,
  • Kuo-Chi Chiu,
  • Shufeng Yang,
  • Jhewn-Kuang Chen

摘要

This study examines the impact of heat treatment on the microstructure, pore distribution, and electrical and thermal properties of pure copper prepared by selective laser melting (SLM). SLM copper was subjected to various heat treatment temperatures ranging from 200 to 1000 °C. The findings reveal that increasing heat treatment temperatures result in relative density decreasing from 99.8% in the as-built state to 99.4% due to small increase in porosity. Heat treatments in the range of 200 to 400 °C lead to recovery in microstructure reducing low angle boundaries among grains. The electrical conductivity improves from 90.26 to 92.8% IACS, and thermal conductivity increases from 374 to 389 W/m·K along the building directions after treatment at 400 °C. This work uniquely demonstrates the anisotropic thermal expansion behavior of SLM copper and reveals the role of high-temperature pore migration in causing a sharp decline in thermal conductivity at temperatures above 800 °C. Additionally, a detailed correlation is established between recrystallization, the formation of high-angle grain boundaries, and the enhancement of electrical conductivity. By annealing at temperatures above 600 °C, recrystallization and the formation of high-angle grain boundaries lead to the diffusion of pores to grain boundaries, increasing coefficient of thermal expansion. Pores migrating to grain boundaries result in the dropping of thermal conductivity to 342 W/m·K, while electrical conductivity increases to 99.8%% IACS due to a decrease in dislocation density and grain boundaries. The slight increase in pores results in adverse effect on thermal conductivity in annealing after overly high temperature treatments. Thermal expansion resulting from redistribution of pores further leads to change in the dimension of SLM Cu parts. These results indicate that heat treatment can markedly alter the properties of SLM-manufactured copper compared to traditionally fabricated copper. This study provides in-depth observations on dimensional stability and physical properties of the additive manufactured pure copper for industrial applications.