# Effect of Grain Size on Polycrystalline Copper Finish Quality of Ultra-Precision Cutting

## TL;DR

This paper studies how grain size in polycrystalline copper affects the quality of ultra-precision cutting, showing that smaller grains improve surface finish but require more energy.

## Contribution

The study introduces multiscale modeling combined with experiments to reveal process–structure–property relationships in copper machining.

## Key findings

- Refined grain structures lead to more uniform deformation and better surface finish with lower roughness.
- Fine grains increase cutting energy needs due to higher grain boundary density.
- Subsurface damage and cutting force behavior are influenced by grain size.

## Abstract

Polycrystalline copper optics are widely utilized in infrared systems due to their exceptional electrical and thermal conductivity combined with favorable machining characteristics. The grain size profoundly influences both surface quality consistency and fundamental material removal behavior during processing. This investigation employs multiscale numerical modeling to simulate nanoscale cutting processes in polycrystalline copper with controlled grain structures, coupled with experimental ultra-precision machining validation. Comprehensive analysis of stress distribution, subsurface damage formation, and cutting force evolution reveals that refined grain structures promote more homogeneous plastic deformation, resulting in superior surface finish with reduced roughness and diminished grain boundary step formation. However, the enhanced grain boundary density in fine-grained specimens necessitates increased cutting energy input. These findings establish critical process–structure–property relationships essential for advancing precision manufacturing of copper-based optical systems.