The plastic flow of polycrystalline solids

TL;DR

This paper presents an analytical model of polycrystalline solid deformation, capturing plastic and superplastic regimes, with applications to nickel alloys and steels showing superior agreement with experimental data.

Contribution

It introduces a novel analytical model for polycrystalline deformation that does not rely on pre-existing cracks, improving upon previous theories.

Findings

Model accurately predicts plastic and superplastic behavior.

Excellent agreement with experimental data on nickel alloys.

Provides a new framework for understanding deformation without pre-existing flaws.

Abstract

A polycrystalline solid is modelled as an ensemble of random irregular polyhedra filling the entire space occupied by the solid body, leaving no voids or flaws between them. Adjacent grains can slide with a relative velocity proportional to the local shear stress resolved in the plane common to the two sliding grains, provided it exceeds a threshold. The local forces associated to the continuous grain shape accommodation for preserving matter continuity are assumed much weaker. The model can be solved analytically and for overcritical conditions gives two regimes of deformation, plastic and superplastic. The plastic regime, from yield to fracture, is dealt with. Applications to nickel superalloys and stainless steels give impressive agreement with experiment. Most work of the last century relies on postulating pre--existent cracks and voids to explain plastic deformation and fracture. The present model gives much better results.