Strengthening Mechanisms in NiAl Bronze: Hot Deformation by Rolling and Friction-Stir Processing

Sarath K. Menon,Frank A. Pierce,Brian P. Rosemark,Srinivasan Swaminathan,Keiichiro Oh-Ishi,Terry R. McNelley

doi:10.1007/s11661-012-1181-x

Abstract

Abstract Microstructures produced by isothermal hot rolling of a NiAl bronze material were evaluated by quantitative microscopy methods and parameters describing the contributions of precipitate dispersions, grain size, solute content, and dislocation density to the yield strengths of the individual constituents of microstructure were determined. Models for the strengths of the individual constituents were combined to predict the temperature dependence of the yield strength as a function of hot rolling temperature, and the prediction was found to be in good agreement with measured yield strengths. The models were applied to microstructures in a stir zone produced by multipass friction-stir processing (FSP) and, again, found to predict measured yield strengths with high accuracy. Such models may aid in assessing the role of microstructure gradients produced during FSP and other processes.

Highlights

GRADIENTS in strain, strain rate, and temperature during deformation processing may lead to gradients in microstructure that, in turn, affect material response during subsequent mechanical testing of as-processed material
The latter is the case for friction-stir processing (FSP), which is an allied technique of friction stir welding (FSW), a solid-state joining method developed at The Welding Institute.[1,2,3]
The following conclusions may be drawn from this investigation: 1. The hot rolling of NiAl bronze materials at temperatures above the eutectoid reversion reaction results in compatible deformation of the primary a and the b phases

Summary

Introduction

GRADIENTS in strain, strain rate, and temperature during deformation processing may lead to gradients in microstructure that, in turn, affect material response during subsequent mechanical testing of as-processed material. Assessing the role of such gradients in mechanical response can be facilitated by microstructure-based models of strength, especially when gradients are steep or when such gradients are an inherent feature of the deformation technique. The latter is the case for friction-stir processing (FSP), which is an allied technique of friction stir welding (FSW), a solid-state joining method developed at The Welding Institute.[1,2,3] In FSP, a rotating, nonconsumable cylindrical tool with a concentric projecting pin is pressed into a work piece surface. When the tool shoulder contacts the work piece surface the tool may be traversed across the surface to process the volume of material that is swept by the pin profile

Results

Discussion

Conclusion