Abstract

Abstract Two copper-based alloys were considered, Cu-1 pct Cr and Cu-0.7 pct Cr-1 pct Si-2 pct Ni. The thermal, electrical, and mechanical properties of these alloys are given in the paper and compared to pure copper and steel. The role of aging and precipitation kinetics in hardening of the alloys is discussed based upon the developed model. Results of plastometric tests performed at various temperatures and various strain rates are presented. The effect of the initial microstructure on the flow stress was investigated. Rheologic models for the alloys were developed. A finite element (FE) model based on the Norton–Hoff visco-plastic flow rule was applied to the simulation of forging of the alloys. Analysis of the die wear for various processes of hot and cold forging is presented as well. A microstructure evolution model was implemented into the FE code, and the microstructure and mechanical properties of final products were predicted. Various variants of the manufacturing cycles were considered. These include different preheating schedules, hot forging, cold forging, and aging. All variants were simulated using the FE method and loads, die filling, tool wear, and mechanical properties of products were predicted. Three variants giving the best combination of forging parameters were selected and industrial trials were performed. The best manufacturing technology for the copper-based alloys is proposed.

Highlights

  • THE tendency to increase strength-to-density ratio will be the main objective of research on materials processing for many years.[1]

  • On the basis of simulations of various manufacturing chains, two alternative technologies were selected for the industrial trials: (1) Hot forging followed by supersaturation annealing and aging and (2) Hot forging followed by cold forging with the reduction of 5 mm

  • Annealing twins are observed in the microstructure. Recapitulating this part of the research, it can be concluded that manufacturing of the CuCr products by hot forging followed by heat treatment composed of supersaturation annealing and aging obtains uniform hardness greatly exceeding the required value of 100 HV

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Summary

INTRODUCTION

THE tendency to increase strength-to-density ratio will be the main objective of research on materials processing for many years.[1]. There are, several examples of thermal or electrical applications which require a reasonably high level of strength in a material, which cannot be reached by pure copper.[3] This can be reached by precipitation strengthened alloys. Strain hardening and precipitation hardening are the most efficient ways by which the strength of the alloys may be improved Simultaneous use of both these mechanisms is of particular interest and it was the main objective of research in this work

COPPER-BASED ALLOYS
RHEOLOGICAL AND MICROSTRUCTURE EVOLUTION MODELS
Experiment
Experimental Results
Rheological Models
Microstructure Evolution Models
Precipitation Hardening
N dN dt
Finite Element Model
DESIGN OF THE MANUFACTURING CYCLE FOR FORGING OF THE Cu-BASED ALLOYS
Extrusion
Hot Forging
Microstructure Evolution
Cold Forging
Tool Wear An increased tool life is required for economical
Supersaturation Annealing and Aging
LABORATORY AND INDUSTRIAL TRIALS
Warm Forging
Industrial Forging
Precipitation and Supersaturation Annealing
CONCLUSIONS
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