Fatigue characterization of flowformed A356-T6

Matthew J Roy,Daan M Maijer,Jianbin Zhao,J.Y Buffière,F Morel,Y Nadot,M Brune

doi:10.1051/matecconf/20141203001

Matthew J Roy, Daan M Maijer + Show 5 more

Open Access

https://doi.org/10.1051/matecconf/20141203001

Copy DOI

Abstract

Flowforming is an incremental rotary forming technology consisting of deforming a cylindrical workpiece through contact between a roller and a rotating mandrel. This process delivers significant local compressive plastic strain to the workpiece. The effects on fatigue resilience of a common aluminum foundry alloy (A356) processed in this manner at an elevated temperature has been shown to improve post heat treatment. Fatigue properties of material processed with a standard heat treatment following casting is compared to material which has been cast and flowformed to varying degrees and then heat treated. Flowformed material with varying degrees of rotary deformation have been tested. Endurance limits have been found to be generally governed by porosity and maximum principal stress for high cycle fatigue on undeformed material. Fatigue properties have been quantified employing stress-life relationships derived from uniaxial fatigue tests. A 30% increase in the high-cycle endurance limits of flowformed compared to non-deformed material has been observed and is linked to the extent of deformation. Fractographic examination shows that this increase in endurance limit can be attributed primarily to the mitigation of porosity. Microstructural changes due to processing appear to be a secondary factor.

Highlights

Forging cast aluminium components is a relatively expensive manufacturing process that can improve mechanical properties
The results of the fatigue testing show that there is an appreciable improvement in flowformed material over undeformed post-heat treatment
The improvement was quantified by fitting Basquin relationships (b = 0.17) through data from both commercially and experimentally formed material

Summary

Introduction

Forging cast aluminium components is a relatively expensive manufacturing process that can improve mechanical properties. Fatigue properties of material processed with a standard heat treatment following casting is compared to material which has been cast and flowformed to varying degrees and heat treated. Flowformed material with varying degrees of rotary deformation have been tested.

Results

Conclusion