Bending Behavior of a Wrought Magnesium Alloy Investigated by the In Situ Pinhole Neutron Diffraction Method

Wei Wu,Ke An,Harley Skorpenske,Matthew Frost,Dunji Yu,Alexandru Stoica

doi:10.3390/cryst8090348

Abstract

The tensile twinning and detwinning behaviors of a wrought magnesium alloy have been investigated during in situ four-point bending using the state-of-the-art high spatial resolution pinhole neutron diffraction (PIND) method. The PIND method allowed us to resolve the tensile twinning/detwinning and lattice strain distributions across the bending sample during a loading-unloading sequence with a 0.5 mm step size. It was found that the extensive tensile twinning and detwinning occurred near the compression surface, while no tensile twinning behavior was observed in the middle layer and tension side of the bending sample. During the bending, the neutral plane shifted from the compression side to the tension side. Compared with the traditional neutron diffraction mapping method, the PIND method provides more detailed information inside the bending sample due to a higher spatial resolution.

Highlights

The deformation behavior of magnesium (Mg) alloys has been investigated extensively in the past decades, due to its combined excellent mechanical properties and lightweight [1,2]
The hexagonal close-packed (HCP) crystalline structure of Mg allows a limited number of slip systems, resulting in poor formability of wrought Mg alloys at room temperature, which restricts its wide applications
We demonstrate a study on the deformation behavior of a wrought Mg alloy during four-point bending using the in situ high spatial resolution pinhole neutron diffraction (PIND) method

Summary

Introduction

The deformation behavior of magnesium (Mg) alloys has been investigated extensively in the past decades, due to its combined excellent mechanical properties and lightweight [1,2]. The hexagonal close-packed (HCP) crystalline structure of Mg allows a limited number of slip systems, resulting in poor formability of wrought Mg alloys at room temperature, which restricts its wide applications. It has been well known that Mg possesses two easy deformation systems, {00.2} basal slip and {10.2} tensile twinning (or extension twinning) [3,4,5,6]. The {10.2} tensile twinning can be activated by tension parallel to the c-axis and compression perpendicular to the c-axis, which results in a sudden reorientation of the matrix lattice, approximately 86.3◦ [7,8]. Tensile twinning provides a tensile strain along the c-axis, which is not achievable by basal . The detwinning process can be activated by a stress/strain reversal in twined grains [10,11]

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Results

Conclusion