Tribological Behavior and the Mild-Severe Wear Transition of Mg97Zn1Y2 Alloy with a LPSO Structure Phase.

Wei Sun,Jian An,Liang Li,Xihua Xuan

doi:10.3390/ma11040505

Abstract

Dry friction and wear tests were performed on as-cast Mg97Zn1Y2 alloy using a pin-on-disc configuration. Coefficients of friction and wear rates were measured as a function of applied load at sliding speeds of 0.2, 0.8 and 3.0 m/s. The wear mechanisms were identified in the mild and severe wear regimes by means of morphological observation and composition analysis of worn surfaces using scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Analyses of microstructure and hardness changes in subsurfaces verified the microstructure transformation from the deformed to the dynamically recrystallized, and properties changed from the strain hardening to dynamic crystallization (DRX) softening before and after the mild–severe wear transition. The mild–severe wear transition can be determined by a proposed contact surface DRX temperature criterion, from which the critical DRX temperatures at different sliding speeds are calculated using DRX dynamics; hence transition loads can also be calculated using a transition load model. The calculated transition loads are in good agreement with the measured ones, demonstrating the validity and applicability of the contact surface DRX temperature criterion.

Highlights

Mg97Zn1Y2 alloy has attracted a lot of attention due to its unique long-period stacking ordered (LPSO) structure phase [1,2]
The ingot had the dimensions of diameter 95 mm and length 200 mm, from which specimens of 8 mm diameter and 12 mm length were directly machined for measurements of hardness and compressive properties
The X-ray diffraction (XRD) peaks of the X-Mg12 ZnY phase in Figure 1 agree with those reported in as-cast and hot-rolled

Summary

Introduction

Mg97Zn1Y2 alloy has attracted a lot of attention due to its unique long-period stacking ordered (LPSO) structure phase [1,2]. The LPSO structure phase in Mg97Zn1Y2 alloy is typically an intermetallic compound X-Mg12 ZnY with a long-period 18 R modulated structure [3]. The RS/PM Mg97Zn1Y2 alloy demonstrates extraordinary mechanical properties at room and elevated temperatures, namely high yield strength above 600 MPa and elongation of 5% at room temperature and yield strength of 510 MPa at 150 ◦ C [4]. Mg97Zn1Y2 alloy displays other excellent characteristics, which makes it greatly different from those conventional magnesium alloys containing ordinary intermetallic compound phases. The LPSO phase exhibited a rather high thermal stability up to 500 ◦ C in an extruded Mg97Zn1Y2 alloy, which was proved by the unchanged

Methods

Results

Conclusion