Microstructure and Mechanical Strength of Attritor-Milled and Spark Plasma Sintered Mg-4Y-3Nd Alloy

Mária Zemková,Stanislav Šašek,Peter Minárik,Robert Král,Jan Dittrich,Michal Knapek

doi:10.3390/cryst10070574

Mária Zemková, Stanislav Šašek + Show 4 more

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https://doi.org/10.3390/cryst10070574

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Abstract

Gas-atomized powder of an Mg-4Y-3Nd magnesium alloy was attritor-milled at room temperature in an argon atmosphere for two time periods—1.5 and 5 h. Subsequently, the gas-atomized powder as well as both of the milled powders were spark plasma sintered at four temperatures, 400, 450, 500, and 550 °C, for 3 min. The effect of the milling on the powder particles’ morphology and the microstructure of the consolidated samples were studied by advanced microscopy techniques. The effect of the microstructural changes, resulting from the pre-milling and the sintering temperature, on the mechanical strength was investigated in compression along and perpendicular to the sintering load direction. Both the compression yield strength and ultimate compression strength were significantly affected by the grain size refinement, residual strain, secondary phase particles, and porosity. The results showed that attritor-milling imposed severe deformation to the powder particles, causing a significant grain size refinement in all of the consolidated samples. However, 1.5 h of milling was insufficient to achieve uniform refinement, and these samples also exhibited a distinctive anisotropy in the mechanical properties. Only a negligible anisotropy and superior yield strength were observed in the samples sintered from 5 h milled powder, whereas the ultimate strength was lower than that of the samples sintered from the gas-atomized powder.

Highlights

The classical preparation methods of metallic materials, such as casting, followed by extrusion and/or severe plastic deformation techniques, are capable of producing large volumes of the material, but the process is time-consuming and requires specific machinery
The present study focuses on one of the most commercially successful magnesium alloy systems—Mg-rare earth elements (RE)
The gas-atomized and attritor-milled powders of WN43 magnesium alloy were consolidated by the spark plasma sintering (SPS) technique

Summary

Introduction

The classical preparation methods of metallic materials, such as casting, followed by extrusion and/or severe plastic deformation techniques, are capable of producing large volumes of the material, but the process is time-consuming and requires specific machinery. The subsequent machining to prepare the final shapes results in significant material loss. Deformation-based processing techniques often cause the formation of a crystallographic texture, resulting in anisotropy in the material properties [1]. The modern powder metallurgy techniques may, provide significant reduction in the material preparation cost through a combination of fast throughput and limited waste. This holds, in particular, when (ultra) fine-grained materials need to be prepared

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