Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 836, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2020.154689
Keywords
Mg-Al-Ca alloy; Mn addition; Extrusion; Tensile properties; Nano-precipitates
Categories
Funding
- National Natural Science Foundation of China [51771062, 51971076]
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Effects of trace manganese (Mn) contents (0.1 wt% and 0.3 wt%) on mechanical properties and microstructure of the Mg-5.5Al-3Ca wt.% alloy were systematically investigated. By addition of 0.3 wt% Mn, the yield strength of the as-extruded alloy is significantly increased from 366 MPa to 402 MPa. The ascast alloys show a dendritic structure consists of a-Mg and (Mg, Al)(2)Ca phases. Mn addition leads to the formation of Al8Mn5 phase, but has no refining effect on the microstructure of the as-cast alloys. The as-extruded Mg-5.5Al-3Ca-xMn alloys exhibit a bimodal grain structure composed of dynamic recrystallized (DRXed) fine grains and coarse unDRXed grains. Compared with Mn free alloy, nano-scale Mg2Ca particles with a smaller diameter and higher number density are precipitated in the DRXed regions with 0.1Mn and 0.3Mn addition. These Mg2Ca particles are more effective in dispersion strengthening and grain growth inhibiting, which is considered to be the main reason for the increment on yield strength by Mn addition. Based on the thermaldynamic calculation and experimental results, the thermal stability and formation mechanism of the Mg2Ca precipitates were discussed. (C) 2020 Elsevier B.V. All rights reserved.
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