Study on Corrosion Resistance of Friction Stir Welded LA81 Mg-Li Dual-Phase Alloy Joints

WANG Nan; WANG Shouwu; HUANG Xingliang; CHEN Changrui; CHEN Yuhua; HU Jie; JIANG Qing; ZHENG Min

doi:10.7512/j.issn.1001-2303.2025.11.01

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Study on Corrosion Resistance of Friction Stir Welded LA81 Mg-Li Dual-Phase Alloy Joints
Vol. 55, Issue 11, Pages: 1-9(2025)
Received：01 September 2025，

Revised：2025-09-15，

Published：20 November 2025
DOI： 10.7512/j.issn.1001-2303.2025.11.01
稿件说明：

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王楠，王守武，黄兴亮，等.LA81双相镁锂合金搅拌摩擦焊接头耐腐蚀性能研究［J］.电焊机，2025，55（11）：1-9. DOI： 10.7512/j.issn.1001-2303.2025.11.01.

WANG Nan, WANG Shouwu, HUANG Xingliang, et al.Study on Corrosion Resistance of Friction Stir Welded LA81 Mg-Li Dual-Phase Alloy Joints[J].Electric Welding Machine, 2025, 55(11): 1-9. DOI： 10.7512/j.issn.1001-2303.2025.11.01.

摘要

LA81镁锂合金因其轻质、高强度和减振性能，是航空航天轻量化的理想材料。本研究采用不同转速（475~1 180 r/min）与焊接速度（47.5~118 mm/min）对2 mm厚LA81镁锂合金进行搅拌摩擦焊接（Friction stir welding，FSW），探究FSW工艺参数对接头组织与耐蚀性能的影响，分析接头腐蚀机理与微观组织演变之间的关系。电化学测试表明，当搅拌头转速固定为475 r/min时，焊接速度为60 mm/min的试样耐腐蚀性最优，其自腐蚀电流密度降至2.4948×10

-4

μA/cm

，较母材（3.116 02×10

-4

μA/cm

）降低19.9%。微观表征分析表明：焊缝焊核区因动态再结晶形成细晶组织（晶粒尺寸

5 μm），腐蚀形貌以稀疏浅蚀坑为主；而热机械影响区晶粒粗大、β-Li相连续分布，发生显著晶间腐蚀与相界溶解。EDS结果显示腐蚀优先发生于β-Li相（富Li区），伴随Li

O等产物生成。长期浸泡试验表明：FSW焊缝在72 h内仍保持较完整表面，而母材在48 h即出现严重剥落腐蚀（蚀坑直径

70 μm）。FSW可通过细晶强化与双相分布优化显著提升LA81镁锂合金的耐腐蚀性能。

Abstract

LA81 Mg-Li alloy is an ideal material for aerospace lightweight applications due to its low density

high specific strength

and excellent damping capacity. In this study

friction stir welding (FSW) butt welding was performed on 2 mm-thick LA81 Mg-Li alloy plates using different tool rotational speeds (475-1 180 r/min) and welding speeds (47.5-118 mm/min). The aim was to investigate the influence of FSW parameters on the on the the microstructure and corrosion resistance of the joints

as well as to analyze the relationship between the corrosion mechanism and microstructural evolution. Electrochemical tests revealed that at a constant

tool rotational speeds of 475 r/min

the sample welded at a welding speed of 60 mm/min exhibited the highest corrosion resistance

with a corrosion current density of 2.494 8×10

-4

μA/cm

which is 19.9% lower than that of the base material (3.116 02×10

-4

μA/cm

). Microstructural analysis indicated that the weld nugget zone (WNZ) consisted of fine recrystallized grains (size

5 μm) resulting from dynamic recrystallization during FSW

which contributed to shallow and sparse corrosion pits. In contrast

the thermo-mechanically affected zone (TMAZ) exhibited coarse grains and continuous networks of β-Li phase

leading to pronounced intergranular corrosion and dissolution along phase boundaries. EDS results confirmed that corrosion initiated preferentially in the β-Li phases (Li-rich regions)

accompanied by the formation of corrosion products such as Li

O. Long-term immersion tests showed that FSW joints maintained relatively intact surfaces after 72 h

whereas the base metal suffered severe exfoliation corrosion with pit diameters exceeding 70 μm within 48 h. It is concluded that FSW significantly enhances the corrosion resistance of LA81 Mg-Li alloy through grain refinement and optimization of dual-phase distribution.

关键词

Keywords

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