Effects of Different Microstructure on Strengthening Mechanism and Hardening Mechanism in Peak-Aged Mg–14Gd–0.2Sn Alloy

IF 3.3 3区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Metals and Materials International Pub Date : 2024-08-30 DOI:10.1007/s12540-024-01792-9

Boshu Liu, Kaiqiang Cao, Rongguang Li, Yuehong Zhang, Hang Zhang, Shanshan Li, Sha Sha

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Abstract

A bimodal-grained microstructure is formed in the Mg–14Gd–0.2Sn alloy extruded with a small extrusion ratio of 7 (E7 alloy), containing a large number of fine dynamic recrystallized (DRXed) grains with an average size of ~ 1.11 μm. In comparison, a much higher proportion of DRXed microstructure (~ 90%) with a coarser grain size of ~ 5.85 μm is formed in the alloy extruded with a large ratio of 16 (E16 alloy). The lower actual temperature during extrusion of the E7 alloy increases the supersaturation degree of α-Mg solid solution matrix, and induces a higher volume fraction of dynamic precipitates (β-Mg₅Gd) compared with the E16 alloy. After aging, the E7-A alloy exhibits a stronger precipitation strengthening effect with a peak-aged yield strength (YS) of 405 MPa. The YS of the E7-A alloy presents a remarkable improvement of 88 MPa compared with that of the E16-A alloy, which is mainly related to finer DRXed grains and stronger texture. In contrast, the hardness increment of the E16-A alloy is higher than that of the E7-A alloy, and the peak hardness of the E16-A alloy is comparable to that of the E7-A alloy. Although the high density of precipitates in the E16-A alloy contributes to a strong aging hardening response, the weaker precipitation strengthening effect of the E16-A alloy is mainly attributed to the activation of twinning in coarser grains with a weaker texture.

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不同显微组织对峰值时效 Mg-14Gd-0.2Sn 合金强化机制和硬化机制的影响

在挤压比为 7 的小挤压比 Mg-14Gd-0.2Sn 合金（E7 合金）中形成了双峰微观结构，其中包含大量平均尺寸约为 1.11 μm 的细小动态再结晶（DRXed）晶粒。相比之下，在大比例为 16 的挤压合金（E16 合金）中，形成的 DRX 化微观结构比例要高得多（约 90%），晶粒尺寸较粗，约为 5.85 μm。与 E16 合金相比，E7 合金挤压过程中较低的实际温度增加了 α-Mg 固溶体基体的过饱和程度，并诱发了较高体积分数的动态沉淀物（β-Mg5Gd）。时效后，E7-A 合金表现出更强的沉淀强化效果，其时效屈服强度（YS）峰值为 405 兆帕。与 E16-A 合金相比，E7-A 合金的屈服强度显著提高了 88 兆帕，这主要与更细的 DRX 化晶粒和更强的质地有关。相比之下，E16-A 合金的硬度增量高于 E7-A 合金，且 E16-A 合金的峰值硬度与 E7-A 合金相当。虽然 E16-A 合金中高密度的析出物有助于产生较强的时效硬化响应，但 E16-A 合金较弱的析出强化效果主要是由于较粗晶粒中孪晶的活化和较弱的质地造成的。

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来源期刊

Metals and Materials International 工程技术-材料科学：综合

CiteScore

7.10

自引率

8.60%

发文量

197

审稿时长

3.7 months

期刊介绍： Metals and Materials International publishes original papers and occasional critical reviews on all aspects of research and technology in materials engineering: physical metallurgy, materials science, and processing of metals and other materials. Emphasis is placed on those aspects of the science of materials that are concerned with the relationships among the processing, structure and properties (mechanical, chemical, electrical, electrochemical, magnetic and optical) of materials. Aspects of processing include the melting, casting, and fabrication with the thermodynamics, kinetics and modeling.