文章信息/Info

Title:

Atomic Resolution Study on the Effect of Zr Minor Addition on the Microstructure and Mechanical Properties of a Magnesium Alloy

文章編號(hào):

1674-3962(2023)03-0185-13

作者:

王威振; 周信哲; 楊志卿; 葉恒強(qiáng)

（1. 中國科學(xué)院金屬研究所 沈陽材料科學(xué)國家研究中心，遼寧 沈陽 110016） （2. 季華實(shí)驗(yàn)室，廣東 佛山 528200）

Author(s):

WANG Weizhen1; 2;  ZHOU Xinzhe1;  YANG Zhiqing2;  YE Hengqiang2

(1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science,Shenyang 110016, China) (2. Ji Hua Laboratory, Foshan 528200, China)

關(guān)鍵詞:

鎂合金; 微觀結(jié)構(gòu); 微合金化; 強(qiáng)化; 透射電子顯微術(shù)

Keywords:

magnesium alloys;  microstructure;  microalloying;  strengthening;  transmission electron microscopy

分類號(hào):

TG146.22;TN16

DOI:

10.7502/j.issn.1674-3962.202110028

文獻(xiàn)標(biāo)志碼:

A

摘要:

微量Zr的添加不僅能夠細(xì)化鎂合金的晶粒，改善鑄造性能，還會(huì)影響鎂合金在熱處理過程中微觀結(jié)構(gòu)的演變。利用多種電子顯微學(xué)技術(shù)系統(tǒng)研究了Zr微合金化影響Mg-Zn-Nd鎂合金力學(xué)性能和微觀結(jié)構(gòu)演變的機(jī)理。研究表明，含有微量Zr的Mg-2.7Nd-0.6Zn-0.5Zr鎂合金經(jīng)798 K固溶處理后，大量納米Zn-Zr相的析出顯著提升了該合金的顯微硬度。在系列微束電子衍射分析的基礎(chǔ)上，結(jié)合多方向原子分辨率結(jié)構(gòu)和成分分析，確定了這些納米Zn-Zr相為簡(jiǎn)單四方結(jié)構(gòu)的Zn2Zr3相（空間群：P42/mnm，a=b=0.761 nm, c=0.682 nm），并重構(gòu)出其原子構(gòu)型。此外，研究結(jié)果還表明固溶處理過程中形成的納米尺寸Zn2Zr3相，降低了基體中Zn元素的含量，顯著提升了強(qiáng)化效果較好的柱面析出相β1-Mg3Nd的比例，進(jìn)而提高了合金峰時(shí)效后的強(qiáng)度。研究結(jié)果豐富了Zr影響鎂合金微觀結(jié)構(gòu)和力學(xué)性能機(jī)理的研究。

Abstract:

The effect of Zr addition on microstructures and their evolution during heat treatments of a kind of Mg-Zn-Nd alloy was studied using various electron microscopy techniques. The minor addition of Zr not only provid heterogenous nucleation sites to refine grain sizes of Mg during solidification, but also influence microstructural evolution upon solution treatment and aging. Zn2Zr3 precipitates were formed in Mg-2.7Nd-0.6Zn-0.5Zr (wt%) during solution treatment at 798 K, inducing remarkable hardness increment of the alloy. The atomic structure of nanometer Zn-Zr precipitates is determined by combining tilt series of micro-beam electron diffraction with atomic resolution imaging and chemical measurement. The stoichiometry of the Zn-Zr precipitates is Zn2Zr3 with a primitive tetragonal structure (space group P42/mnm, a=b=0.761 nm, c=0.682 nm). Moreover, decrease in Zn concentration in Mg matrix due to the formation of Zn2Zr3 precipitates increased the density ratio of β1-Mg3Nd prismatic rod precipitates to γ″-Mg7(Nd, Zn)3 basal plates in peak aged samples. Our results may shed light on optimization of microstructures and mechanical properties of Mg alloys with Zr addition. Our present finding shed new light on the role of Zr micro-alloying in microstructures and mechanical properties of Mg alloys.