
Li含量对Al-Mg-Si合金时效析出行为的影响
杨晓琨, 熊柏青, 李锡武, 闫丽珍, 李志辉, 张永安, 李亚楠, 温凯
材料工程 ›› 2021, Vol. 49 ›› Issue (6) : 100-108.
Li含量对Al-Mg-Si合金时效析出行为的影响
Effect of Li content on ageing precipitation behavior of Al-Mg-Si alloy
采用透射电镜研究Li含量对Al-3.0Mg-0.6Si合金时效析出行为的影响,分析不同Li含量合金在170 ℃人工时效过程中析出相的演化与分布。结果表明:Li元素的添加改变了Al-3.0Mg-0.6Si合金的时效析出行为。添加2.15%(质量分数,下同)Li的合金,球状的δ'-Al3Li相成为晶内优先析出相,而针状的β″-Mg2Si相在时效后期阶段才逐渐析出,并在时效192 h后形成了明显的球状δ'相加针状β″相的双相析出。而添加3.12%Li的合金在所观察的时效阶段内均未发现有β″相析出。另外,未发现含Li合金晶界位置有析出相存在,晶界附近是无沉淀析出带(δ'-PFZs)和δ'相。在时效100 h后发现添加2.15%Li的合金在δ'-PFZ区域有针状β″相析出。添加2.15%Li的合金δ'-PFZ的半宽尺寸和增长速率均大于2.68%,3.12%Li添加量的合金。
The effect of Li content on the ageing precipitation behavior of Al-3.0Mg-0.6Si alloy was investigated by transmission electron microscopy. The evolution and distribution of the precipitation phases in alloys with different Li contents during the artificial ageing at 170 ℃ were analyzed. The results show that the addition of Li changes the ageing precipitation behavior of Al-3.0Mg-0.6Si alloy.In the alloy with 2.15%(mass fraction) Li addition, the spherical δ'-Al3Li phases are formed first in grain interiors, while the needle-shaped β″-Mg2Si phases gradually precipitate at the later ageing stage. After ageing for 192 h, there are obviously dual phase precipitation of spherical δ' phase and needle-shaped β″ phase formed.However, β″ phase precipitation is not found in the alloy with 3.12%Li addition during the observed ageing stage. In addition, there are no precipitation phases at the grain boundaries of the Li-containing alloys, and the precipitate-free zones (δ'-PFZs) and δ' phase are found nearby the grain boundaries. After ageing for 100 h, the alloy with 2.15%Li addition precipitates needle-shaped β″ phase in the δ'-PFZs regions. Both the half width size and growth rate of the δ'-PFZs in the alloy with 2.15%Li addition are greater than that of 2.68%, 3.12%Li alloys.
Al-Li合金 / Al-Mg-Si合金 / 析出相 / 无沉淀析出带 / 显微组织 {{custom_keyword}} /
Al-Li alloy / Al-Mg-Si alloy / precipitation phase / precipitate-free zone / microstructure {{custom_keyword}} /
表 1 实验所用合金化学成分(质量分数/%)Table 1 Chemical compositions of the experimental alloys (mass fraction/%) |
Alloy | Li | Mg | Si | Fe | Al |
1# | 0.00 | 3.12 | 0.60 | 0.016 | Bal |
2# | 2.15 | 3.08 | 0.58 | 0.012 | Bal |
3# | 2.68 | 3.16 | 0.57 | 0.014 | Bal |
4# | 3.12 | 3.10 | 0.61 | 0.017 | Bal |
图 3 合金在170 ℃时效100 h(1)和192 h(2)后晶内析出相的TEM组织照片及衍射花样(B=[001])(a)2#; (b)3#; (c)4# Fig.3 TEM images and SAED patterns of the intragranular precipitates in alloys aged at 170 ℃ for 100 h (1) and 192 h (2), respectively (B=[001]) (a)2#; (b)3#; (c)4# |
图 5 合金在170 ℃时效8 h后晶界位置及附近无沉淀析出带(δ′-PFZs)的TEM组织照片(a)1#; (b)2#; (c)3#; (d)4# Fig.5 TEM images of the grain boundaries and δ′-PFZs in alloys aged at 170 ℃ for 8 h (a)1#; (b)2#; (c)3#; (d)4# |
图 6 合金在170 ℃时效48 h后晶界位置及附近无沉淀析出带(δ′-PFZs)的TEM组织照片(a)1#; (b)2#; (c)3#; (d)4# Fig.6 TEM images of the grain boundaries and δ′-PFZs in alloys aged at 170 ℃ for 48 h (a)1#; (b)2#; (c)3#; (d)4# |
表 2 合金在170 ℃时效不同时间后的析出相及其分布Table 2 Precipitates and distribution of the alloys aged at 170 ℃ for different time |
Alloy | 8 h | 48 h | 100 h | 192 h | |||||||||||
GI | NGB | PFZ/nm | GI | NGB | PFZ/nm | GI | NGB | PFZ/nm | GI | NGB | PFZ/nm | ||||
1# | β″ | β″ | 22.4 | β′ | β′ | 30.4 | |||||||||
2# | δ′ | δ′ | 29.4 | δ′+β″ | δ′ | 125.3 | δ′+β″ | δ′+β″ | 207.1 | δ′+β″ | δ′+β″ | 242.9 | |||
3# | δ′ | δ′ | 28.2 | δ′ | δ′ | 118.8 | δ′+β″ | δ′ | 142.9 | δ′+β″ | δ′ | 183.4 | |||
4# | δ′ | δ′ | 26.9 | δ′ | δ′ | 112.5 | δ′ | δ′ | 128.6 | δ′ | δ′ | 175.4 |
表 3 含Li合金在170 ℃时效不同时间后δ′析出相数量密度统计结果Table 3 Number density statistic results of δ′ precipitation in the Li-containing alloys aged at 170 ℃ for different time |
Alloy | Number density/104m-2 | |||
8 h | 48 h | 100 h | 192 h | |
2# | 7.0 | 4.9 | 3.1 | 1.4 |
3# | 8.6 | 6.0 | 4.4 | 2.3 |
4# | 11.2 | 7.3 | 5.5 | 3.0 |
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