Homogenization treatment and microstructure evolution of Al-2.4Cu-1.3Li alloy micro-alloyed with Yb

doi:10.13251/j.issn.0254-6051.2023.02.020

Abstract

Abstract: Microstructure evolution of the Al-2.4Cu-1.3Li-(Yb) alloys during homogenization was analyzed by means of SEM, EDS, DSC and XRD measurements. The SEM observations show obvious dendrite in the as-cast alloys with the average dendrite spacing of 45±6 μm(Al-Cu-Li alloy) and 43±7 μm(Al-Cu-Li-Yb alloy), respectively. The morphology of primary phase is block or strip-like with 2.8% (Al-Cu-Li alloy) and 2.2% (Al-Cu-Li-Yb alloy) in relative ratio of area in SEM images. EDS and XRD results show that primary phases include mainly several types of Al-Cu-(Li) phases and Al₈Cu₄Yb phase additionally in case of the Al-Cu-Li-Yb alloy. Based on the DSC and homogenization kinetic analysis, the homogenization treatment is determined to be 500 ℃×12 h for remove the dendrite segregation. The corresponding SEM images of the specimens after homogenization treatment demonstrate that the retained phases are gathered tiny spheres of AlCuFe phases and/or skeletal-like Al₈Cu₄Yb phase, with the area fraction decreasing to 0.93% (Al-Cu-Li alloy) and 0.76% (Al-Cu-Li-Yb alloy), respectively. In order to dissolve more Yb to the matrix, a two-step homogenization treatment for the Al-Cu-Li-Yb alloy is determined experimentally to be 500 ℃×12 h+530 ℃×12 h. The SEM analysis showes the relative ratio of area of retained phases reduces to 0.53%. The morphology is the same as that of one-step homogenization annealing.

Key words: Al-Cu-Li alloy, Yb microalloying, homogenization, microstructure

CLC Number:

TG166.3

Zheng Zhi, Gao Kunyuan, Wen Shengping, Huang Hui, Wu Xiaolan, Wei Wu, Nie Zuoren. Homogenization treatment and microstructure evolution of Al-2.4Cu-1.3Li alloy micro-alloyed with Yb[J]. Heat Treatment of Metals, 2023, 48(2): 131-137.

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