Microstructural evaluation and mechanical properties of 7075 aluminum alloy prepared by controlled diffusion solidification

• Published in: China foundry Vol. 16; no. 4; pp. 238 - 247
• Main Authors: Yang, Xiong, Li, Yuan-dong, Luo, Xiao-mei, Zhou, Hong-wei, Cai, Qi-yong, Li, Ming, Ma, Ying
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.07.2019; Foundry Journal Agency; State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China%State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China; Key Lab of Non-ferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China
• Subjects: Alloys; Aluminum (Metal); Aluminum alloys; Aluminum plate; Aluminum sheet; Analysis; Electron microscopy; elongation; Engineering; eutectic phase; Grain boundaries; Machines; Manufacturing; Materials Engineering; Mechanical properties; Metallic Materials; Microscopy; Porosity; primary α-Al phase; Processes; Research & Development; solute atoms; Specialty metals industry; tensile strength; Zinc (Metal); Zinc compounds; eutectic phase; tensile strength; elongation; primary α-Al phase; TG146.21; solute atoms
• ISSN: 1672-6421; 2365-9459; 1672-6421
• DOI: 10.1007/s41230-019-9059-9

In the present work, 7075 aluminum alloy (Al-Zn-Mg-Cu) was produced by both conventional casting (CC) and controlled diffusion solidification (CDS) methods. Each sample was subjected to different heat-treatment conditions: as-cast, T4, and T6; and their microstructural and mechanical properties were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). It was found that CDS promoted the formation of non-dendritic primary α-Al phase and reduced shrinkage porosity, thus resulting in improved mechanical properties. In addition, the eutectic phase of the CDS samples mainly consisted of T (Al-Zn-Mg-Cu) phase, which manifested a well-developed lamellar eutectic structure. However, in the CC samples, the T (Al-Zn-Mg-Cu) phase was composed of rod-like eutectics. Moreover, the θ (Al 2 Cu) eutectic contents in the CC samples were greater than those in the CDS samples. Each element in the CC samples had an obvious change in the grain boundary, whereas the change in element content in the CDS samples was gradual. Therefore, the non-dendritic morphology of the primary phase and the presence of rod-like eutectics in the matrix of the CDS samples led to enhanced tensile strength and elongation under different heat treatment conditions.