Effect of Forming-Die Temperature on Microstructure and Mechanical Properties of AA7075 Alloy During HFQ® Process

• Published in: Transactions of the Indian Institute of Metals 2021-03, Vol.74 (3), p.725-734
• Main Authors: Jiang, Y. F., Ding, H., Cai, M. H., Chen, Y., Liu, Y., Zhang, Y. S.
• Format: Article
• Language: English
• Subjects: Aging (metallurgy); Aluminum base alloys; Baking; Base metal; Chemistry and Materials Science; Corrosion and Coatings; Die forming; Forming dies; Hot forming; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Original Article; Precipitates; Tribology
• ISSN: 0972-2815; 0975-1645
• DOI: 10.1007/s12666-020-02146-w

Hot forming quenching-integrated process (HFQ ® ) has aroused widespread attention as a new stamping technology recently for producing complex-shaped structural parts. Forming-die temperature plays a critical role on tailoring the microstructure and mechanical properties of the final hot formed parts. In this paper, the HFQ ®  + pre-ageing (PA) + simulated baking (SB) process was used for AA7075 alloy to investigate the changes in microstructure and mechanical properties as a function of forming-die temperature ranging from 25 to 400 °C. The results show that the volume fraction of η ′ precipitates drops and part of η ′ phase becomes coarsened after HFQ ®  + PA + SB process with 25–200 °C forming dies, when compared with the base metal. As forming-die temperature ranges from 300 to 400 °C, a large number of η phase can be found. The overall mechanical properties of U-shaped parts were compared under various forming-die temperature. The forming-die temperature of 200 °C was selected where the AA7075 alloy U-shaped parts exhibit good combination of strength and ductility, i.e., the value of PSE being approximately 7534 MPa·%, which suits for the industry production.