Effect of T6 Heat Treatment on Microstructure and Hardness of Nanosized Al2O3 Reinforced 7075 Aluminum Matrix Composites

• Main Authors: Peng-Xiang Zhang, Hong Yan, Wei Liu, Xiu-Liang Zou, Bin-Bing Tang
• Format: Article
• Language: English
• Published: MDPI AG 2019-01-01
• Series: Metals
• Subjects: Al2O3np/7075 composites; T6 heat treatment; microstructure; hardness; strengthening mechanism
• Online Access: http://www.mdpi.com/2075-4701/9/1/44

In this study, 7075 aluminum matrix composites reinforced with 1.5 wt.% nanosized Al2O3 were fabricated by ultrasonic vibration. The effect of T6 heat treatment on both microstructure and hardness of nanosized Al2O3 reinforced 7075 (Al2O3np/7075) composites were studied via scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy, and hardness tests. The Mg(Zn,Cu,Al)2 phases gradually dissolved into the matrix under solution treatment at 480 °C for 5 h. However, the morphology and size of Al7Cu2Fe phases remained unchanged due to their high melting points. Furthermore, the slenderness strips MgZn2 phases precipitated under aging treatment at 120 °C for 24 h. Compared to as-cast composites, the hardness of the sample under T6 heat treatment was increased ~52%. The strengthening mechanisms underlying the achieved hardness of composites are revealed.