Research On The Mechanical Property and Microstructure of Pre-Hardened Single Point Incremental Room Temperature Forming of the 2219 Aluminum Alloy

Abstract

Single point incremental forming is a flexible and fast sheet metal processing process without a die that is adapted to the processing of small parts in single pieces. Soft state (O state) high-strength aluminum alloy sheet is often used for single-point incremental forming, and then solution-quenching-aging heat treatment is carried out to obtain high strength (T6 state) after forming. However, the heat treatment will lead to poor precision, requiring repeated manual shape calibration, resulting in a long process with low efficiency and a high cost. This paper presents a novel pre-harden single point incremental room temperature forming process of the 2219 aluminum alloy. The sheet is first pre-aged to a hardened state, and after forming, high strength and high precision components can be obtained without further heat treatment. The tensile behavior of the pre-aged alloy is studied by tensile tests, the temperature during the forming process is characterized by thermal imaging, the mechanical properties after forming is evaluated by the hardness tester, the stress-strain and temperature evolution during the forming process are analyzed by numerical simulation, and the microstructure evolution during the process is characterized by transmission electron microscopy (TEM). The results show that the hardness of the parts obtained from this new process reaches up to 140 HV, which exceeds that of the traditional T6 state (125 HV). The large number of dislocations generated during single-point incremental forming not only increases the hardness but also lowers the precipitation temperature of the strengthening phase θ', and the frictional heat generated during the forming process promotes the large precipitation of the θ' phase. The process greatly improves the forming efficiency and ensures the mechanical properties, and it can be applied to the production of various parts.

Keywords: Pre-hardened single point incremental forming, Room temperature, Mechanical property, Microstructure