The effect of aging heat treatment on the formability and microstructure of the AA6063 tube in the rotary draw bending process

Abstract

This research delves into the impact of aging heat treatment on both the formability and microstructural characteristics of 6063 aluminum tubes when subjected to the rotary draw bending (RDB) procedure. To ascertain a heat treatment regimen that can yield desirable hardness and formability for the bending process, the tube was subjected to T3, T6, and annealing heat treatment cycles under diverse conditions and subsequently the tube's bendability was evaluated. The findings indicate that as temperature and dissolution time are raised, there is a corresponding rise in the extent of elliptical deformation, consequently resulting in higher hardness values. The research outcomes suggest that elevating both temperature and dissolution time leads to a more pronounced elliptical shape in the bent sample. For instance, when subjected to heat treatment at 530 °C and 545 °C for 60 min, the samples exhibited respective increases in ellipticity of 5.30 % and 4.34 % compared to those treated for just 30 min. Additionally, higher internal pressure led to a reduction in the degree of elliptical deformation, notably a decrease of 9.85 % observed at a pressure of 20 bar. Moreover, the hardness of samples subjected to the T3 cycle exhibited an upward trend with increasing both temperature and duration of heat treatment. To elaborate, the hardness measurements were conducted at three distinct temperatures (530 °C, 545 °C, and 560 °C) and four different durations (30, 45, 60, and 75 min). The sample subjected to a 75-minute heat treatment at 560 °C exhibited the highest recorded hardness value, measuring at 62.55 HV. In summary, the results indicate that aging heat treatment can enhance the formability of 6063 aluminum tubes during the RDB process. Furthermore, it is noteworthy that temperature and internal pressure serve as crucial parameters to control in order to mitigate elliptical deformation and enhance hardness.