A high-frequency induction heating apparatus was used for the heat treatment of a commercial 6061 aluminum alloy bar with the objective of improving the mechanical properties and productivity. Heating states of the 6061 alloy bar were examined in terms of temperature distribution, heating rate, overheating and temperature fluctuation; moreover, the mechanical properties of the alloy after heat treatment were also investigated. The results of this study are as follows. When the 6061 alloy bar was rapidly heated to the heat treatment temperature using the induction heating apparatus, temperature distribution and overheating of the sample were small as well as the temperature fluctuations in the holding process. A rapid heating rate of about 21 C/s heated the sample to the heat treatment temperature of 560 C in 26 s. The sample showed equivalent or superior mechanical properties compared with a sample heated by conventional electric furnace. Temperature and time of the heat treatment process greatly influenced the mechanical properties of the 6061 alloy, while there was no significant difference in mechanical properties of the sample heat-treated at various heating rates.

A commercial 6061 aluminum alloy bar was partially reinforced using a high-frequency induction heating apparatus. One end of the bar was locally heated for solution treatment (local solution treatment). The power supplied to a heating coil was adjusted based on the surface temperature of the bar, which was measured using a radiation thermometer. The temperature profiles and hardness distributions in the longitudinal direction were investigated after the local solution treatment. The results of this study are as follows. The local solution treatment achieved a rapid heating rate of 80 K/s, overheating of about 2 K at the temperature transition stage from the heating to holding process, and a small-scale temperature fluctuation (below «8 K) in the holding process. The reproducibility of the temperature profile during the local solution treatment was also sufficient. An increase in the hardness was achieved from solution treatment at 723 K or more. A holding time of 5 min or more was not very important for increasing in the hardness. The partial reinforcement of a 6016 aluminum alloy bar can be realized by applying an induction heating apparatus.