Generally, natural aging at room temperature is very long times process to diffusion precipitate, whereas at high temperatures, where diffusion is rapid. In artificial aging treatment, as the temperature of aging increases, the time taken to reach peak hardness decreases but if the temperature aging is too high , mechanical properties will decrease. So the proper temperature that we use to precipitation aging of 6xxx series alloy is 170°C. Moreover if use too much time, the strength will decrease too. It’s call over aging