Recently, CO_2 emission regulation in automobile industry has been started and improvement of fuel consumption is required from the view points of global warming and energy problems. Weight reduction is one of the ways to solve these requirements. Aluminum alloy with superior strength and high specific gravity will be a candidate material for reducing the weight of automobile structural components. As automobile components, high fatigue strength and toughness as well as tensile strength are required. However, improvement of strength tends to decrease toughness. In the present study, effects of microstructure on fatigue strength and toughness of 6000 aluminum alloys have been reported.
