1) The document discusses fatigue and residual stresses in aluminum alloys used for engine blocks. It aims to reduce the weight of engine blocks by using aluminum alloys instead of cast iron. [2) Heat treatment solutions like T6 and T7 are explored to address fatigue issues, while solution heat treatment is applied to reduce residual stresses. Experiments involve applying different heat treatments and measuring their effects. [3) Key results found that solution heat treatment at 470C for 5 hours completely relieved residual stresses, and heat treatment improved fatigue life by reducing defects that initiate cracks.