The effects of temperature and time during solution treatment and aging treatment on the microstructure and mechanical properties of AlSi12 CuMgNi alloy were investigated. The results indicate that when solution temperature is in the range of 490～560 ℃

the strength and hardness of the alloy are increased firstly and then decreased with holding time and the temperature variation. The burnt phenomenon appears at 550 ℃

and the hardness reaches peak value with the lower residual stress after 535 ℃×2 h. After solution treatment at 535 ℃ for 2 h and aging treatment at 180～260 ℃ for 6～9 h

strengthening phase is precipitated with time and temperature variation

where the strength and hardness are increased firstly and then decreased. When the temperature reaches 240 ℃

the over-aging is obvious

and the strength and hardness are significantly decreased. After solution treatment at 535 ℃ for 2 h and aging treatment at 200 ℃ for 8 h

the hardness reaches 150 HB

and tensile strength is more than 320 MPa

where the residual stress is significantly lower than that before solution.