T6 heat treatment[solution 500 ℃×2 h+（260～360） ℃×（1～8） h] experiments were conducted to investigate the effect of ageing temperature and time on the thermal conductivity of Al-11 Si cast alloy. The results reveal that the thermal conductivity of as-cast and heat-treated Al-11 Si alloy reach 138.5 W/（m·K） and 156.6 W/（m·K）

respectively

which is increased by 14% after T6 treatment. Compared to that treated at aging temperature of 260 ℃

the electrical conductivity of the alloy treated at aging temperature of 320 ℃ can reach a peak value of 29.05 MS/m within 2 h

of which the enhancement is slight when temperature is increased up to 360 ℃. After T6 heat treatment

α-Al dendrite grows and becomes more rounded

and the eutectic Si becomes spheroidal and more uniformly distributed

where the tensile strength is decreased

and the elongation is increased significantly. The precipitation behavior of the Si phase in α-Al leads to significant fluctuations of the lattice constant of the matrix.