Abstract: An equipment was developed to study the solidification characteristics during free and blocked contraction. The solidification contraction behaviors of 5083， 6061 and 7075 aluminum alloys were investigated to predict the hot cracking tendency， and the stress accumulating coefficient (k) was introduced to evaluate the hot cracking tendency. The results indicated that the equipment can record the subtle changes of temperature， thermal shrinkage displacement and shrinkage stress during solidification. Combined with the calculation of thermal software JMatPro， four solidification stages are proposed. The sequence of hot cracking tendency of three investigated alloys is k(5083)＞k(7075)＞k(6061)， which coincides with the result during reality casting and the result of CSC. All the results indicate that the developed equipment and the data analysis method are available， and k can be used to predict accurately the hot cracking tendency of aluminum alloys.

Key words: solidification contraction, hot cracking tendency, stress accumulating coefficient, soliclification characteristic, aluminum alloys