Based on the mechanical parts assembly of the twin bar tester of hot tearing linear contraction for alloy

a new way to testing hot tearing behavior of Mg alloy was developed. In the system

resin precoated sand was used as molding material to solve the combustion of Mg alloy during pouring process. The signal data of temperature

stress and shrinkage were recorded and further treated with curves drawn by computer through A/D conversion. Results indicated that AZ91 alloy would precipitate eutectic phase not coinciding with equilibrium phase diagram under the conventional solidification condition. The temperature most susceptible to be hot torn was located near the practical solidified end temperature（420 ℃） for AZ91 alloy.