A kind of massive microstructure αm along the primary α phase(αP) has been characterized in the microstructure quenched from the α+β phase field. The obvious interface between αm and αP can be realized under the optical observation, and the concentrations of Al, Sn, Zr elements in αm are in between the αP and β matrix, but the orientation of the αm keeps consistent with the αP as evidenced by EBSD analysis. The appearence of the αm is considered as the result of limited diffusion controlled transformation from the β phase during the cooling, becasue the αm initiates from the α/β interface and keeps the consistent orientation with αP, and the growth is limited around the α/β interface. As the diffusion is limited by decreasing the solution periods from 30min to 5min, and the dissolving of αP is accelerated by increasing the solution temperature from 1040℃ to 1060℃, the volume fraction of αm increases from 5.2% to 30.7% significantly