High damping Al-Zn alloys were developed by spray deposition process. For the optimization of the spray deposition process, an axisymmetric 2 dimensional numerical simulation program was developed. And the damping capacity and mechanical properties of various Al-Zn alloys and Al-Zn-X alloys produced by spray deposition process were measured.
Spray deposition process was modeled by 3 steps. In the first step, the size distribution of the sprayed droplets was predicted by Lubanska relation. In the second step, the variation of the velocity and temperature of droplets were calculated. And the average enthalpy of the droplets was calculated as a function of spray distance. In the third step, the shape and temperature variation of the deposit were calculated. The temperature variation of the deposit was calculated by finite difference method in axisymmetric 2- dimensional coordinate. Solidification process was calculated by enthalpy method and Scheil model was used for the solidification model. The shape and temperature variation of deposit was predicted and the effect of various parameters were also compared. A 1-dimensional simulator was used for estimating the effect of various spray parameters effectively.
The damping capacity and mechanical properties of ingot cast and spray deposited specimens were compared. The materials were binary Al-40, 60, 70 and 78%Zn and Al-78%Zn-0.5%X and 1%X alloys. The third element X were Cu, Mg, Mn and Si. The specimens were prepared by three(A, B and C) different methods. A-specimens were just hot-rolled from as cast or as sprayed state. B-specimens were hot rolled and then T6-treated. C-specimens were T6-treated and then hot rolled. The damping capacity and the strength of the sprayed specimens were higher in binary alloys at the same composition. In the comparison of A and B specimens, B-specimens had higher damping capacity only in Al-78%Zn alloys. As the strength of the binary alloys were very low, third elements were added to improve mechanical properties. Cu or Mg addition increased strength and hardness but decreased damping capacity. Al-Zn-Mg specimens were too brittle and sprayed ones were broken even during hot-rolling. Cast Al-Zn-Mn alloys showed very large intermetallic compound and the damping capacity did not change much but the hardness and the strength decreased. Sprayed Al-Zn-Mn alloys showed smaller intermetallic particles but the strength decreased too. In C-specimens, mechanical working changed the lamella structure of eutectoid transformation into equiaxed fine-grained structure and the damping capacity of Al-70 and 78%Zn were increased.
