Huang Xiaoxu

On deformation-induced continuous recrystallization in a superplastic AlLiCuMgZr alloy

Abstract The microstructural changes of a warm rolled AlLi alloy occurring during static annealing and superplastic deformation at 515°C were studied by means of transmission electron microscopy. Deformation induces a continuous recrystallization with a rapid subgrain growth and a rapid increase in boundary misorientations. The higher strain rate results in a faster subgrain growth and a finer recrystallized grain size. The increasing rate of boundary misorientations and the strain at which the average misorientation reaches about 20° increase with increasing strain rate. The increase in boundary misorientations is proportional to the subgrain growth during the whole static annealing process. Deformation results in a more rapid increase in boundary misorientation with subgrain size than static annealing. Dislocation gliding plays an important role before the formation of high angle grain boundaries during superplastic deformation. The absorption of dislocations into subgrain boundaries results in a more rapid increase in boundary misorientation during deformation. Thus, the mechanism of the deformation-induced continuous recrystallization is suggested to be the generation of dislocations in grains and the absorption of gliding dislocations into subgrain boundaries.

New method for determining grain boundary parameters

Abstract With the aid of a TEM double-tilt holder, a new method for determining grain boundary parameters, the misorientation axis, misorientation angle and the boundary normal is developed. Using the new method, three zone-axis directions from each of both grains are aligned to the beam direction and the corresponding tilt angles are obtained from the meter reading of the holder. After inputting these data, the misorientation axis and angle can be calculated precisely and rapidly with the aid of computer software. For determining the boundary normal, using the new method two vectors lying in the plane of boundary are determined by measuring the change of the projections of two vectors from two micrographs of the boundary taken before and after an adjustment of the double-tilt holder. The boundary normal is the cross product of these two vectors. Thus, the new method is considered to be simpler and more convenient when compared to other methods since no Kikuchi pattern needs to be taken.

TEM method for rapid and precise evaluation of continuous recrystallization

Abstract With the aid of a double-tilt holder in a transmission electron microscope, a new method for a rapid and precise determination of the misorientations of a large number of subgrain or grain boundaries is given in this article. By use of the method, the continuous recrystallization can be rapidly and precisely evaluated when compared to the other conventional methods.