Production of TiAl sheet by cold-rolling

在室温下生长并轧制了具有近化学计量比组成的TiAl多晶孪晶。在没有断裂的情况下可获得的最大总厚度压下量取决于相对于轧制平面和轧制方向的片层取向。当试样在轧制过程中平行于片层边界的剪切变形起作用并导致试样伸长时，这种试样可以被轧制到厚度减少约50%。显微硬度的变化被认为是发生在两个阶段，无论减少量;第一个圣人与位错密度的减少和第二阶段与退火的变形孪晶在轧制过程中引入的TiAl薄板。然而，再结晶模式被发现根据厚度减少量而变化。在轧制到厚度减少小于20%的试样中，硬度完全恢复，保持层状结构。提出了一种机制来解释不寻常的再结晶行为的PST TiAl冷轧到小于20%。在本研究的后期，PST TiAl中发生的环境脆化。然后，进行合金化尝试以减少延展性的环境损失。与二元PST晶体相比，Cr、Mo、V或Mn改性的PST TiAl显示出较小的环境塑性损失。特别地，添加Cr在减少TiAl的环境脆化方面是有效的。最近，我们证实，铬改性的PST TiAl可以冷轧到50 W的厚度比二元PST TiAl更容易减少。

Polysynthetically twinned (PST) crystals of TiAl with a nearly stoichiometric composition have been grown and rolled at room temperature. The maximum total reduction in thickness which is attainable without fracture depends on lamellar orientation with respect to the rolling plane and rolling direction. When specimens are oriented such that shear deformation parallel to the lamellar boundaries is operative during rolling and its operation causes lengthening of specimens, such specimens can be rolled up to about 50 % reduction in thickness.The recovery and recrystallization behavior of cold-rolled PST crystals of TiAl was also investigated. The change in microhardness was found to occur in two stages regardless of the amount of reduction ; the first sage associated with the decrease in dislocation density and the second stage related with the annealing-out of deformation twins introduced in TiAl lamellae during rolling. However, the recrystallization mode was found to vary depending on the amount of reduction in thickness. In specimens rolled to less than 20 % reduction in thickness, th full recovery in hardness occurs preserving the lamellar structure. A mechanism is proposed to interpret the unusual recrystallization behavior of PST TiAl cold-rolled to less than 20 %.At the later stage of this research, environmental embrittlement was found to occur in PST TiAl. Then, alloying attempts were made to reduce the environmental loss in ductility. The Cr, Mo, V or Mn modified PST TiAl was found to show a small environmental loss in ductility as compared with the binary PST crystals. In particular, the addition of Cr is effective in reducing environmental embrittlement of TiAl. Recently, we confirmed that the Cr-modified PST TiAl can be cold-rolled to 50 w reduction in thickness much more easily than the binary PST TiAl.