Development of Directionally Solidified TiAl/Ti3Al Alloys

定向凝固TiAl/Ti3Al合金的研制

基本信息

批准号：
06555203
负责人：
YAMAGUCHI Masaharu
金额：
$ 11.07万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Directionally solidified ingots containing only one lamellar orientation for the complete ingot can be produced. Unfortunately, the lamellar microstructure in these ingots was perpendicular to the growth direction. However, since only one orientation was observed, microstructural control may be achievable by using a seed crystal during directional solidification. There are two requirements that must be met if the orientation of the lamellar microstructure is to be controlled by using a seed crystal. The first is that the alpha phase must nucleate first from the liquid. The basic idea is to control the orientation of the alpha phase upon nucleation. Since the lamellar microstructure forms with the (111) gamma// (0001) alpha orientation relationship, once the orientation of the alpha phase is determined, the orientation of the lamellar microstructure is also determined. Secondly, upon heating or cooling, either the alpha phase or the alpha-2 phase must be thermodynamically stable. That is, upon heating or cooling, the alloy must not pass through the gamma single-phase region since recrystallization may occur. These two requirements are met in the TiAl-Si system. Within the composition range of 40-50 at%Al, the addition of Si to TiAl shifts the primary alpha region towards much lower Al content. At a composition of Ti-43Al-35Si, either alpha or alpha-2 is stable from the melting temperature to room temperature and the orientation of the lamellar microstructure can be controlled using a seed material. The room temperature mechanical properties were determined by tensile tests and by three point bend tests. From bend specimens oriented with the notch parallel to the lamellar microstructure, the Ti-43Al-3Si alloy was found to have a greater fracture toughness than a TiAl-PST crystal of the same orientation.

可以产生仅包含一个层状方向的定向固化锭。不幸的是，这些铸锭中的层状微观结构垂直于生长方向。但是，由于仅观察到一个方向，因此可以在定向固化过程中使用种子晶体来实现微结构控制。如果要通过使用种子晶体来控制层状微结构的方向，则必须满足两种要求。首先是α相必须首先从液体中核定。基本思想是控制成核时α相的方向。由于层状微结构形成（111）γ//（0001）α取向关系，一旦确定了α相的方向，因此还确定了层状微结构的方向。其次，加热或冷却后，α相或α-2相必须在热力学上稳定。也就是说，在加热或冷却后，由于可能发生重结晶，因此不得穿过伽马单相区域。这两个要求在TIAL-SI系统中满足。在40-50 at％Al的组成范围内，将Si添加到TIAL中会将主要α区域转移到较低的含量。在TI-43AL-35SI组成下，α或alpha-2从熔化温度到室温是稳定的，并且可以使用种子材料来控制层状微结构的方向。通过拉伸测试和三个弯曲测试确定室温机械性能。从与层状微结构平行的凹口样品相比，发现TI-43AL-3SI合金比相同方向的TIAL-PST晶体具有更大的断裂韧性。