铸态(TiB+TiC)/Ti1100复合材料高温拉伸性能及蠕变行为

High temperature tensile properties and creep behavior of as-cast(TiB+TiC)/Ti1100 composite

通过XRD、SEM、TEM等表征手段研究(TiB+TiC)/Ti1100复合材料的铸态显微组织、高温拉伸性能和高温蠕变行为。结果表明:(TiB+TiC)/Ti1100复合材料具有典型的网篮组织,通过B_(4)C、C和Ti的反应原位生成了晶须状的Ti B和等轴状的TiC。随着温度的升高,(TiB+TiC)/Ti1100复合材料的极限抗拉强度从766 MPa降低至511 MPa。在实验范围内,(TiB+TiC)/Ti1100复合材料的稳态蠕变速率随温度和应力的升高而降低。根据对相关数据的计算,(TiB+TiC)/Ti1100复合材料的应力指数和激活能分别为3.75和269.5 kJ/mol。结合蠕变后的变形区域组织,可以确定该材料的蠕变过程主要受位错滑移控制。α/β界面是位错滑移的主要障碍,同时TiB、TiC和硅化物也阻碍着位错的运动。β-Ti的大量溶解导致硅化物的形成,并降低了α/β界面对位错的阻碍效果。增强相特别是TiB可以通过承载作用,降低基体中的应力集中从而抑制β-Ti的溶解。

The as-cast microstructure,high temperature tensile properties and creep behaviors of(TiB+TiC)/Ti1100 composite were characterized in detail by XRD,SEM and TEM.The results show that the composite possesses a typical basket-weave structure.TiB and TiC are formed in situ through the reaction of B_(4)C,C and Ti.With the increase of temperature,the ultimate tensile strength decreases from 766 MPa to 511 MPa.In the test range,the steady creep rates of(TiB+TiC)/Ti1100 composite decrease with the increase of temperature and stress.According to the calculation of relevant data,the stress exponent and activation energy of the composite are 3.75and 269.5 kJ/mol,respectively.Combined with the microstructure after creep deformation,it can be determined that the creep process is mainly controlled by dislocation slip.Theα/βinterfaces are the main obstacle of dislocation slip,while TiB,TiC and silicides also hinder the movement of dislocations.A large degree ofβ-Ti dissolution leads to the formation of fine silicide and reduces the blocking effect ofα/βinterface on dislocation.The reinforcements,especially TiB,can improve the stress concentration in matrix through the bearing effect and thus inhibit theβ-Ti dissolution.