TC18钛合金棒材锻造织构的模拟

Simulation of texture formation in hot forged TC18 titanium bars

摘要:

通过三向锻造方式模拟TC18钛合金棒材锻造过程织构形成的规律和不均匀性。首先用有限元法模拟了三向锻造时样品不同区域的温度、等效应力和等效应变的不均匀性。然后模拟了对应b相(BCC结构)不同位置,不同锻造阶段、不同初始织构的影响。结果表明,在三向锻造的顺序锻造过程中,心部织构变化程度远大于边部。三向锻造后心部出现立方压缩织构和黄铜型拉伸织构,边部出现较弱的{100}和{111}压缩织构。初始织构有显著的影响,随机分布的初始织构下,最后一次压缩决定最终织构；偏离随机分布的弱织构时,最终织构也接近随机状态；但不同类型的强初始织构存在时,三向锻造后都难以彻底改变初始织构的影响,最终织构都有初始织构的特征。最后进行了三向压缩时不同形变量的组合对织构的影响模拟,确定出了特殊织构形成的条件。本文还给出横向位置变化和轴向位置变化时织构变化的差异。

Abstract:

Three directional forging textures and their non-uniformity under different conditions were simulated to explain the formation of forging texture in forged TC18 titanium alloy bars. Firstly, finite element method is used to simulate the non-uniform distributions of temperature, effective stress and effective strain in forged bars. Then the textures in b-phase with BCC structure are simulated using visco-plastic self-consistent model(VPSC) under different initial conditions. Results show that during three directional forging the textures in center region changes more apparently than in edge region. The compressive cube texture {100}<001> and brass type texture {110}<112> generally develop in center region, whereas weak compressive {100} and {111} texture are involved. Initial texture plays important role. By random initial texture, the third step compression often determines the final texture. By weak initial texture the final texture is also weak. In contrast, when strong initial texture exists, three directional forging can’t change its influence with characteristic feature of its initial state. Finally the influences of different combinations of strain amounts in three directions are simulated and special condition for large difference in textures is determined. The texture changes along axial and radical directions are also simulated.