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研究了多功能亚稳β型Ti2448(Ti 24Nb-4zr-8Sn,质量分数,%)合金在β单相区的高温变形行为.结果表明.在低应变速率(≤0.1 s~(-1)和高应变速率(≥1 s~(-1))条件下,真应力和应变速率的双对数关系可以通过2个线性关系分别表征,平均应变速率敏感值(mavg)分别为0.265和0.032,这不同于常规β钛合金随着应变速率的增大而逐渐降低的应变硬化规律,即Sigmoidal曲线特征.微观组织演化和动力学分析显示,这种特殊的双线性关系与高应变速率导致的局域化非均匀塑性变形行为和动态再结晶(DRX)相关联.尽管动态回复(DRV)是该合金高温塑性变形的主要组织演变机制,高应变速率使得组织演变从DRV向DRX转变,并在交错的变形带内形成小于3μm的细晶组织.因此,高应变速率条件下的DRX是实现Ti2448合金高温变形过程中细化组织的主要机制.
The deformation behavior of multi-functional metastable beta Ti-Ti alloy Ti2448 (Ti 24Nb-4zr-8Sn,%) alloy in the single-phase β region was studied.The results show that when the low strain rate (≤0.1 s -1 Under the conditions of high strain rate (≥1 s ~ (-1)), the logarithmic relationship between true stress and strain rate can be characterized by two linear relationships respectively. The average strain rate sensitivity values (mavg) are 0.265 and 0.032, respectively Which is different from that of the conventional β-titanium alloy which gradually decreases with the increase of strain rate, that is the Sigmoidal curve.Microstructure evolution and dynamic analysis show that this particular bilinear relationship is related to the high strain rate Domain-induced non-uniform plastic deformation behavior correlates with dynamic recrystallization (DRX). Although dynamic recovery (DRV) is the dominant tissue evolution mechanism for high-temperature plastic deformation of this alloy, high strain rates cause the transformation of the tissue from DRV to DRX, Of the deformation zone to form fine grain structure less than 3μm.Therefore, the DRX under high strain rate is the main mechanism to refine the structure during the high temperature deformation of Ti2448 alloy.