Abstract

This work is devoted to the finite-element modeling of the deformation mode of a small-diameter rod billet during pressure hot treatment in the combination of radial shear rolling (RSR) and rotary forging (RF). Modeling is performed using a rheological model of the Ti–6Al–4V titanium alloy using the QForm VX program. The combination of RSR for one passage of a billet 15 mm in diameter to a rod 12 mm in diameter and subsequent RF in 1, 2, and 3 passages with the formation of rods 11, 10, and 8 mm in diameter is modeled. The operation-by-operation accumulation of the plastic deformation in nonuniformity conditions of its distribution is taken into account. Intermediate and final plastic deformation fields, deformation rates, and average stresses are found. It is shown that the distribution of the plastic deformation after RSR has the pronounced gradient character with a minimal value (3 and larger) at the cross-section periphery and a minimal value (about 1) in the center. Due to this, RF, even with small reductions, leads to a substantial increase in uniformity of the deformation mode when compared with the billet after the same diameter after radial shear rolling only. In addition, residual tensile stresses decrease due to compressing stresses during RF. The direct experimental approval of the combined deformation method is performed for the promising Ti–Zr–Nb shape memory alloy of medical prescription when fabricating rods 7–8 mm in diameter under pilot production conditions. The results of modeling are qualitatively confirmed by the metallographic analysis. The prospects of a combination of RSR and RF for the development of industrial fabrication technologies of small-diameter rods with a high uniformity of finely dispersed structure are shown.

中文翻译：

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径向剪切滚轧与旋转锻造结合对钛合金小直径棒坯变形方式的影响

摘要

这项工作致力于径向剪切轧制（RSR）和旋转锻造（RF）组合的压力热处理中小直径棒坯的变形模式的有限元建模。使用QForm VX程序，使用Ti-6Al-4V钛合金的流变模型进行建模。对将直径为15毫米的钢坯一次通过到直径为12毫米的棒材的RSR与随后的1、2和3道次RF形成的直径11、10和8毫米的棒材的组合进行了建模。考虑到塑性变形在其分布的不均匀条件下的逐次累积操作。找到中间和最终塑性变形场，变形率和平均应力。结果表明，RSR后的塑性变形分布具有明显的梯度特征，在横截面外围具有最小值（3和更大），在中心具有最小值（大约1）。因此，与仅径向剪切轧制后的相同直径的钢坯相比，RF即使减小的幅度也很小，但导致变形模式的均匀性大大提高。另外，残余拉伸应力由于RF期间的压缩应力而降低。当在中试生产条件下制造直径7-8 mm的棒时，对有希望的医学处方Ti-Zr-Nb形状记忆合金进行了组合变形方法的直接实验批准。通过金相分析定性地证实了建模结果。