Plastic flows and strain-induced alpha to omega phase transformation in zirconium during compression in a diamond anvil cell: Finite element simulations
Plastic flows and strain-induced alpha to omega phase transformation in zirconium during compression in a diamond anvil cell: Finite element simulations
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DOI：
10.1016/j.msea.2016.10.082
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发表时间：
2017-01-05
期刊：
影响因子：
6.4
通讯作者：
Levitas, Valery I.
中科院分区：
文献类型：
--
作者：
Feng, Biao;Levitas, Valery I.
采用有限元方法研究了锆合金在金刚石压砧中压缩时的耦合塑性流动和应变诱导共晶相变。PT被视为应变诱导而非压力诱导，并使用先前开发的应变诱导PT模型。非常不均匀的领域的应力张量，累积塑性应变，和浓度的共相得到不同的施加载荷。当压力超过最小压力p（ε）（d）= 1.7 GPa时，PT开始于样品中心，在此压力下，直接应变诱导PT不能达到高压阶段，随着载荷的增加，PT从中心向周边扩展。即使在7 GPa的最大压力下，PT也不是到处都完成的。随着载荷的增加，由于Ω相的屈服强度大得多，因此在两相区中沿径向方向的压力和压力梯度沿着显著增加。这反过来又促进转化并产生积极的机械化学反馈。获得的结果用于解释已发表的实验数据的压力，应力和应变诱导的α-> ω PT在Zr和钛（Ti）和α-> β和ω-> β PT在Zr压缩和高压扭转。这包括由于应力不均匀性、传输介质的影响、压力滞后和转换的可逆性而将这些转换的报告最小压力校正3-6倍。
Coupled plastic flows and the strain-induced a co phase transformation (PT) in a zirconium sample under compression in a diamond anvil cell are investigated using finite element method (FEM). The PT is treated as strain-induced rather than pressure-induced and the previously developed model for strain-induced PTs is utilized. Very heterogeneous fields of stress tensor, accumulated plastic strain, and concentration of the co phase are obtained for different applied loads. The PT starts at the center of a sample when pressure exceeds the minimum pressurep(epsilon)(d) = 1.7 GPa, below which a direct strain-induced PT to a high pressure phase cannot occur, and it propagates from the center to the periphery with an increasing load. Even at the maximum pressure of 7 GPa, the PT is not completed everywhere. With an increasing load, the pressure and pressure gradient along the radial direction significantly increase in the two-phase region due to the much larger yield strength of the omega phase. This in turn promotes transformation and produces a positive mechanochemical feedback. Obtained results are utilized for the interpretation of published experimental data on pressure-, stress-, and strain-induced alpha ->omega PTs in Zr and Titanium (Ti) and alpha ->beta and omega ->beta PTs in Zr under compression and high pressure torsion. This includes correcting the reported minimum pressures for these transformations by a factor of 3-6 due to the stress heterogeneity, the effect of transmitting media, the pressure hysteresis, and the reversibility of the transformation.