Novel insight into precipitation behavior of gamma ' phase particles in Cu-15Ni-xAl alloys through Calphad method
Novel insight into precipitation behavior of gamma ' phase particles in Cu-15Ni-xAl alloys through Calphad method
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DOI：
10.1016/j.intermet.2020.106749
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发表时间：
2020
期刊：
影响因子：
4.4
通讯作者：
Li T. J.
中科院分区：
文献类型：
--
作者：
Dong B. W.;Jie J. C.;Wang S. H.;Dong Z. Z.;Wang T. M.;Li T. J.
Cu-15 Ni-xAl合金中γ '相（AlNi 3）颗粒的沉淀行为（重量%，x = 0，1，2，3，4）在不同温度下的时效。在一定时效温度下，当Al含量从1wt%增加到4wt%时，γ '相的尺寸从几微米变成几十纳米。结果表明，Al含量的增加会增加单相固溶体（FCC）的不稳定性，表现为G（过剩）（FCC）值的增加，并导致析出临界温度的升高。随着Al含量的增加，固溶时效温度下的过饱和度增加，γ '形核驱动力也随之增加。同时，Cu-15 Ni-4Al合金的析出强化随时效温度从700 ℃降低到400 ℃呈现先增大后减小的趋势，这是由于随着时效温度的降低，形核驱动力的增大与元素自扩散系数的降低相互竞争的结果。γ '相的连续析出和不连续析出行为随着时效温度的降低而分别受到促进和抑制，这是由于较高的形核驱动力所致。然而，当时效温度降低到400 ℃时，由于自扩散系数太低，连续和不连续沉淀都将被抑制。
gamma' phase (AlNi3) particles' precipitation behavior in the Cu-15Ni-xAl alloys (wt.%, x = 0, 1, 2, 3 and 4) ageing at different temperature was systematically discussed with the help of Calphad method. With fixed ageing temperature, when Al content increases from 1 wt% to 4 wt%, the gamma' phase particles transform from a few microns to dozens of nanometers in size. The increasing Al content was proven to raise the instability of single phase solid solution (FCC), which can be expressed by the increasing value of G(excess)(FCC) and will result in the increasing critical temperature for precipitation. Supersaturation at fixed ageing temperature is thus raised with increasing Al content, so does the nucleation driving force of gamma' phase. Simultaneously, the precipitation strengthening in Cu-15Ni-4Al firstly increases and then decrease with ageing temperature decreasing from 700 degrees C to 400 degrees C, which is due to the competition between increasing nucleation driving force and decreasing self-diffusion coefficient of element with decreasing temperature. The continuous and discontinuous precipitation behaviors of gamma' phase were also discussed, which will be respectively promoted and suppressed with decreasing ageing temperature due to the relatively high nucleation driving force. However, both continuous and discontinuous precipitation will be suppressed when the ageing temperature decreases to 400 degrees C due to the too low self-diffusion coefficient.