Effects of impurities and stacking fault energy on shock-induced phase changes in copper alloys*

Recent publications suggest a relationship between stacking fault (SF) generation and the face-centered cubic (FCC) to body-centered cubic (BCC) phase transformation in shock-compressed noble metals. Metal alloying is well known to affect many material properties including stacking fault energy (SFE) and phase stability regions. To examine the effect of impurities on stacking fault generation and high-pressure phase boundaries, we performed laser-shock in-situ X-ray diffraction (XRD) experiments on three copper alloys with SFEs between 10 and 90 mJ/m². For the different Cu alloys (≥70% Cu), we found FCC to BCC transition stresses between ~130 and ~280 GPa, highlighting the large effect impurities can have on transition stress. Due to the observed linear relationship between SFE and FCC to BCC transition stress, for small impurity contents, we expect minimal phase boundary changes.