Effects of B and Al on tensile strengths and electronic structure of CuZr: A first-principles study

We investigate effects of B or Al impurities on structure and tensile strengths of CuZr by using first-principles density functional calculations. The calculations indicate that B or Al atoms doped on Zr atoms are energies favorable structure. We present stress-strain relationships for Cu-Zr-X (X = B, Al) systems along chosen directions. Both B and lower concentrations of Al decrease the tensile strengths, although there exists stronger covalent bonds between X and nearest neighbor Cu/Zr of Cu-Zr-X than that of CuZr, and plasticity in these systems can be triggered by electronic instabilities under tension. CuZr0.5Al0.5 possesses larger tensile strengths than CuZr, and we analyze mechanism of different tensile strengths for different concentrations of impurities by Mulliken overlap populations. All calculations show that the effects of B or Al impurities on tensile strengths of CuZr are quite composition-dependent.