Embrittlement of zinc by liquid metals

Abstract

The liquid metal embrittlement (LME) of pure polycrystalline zinc in tension has been studied at different temperatures and strain rates. LME was observed with gallium, mercury, indium, and tin, as expected, but also with bismuth and cadmium, contrary to previous reports. At moderate strain rates, e.g. 1.4×10⁻³ s^−l, the embrittlement with gallium, mercury, indium, and tin generally occurred within a limited temperature range whose lower limit was independent of strain rate and appeared to be the embrittler melting point in the case of gallium and mercury; with indium and tin, however, it coincided with the eutectic temperature of the zinc-embrittler system. The upper limit of the range was dependent on strain rate and increased as the strain rate increased, although in some cases embrittlement persisted to at least 350°C without ductile behaviour being re-established. At low strain rates it was possible to restrict the embrittlement range to an interval of only a few degrees. This observation has important implications for the technological use of stressed solid metals in contact with liquid metals. The results have been analysed in terms of the reduction in surface energy hypothesis and an encouraging correspondence exists between the severity of embrittlement, as measured by mechanical tests, and both experimental and theoretical estimates of solidjliquid interfacial energies. This correspondence offers tentative prospects for the prediction of LME effects.