Hydrogen induced fracture in a RSP AlLi alloy

Abstract

Rapid solidification processing (RSP) is an important trend in manufacturing Al-Li alloys, which has many advantages over the ingot metallurgy (IM) method. But, the RSP introduces an important problem with aluminum alloys, namely that of oxide contamination. The extremely large surface areas associated with rapidly quenched particulates, coupled with the reactivity of aluminium and lithium, make it impossible to suppress oxidation of rapidly solidified particulates completely. Therefore, an oxide film is always formed on the powder surface of Al-Li alloys. The oxide film usually contains significant amounts of physically adsorbed water, oxygen and hydrogen. Although a vacuum hot degassing has been carried out before the powders of Al-Li alloys are consolidated, the hydrogen levels in RSP Al-Li alloys are usually high. The embrittlement of aluminum alloys by cathodically charged hydrogen has been extensively investigated, and has been observed to depend on temperature, strain rate and microstructure. It is reported that slip character controls the extent of dislocation transport of hydrogen and thereby may control and dominate the distribution of hydrogen in material and the degree of hydrogen embrittlement. There also have been many studies on the hydrogen embrittlement in IM Al-Li alloys. Here, the influence of hydrogen on the fracturemore » behavior of RSP Al-Li alloys is studied.« less