The effect of temperature and Fe: Al ratio on the flow and fracture of FeAl

Abstract

Mechanical testing of large-grained binary FeAl alloys as a function of temperature showed that the yield stress decreased rapidly from 77 to 300 K, followed by a slower decrease up to 500 K. For iron-rich alloys (⩽45at.%Al), the yield stress exhibited a valley at ~500K and a peak at ~675K before declining rapidly at higher temperatures. The stoichiometric alloys showed the highest yield stress at all temperatures. The ductility of the off-stoichiometric alloys in vacuum increased with increasing temperature until at 900 K elongations up to ~150% were obtained; the reduction in area showed a sharp transition from <10% below 500 K to > 80% above 600 K. All off-stoichiometric alloys displayed a mixture of intergranular fracture plus transgranular cleavage below 600 K; the amount of cleavage increased with both decreasing iron concentration and increasing temperature. At temperature ⩾600K the fracture mode changed to ductile rupture.