THE EFFECT OF TEMPERATURE AND FE-AL RATIO ON THE FLOW AND FRACTURE OF FEAL

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 (less than or equal to 45 at.% Al), the yield stress exhibited a valley at similar to 500 K and a peak at similar to 675 K before declining rapidly at higher temperatures. The stoichiometric alloy 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 similar 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 greater than or equal to 600 K the fracture mode changed to ductile rupture.