Effect Of Element Y On Microstructure And Properties Of FeCrAl Alloy

FeCrAl alloy has good oxidation resistance and low thermal neutron absorption cross section,and the alumina formed on the surface of FeCrAl alloy can effective hinder hydrogen diffusion and is an ideal material for nuclear fuel cladding.The FeCrAl alloys containing 0,0.044%,0.24%and 0.66%of Y elements were prepared by vacuum induction melting,the microstructure observaed,phase composition analyzed,thermal simulation tested,impact property test and tensile property test were carried out.The effect of Y on the microstructure and mechanical properties of FeCrAl alloys was investigated.By studied the as-cast microstructure of FeCrAl alloys and the deformation behavior under hot deformation conditions,the effect of heat treatment on microstructure and tensile properties of FeCrAl alloys were investigated.Getting the main conclusions:FeCrAl alloy is a body centered cubic?BCC?ferrite,When the Y element increase from0 to 0.24%in the as-cast state,the grain size be gradually refined,however,when the content of Y increases to 0.66%,the effect of grain refinement not obviously,and the forging ability of alloy be reduced.The solid solubility of Y element in FeCrAl alloy is very low,When the Y element content is 0.044%,there is no Fe-Y phase precipitated,but when the Y content exceeds its solid solubility in?-Fe,the extra Y will form the Fe-Y phase with Fe?Cr?Al atoms.The Fe-Y phase molecular formula is?-Fe₁₇Y₂,which is distributed in the matrix with spheres and networks,and the high temperature treatment has no effect on it.The dynamic recrystallization were not easy to occur of the cast FeCrAl alloys.the incomplete dynamic recrystallization takes place at the deformation of 40%and 1100?.The dynamic recrystallization was easily occurs when the greater deformation and the higher temperature.The as-cast FeCrAl alloy has good plasticity,the Fe-Y phase in high Y element alloy significantly increases the strength and the deformation resistance of FeCrAl alloy,but it reduces the plasticity of FeCr Al alloy.The annealing heat treatment temperature is from 650?to 850?for an hour followed by water quenching,and the tissue was gradually transformed from the deformation tissue into the equiaxial grain structure,the microstructure had no obvious change when the annealing at temperature is 650?.When the annealing temperature at 700?to 750?,the mixed tissue of local equiaxial crystal tissue and rheological strip is present.FeCrAl alloys dynamic recrystallization completely when the annealing temperature rise to 800?and 850?,the grain was growth when the annealing temperature is 850?.During annealing process there is M₂₃C₆ phase appear.The Fe-Y phase in FeCr Al alloy containing high Y element can effectively prevent grain growth.The fracture mode of the impact pattern of FeCrAl alloy was the transgranular fracture along cleavage surface,and the alloy impact energy increased first and then decreased with the increase in the content of Y element.The tensile fracture of FeCr Al alloy is the fracture of ductile shear slip type and transgranular fracture,the yield strength and tensile strength decrease with the increase of temperature.The plasticity at room temperature is better than at400?,and the element Y has no obvious effect on tensile strength at room temperature and 400?.