MICROSTRUCTURE AND DUCTILITY OF RE DOPED RAPIDLY SOLIDIFIED NiAl

The paper investigated the effects of RE on the microstructure and ductility of melt-spun Al-63.3at.%Ni and Al-66.4at%Ni.For Al-63.3at.%Ni without RE the microstructure is a mixture of equiaxed martensitic grains and B2 NiAl grains,but after addition of 0.2wt% RE a complete supersaturated B2 NiAl results,and its elongation is enhanced from 0.9%(without RE) to 1.4%(with 0.2wt%RE).For Al-66.4at.%Ni without RE the microstructure is coarse equiaxed martensitic grains with Ni3Al precipitated at the GBs.But complete martensitic grains and supersaturated single phase,B2 NiAl,would result with addition of 0.05wt%RE and 0.2-0.8wt%RE respectively.The elongation of Al-66.4at.%Ni without RE is only 0.8%.With the addition of 0.05, 0.2 and 0.8wt%RE.the elongation can reach 2.6,3.0 and 3.2% respectively.The addition of RE can change the fracture mode from intergranular fracture(without RE) to a mixture of intergranular and transgranular fracture or entirely transgranular fracture.The mechanisms of microstructure formation and ductility enhancement are analyzed.