Effect of Aluminum Content on Microstructure and Properties of Powder Metallurgy CoCrFeMnNi High-entropy Alloy
CoCrFeNiMn high-entropy alloy(HEA)generally exhibits outstanding ductility and fracture toughness properties,however its low strength and hardness limit its application potential in the field of structural materials.There are few reports on the effect of Al content on microstructure and properties of CoCrFeMnNi HEA fabricated by powder metallurgy at present.CoCrFeMnNi HEAs with different Al content were prepared by hot-pressing sintering method using gas-atomized HEA powder and Al powder as raw materials.The effect of Al content on microstructure and properties of HEAs was investigated by means of X-ray diffraction(XRD),scanning electron microscopy(SEM)/energy dispersive spectroscopy(EDS),nanoindentation experiment,vickers hardness,compression at room temperature and polarization curves.The results show that with the increase of Al content from 0 to 5 wt.％,the relative density and the volume fraction of reticular Cr-rich BCC phase precipitated in the FCC matrix of as-prepared HEAs increase.When the Al content increases to 5 wt.％,the nano-indentation hardness and elastic modulus of the FCC phase in fabricated HEA increase slightly and the mentioned performance of BCC phase is significantly higher than that of FCC phase,the vickers hardness increases from 248.4 to 508.3 HV and the compression strength at room temperature is also greatly improved mainly due to the precipitation strengthening effect;At the same time,the minimum corrosion current density is obtained,confirming the improved corrosion resistance.However,the addition of excessive Al leads to the segregation of Al element,and a sharp increase in the volume fraction of BCC structure and microstructural heterogeneity of as-fabricated HEA,which deteriorates the hardness,elastic modulus and corrosion resistance.
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