Effects of Al Content on Microstructure and Properties of As-cast Ni-20Cr-xAl-1Si Alloys
Ni-20Cr and modified Ni-20Cr-xAl-1Si(x=3,4,5,6,7,mass fraction,％)alloys were prepared by vacuum arc melting,and effects of Al content on resistivity,phase,microstructure and mechanical properties of NiCrAlSi alloy were investigated by XRD,SEM,EPMA,tensile and hardness tests.The results indicate that Ni-20Cr is composed of γ single phase,and Ni-20Cr-xAl-1Si is composed of γ matrix phase and γ'-Ni3Al precipitation phase.With the increase of Al content,the content of γ'-Ni3Al phase is firstly increased and then decreased,which plays an important role in precipitation strengthening and resistivity enhancement,and the solid solution strengthening of Al in γ/γ'phase is gradually increased,leading to the first increase and then reduction of resistivity,gradually increase in the strength and hardness,and gradually decrease in the plasticity and toughness.The resistivity of Ni-20Cr-5Al-1Si alloy reaches 1.523 μΩ·m,which is increased by 43.81％compared with Ni-20Cr.The yield strength,tensile strength and hardness of the alloy are increased to 664.9 MPa,864.6 MPa and 340.8 HV0.2,respectively,while the elongation is decreased to 31.83％.
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