Effect Of Alloying Elements On The Organization And Properties Of Nickel-aluminum Bronze Alloys In The As-cast State

Nickel aluminium bronze(NAB)alloy and BFe 10-1.6-1(B10)alloy electric coupling match well,with high strength and excellent resistance to seawater corrosion,welding performance,inhibition of marine microorganisms and other characteristics,widely used in copper-nickel alloy seawater pipeline pump valve and other marine engineering equipment manufacturing.The main alloying elements in nickel-aluminium bronze alloys include Al,Ni,Fe,Mn,etc.The type and content of the elements directly determine the organisation and performance of the alloy.The composition of industrial nickel-aluminium bronze alloys has a wide nominal range.In order to further modulate the overall performance of the alloy to suit complex application scenarios,the mechanism of action of the alloying elements needs to be studied in more detail.In this thesis,based on the composition of ZCuAl9-4-4-2 alloy,nine nickel-aluminium bronze alloys were prepared by regulating the content of four alloying elements,including Al,Ni,Fe and Mn.The influence laws of alloy composition on microstructure,mechanical properties and corrosion resistance were investigated using metallographic microscopy,scanning microscopy and electrochemical workstations,providing experimental support for the fine-tuning of nickel-aluminium bronze alloy composition and helping to further explore the performance potential of nickel-aluminium bronze in complex application environments.In the Ni-Al bronze alloy,as the Al content increases from 8 wt.%to 10 wt.%,the content of the strong ?? and ?? gradually increases,while the content of the plastic,matrix a phase gradually decreases.This leads to a decrease in elongation and an increase in strength and hardness of the alloy.Furthermore,the large amount of ?+?? eutectic organisation caused a decrease in the corrosion resistance of the alloy.After 30 days of immersion,the corrosion rate of the alloy increased from 0.0127 mm/a to 0.0164 mm/a.As the Ni content increases from 3 wt.%to 5 wt.%,the matrix a and ?' phase content gradually decreases and the intermetallic compound ? phase content increases,with more Ni elements solidly dissolved in the a phase.The strength and hardness of the alloy increases and the elongation decreases through second phase strengthening and solid solution strengthening.the increase in Ni content reduces the content of the ?' phase,which has poor corrosion resistance,and increases the electrode potential of the alloy,reducing the tendency for galvanic corrosion between the Ni-Al bronze alloy and the B10 alloy.As the elemental Fe content increases from 2 wt.%to 4 wt.%,the ?? phase content gradually increases and the strength and hardness of the alloy rises.elemental Fe inhibits charge transfer on the surface of the alloy,thus increasing the polarisation resistance of the alloy,promoting the generation of nickel-iron oxides,reducing the corrosion depth of the alloy,making the alloy film layer more dense and improving corrosion resistance.As the Mn content increases from 0 to 4 wt.%,the microstructure of the alloy is gradually refined,with the refinement of the matrix a phase being more significant and the stability of the ? phase being improved.the change in Mn content has almost no effect on the static corrosion resistance of the alloy,but the 2 wt.%Mn content increases the polarisation resistance of the alloy and reduces the galvanic coupling corrosion tendency of the Ni-Al bronze alloy with the B10 alloy.