Effect Of Microalloying And Heat Treatment On Microstructure And Properties Of Aluminum Bronze

Aluminum bronze is an engineering material with good corrosion resistance and mechanical properties.It is widely used in shipbuilding and machinery manufacturing.Aluminum bronze is usually exposed to seawater for a long time during work and carries high loads.Therefore,ensuring the excellent corrosion resistance of aluminum bronze and improving its strength will be the main direction of aluminum bronze research in the future.In this paper,Cr,Zr,Nb,and Co are added to ZCu Al₈Mn₁₃Fe₃Ni₂aluminum bronze in small amounts,and the effects of four microalloying elements on the as-cast microstructure,phase composition,mechanical properties,and corrosion resistance of multiple and complex aluminum bronzes are studied.On this basis,the better microalloying element Cr was selected,and the effects of Cr addition amount and heat treatment on the as-cast microstructure,phase composition,mechanical properties and corrosion resistance of multi-element complex aluminum bronze after Cr microalloying were systematically studied.Research indicates:（1）The addition of 0.3 wt.%Cr to the multi-element complex aluminum bronze promoted the precipitation of the k phase in the alloy structure.The proportion of the k-phase in the alloy increased by about 2 times compared to the non-microalloyed multi-element complex aluminum bronze.The dispersion strengthening effect increases the strength of the alloy;after adding 0.3 wt.%Zr to the multi-element complex aluminum bronze,the mixed area ofβphase andγ₂ phase increases by about1/4,and theα-phase changes from massive to bamboo leaf shape;in multi-element complex aluminum The addition of 0.3 wt.%Nb in bronze can promote the refinement and increase ofαphase,and the refinement of the structure can increase the strength of the alloy.After adding 0.3 wt.%Co to the multiple complex aluminum bronze,the alloy structure is refined and theαis promoted.The increase of phase and k phase makes theαphase in the alloy structure increase slightly,and the k phase increases by about 1.4times.With the refinement of the structure and the dispersion strengthening of the k phase,the strength of the alloy increases.（2）The addition of Cr,Nb,and Co improves the tensile strength of the alloy,and the addition of Zr has no significant effect on the tensile strength of the alloy.After adding 0.3 wt.%Cr,the hardness of the alloy was increased from 196HV to 217HV,the tensile strength was increased from 705MPa to 775MPa,and the elongation after breaking was reduced from 24.8%to 18.2%;after adding 0.3 wt.%Zr,the alloy Its mechanical properties are basically equivalent to the mechanical properties of unmicroalloyed aluminum bronze;after adding 0.3 wt.%Nb,the hardness of the alloy is increased from 196HV to 210HV,the tensile strength is increased from 705MPa to735MPa,and the elongation after fracture is changed from 24.8%decreased to 20.2%;after adding 0.3 wt.%Co,the hardness of the alloy increased from 196HV to 215HV,the tensile strength increased from 705MPa to 764MPa,and the elongation after breaking decreased from 24.8%to 18.8%.（3）The addition of Cr,Zr,Nb,and Co changes the uniform corrosion rate of the alloy.Among them,Cr,Zr,and Co reduce the corrosion resistance of the alloy slightly,and Nb improves the corrosion resistance of the alloy,of which 0.3 Cr-ZT,0.3 Zr-ZT,The uniform corrosion rate of 0.3 Nb-ZT,0.3 Co-ZT and unmicroalloyed aluminum bronze is 0.3 Zr-ZT,0.3 Cr-ZT,0.3 Co-ZT,respectively.0.3 Nb-ZT.but under the test conditions,the uniform corrosion rate of all alloys is lower than the national standard extremely corrosion-resistant material’s ultimate corrosion rate of 0.05mm/a.（4）The tensile strength of the alloy increased with the increasing Cr content,but the rate of increase gradually decreased with increasing Cr content.After comprehensive consideration,the comprehensive properties of the alloy with Cr addition of 0.3 wt.%were the best.（5）When the amount of Cr was increased to 0.5 wt.%,A large number of petal-like Al Cr Fe2 phases precipitated in the alloy.A large amount of petal-like phases precipitated in the alloy after heat treatment with 0.3 wt.%Cr added,and the number and size of petal-like phases increased with the increase of the holding temperature or the holding time,and the petal-like phase and the k-phase lattice The constants are similar and the crystal structure is the same,resulting in the Al Cr Fe₂ phase precipitating in the shape of petals around the k-phase core.（6）Heat treatment makes the tensile strength of aluminum bronze with 0.3 wt.%Cr increased first and then decreased,and it conformed to the general rule of aging.The alloy was kept at 300℃for 2 hours to reach the peak aging,and the tensile strength of the alloy was 828MPa,the hardness was 227HV,and the elongation after breaking was15.1%.Although the 0.3 wt.%Cr microalloyed aluminum bronze had improved the uniform corrosion rate after heattreatment,it still reached the national standard for extremely corrosion-resistant materials.