Identification of constitutive model parameters for nickel aluminum bronze in machining

The material of nickel aluminum bronze (NAB) presents superior properties such as high strength, excellent wear resistance and stress corrosion resistance and is extensively used for marine propellers. In order to establish the constitutive relation of NAB under high strain rate condition, a new methodology was proposed to accurately identify the constitutive parameters of Johnson?Cook model in machining, combining SHPB tests, predictive cutting force model and orthogonal cutting experiment. Firstly, SHPB tests were carried out to obtain the true stress?strain curves at various temperatures and strain rates. Then, an objective function of the predictive and experimental flow stresses was set up, which put the identified parameters of SHPB tests as the initial value, and utilized the PSO algorithm to identify the constitutive parameters of NAB in machining. Finally, the identified parameters were verified to be sufficiently accurate by comparing the values of cutting forces calculated from the predictive model and FEM simulation.

Correlation between microstructure and corrosion and cavitation erosion behaviors of nickel aluminum bronze

The microstructure,corrosion and cavitation erosion(CE)behaviors of the as-cast and four different heat treated nickel aluminum bronzes(NABs)in 3.5 wt.%NaCl solution were investigated.The results show that after annealing,β′transformed into the eutectoid microstructure,and moreκIV precipitated fromα.Less eutectoid microstructure and moreβ′were obtained after normalizing.The quenched NAB mainly consisted ofαandβ′phases,and fine,acicularαandκphases precipitated insideβ′after subsequent aging.The largest proportion of the eutectoid microstructure,which underwent severe selective phase corrosion,was responsible for the lowest corrosion resistance of the annealed NAB.The quenched NAB possessed the most protective film and hence the highest corrosion resistance.The mechanical attack was primarily responsible for the CE damage for the as-cast,annealed and normarlized NABs.The quenched and quenched+aged NABs exhibited superior CE resistance because of the high hardness.The CE−corrosion synergy dominantly caused CE degradation,and it was largely attributed to corrosion-enhanced-CE.

Effect of microstructure on the mechanical and corrosion behaviors of a hot-extruded nickel aluminum bronze

In this paper, the influence of microstructure on the corrosion behavior of a hotextruded nickel aluminum bronze was studied. Three kinds of samples subjected to the hot-extrusion, anneMing and quenching conditions were prepared and immersion tests in 3.5% NaCl solution were carried out. Microstructures and corrosion surface morphologies of the samples were observed by SEM. It was found that the retained β＇ martensite and （α＋kiii） lamella eutectoid in the as hot-extruded material were eliminated after annealing, and corrosion resistance of the alloy was improved. As to the as-quenched material, its corrosion rate was higher than that of the as hotextruded material since the volume fraction of β＇ phase which was anodic to α phase increased after quenching. As regards the mechanical properties, the as-quenched sample possesses the highest hardness and tensile strength among the three kinds of samples, while the as-annealed sample possesses the highest elongation. That is to say, heat treatment plays different roles in the mechanical properties and corrosion resistance of the experimental alloy.