| Cu-Ni-Al alloys are copper-based alloys, which have been widely used in civilianindustry and military. Currently, the application concentrates on the wrought Cu-Ni-Al alloyswith low content of Ni and Al. In this paper, the effect of minor alloying elements on themicrostructures and properties of Cu-17Ni-3Al alloy (hereinafter referred to as X alloy) wereinvestigated by tensile tests, friction and wear tests, optical microscope, scanning electronicmicroscope, X-ray diffraction and transmission electronic microscope. The main conclusionsare summarized as follows:The microstructure character of X alloy was studied. The result shows that the X alloyhas a typical dendrites microstructure with some sheet and granular Ni3Al phase distributed atits grain boundaries and interdendritic spaces. The granular Ni3Al phase also exists in thematrix of the X alloy.The effect of adding Fe、Cr、Si、Mn separately on secondray dendrite arm spacing and thesecond phases of the X alloy was investigated. The result shows that Fe、Cr、Si、Mn canrefine the secondary dendrite arm spacing. Adding Fe and Mn separately would not changethe morphology and type of the second phases, which were respectively regarded as Ni3(Al,Fe)and Ni3(Al,Mn). The addition of Cr would form plate-like, rod-like, lump-like Cr phase andinhibit the formation of the Ni3Al phase at the grain boundaries and interdendritic spaces ofthe X alloy. The addition of Si would form a bone-shape Si-rich phase, which distributes onthe surface of the Ni3Al phase. In addition, Adding Fe、Cr、Si、Mn separately would notchange the type of granular second phase in the matrix.The effect of adding two elements simultaneously on the second phase of X alloy wasstudied. Adding Fe and Mn to the X alloy would change the morphology and composition ofthe second phase and also form the rod-like Ni3(AlFeMn). Adding Fe and Cr to the X alloycould inhibit the formation of Ni3Al phase at grain boundaries and interdendritic spaces, whileit would form the plate-like and braise-like Fe-rich Cr phase and Fe-poor Cr phase, which arerod-like or chunk-like. Adding Fe and Si simultaneously to the X alloy shows the similiar second phase compared with the addition of Si solely, but the number of second phase in theformer is smaller than that of the later.The effect of adding three elements simultaneously on the second phase of X alloy wasstudied. The simultaneous addition of Fe, Cr, Mn or Fe, Cr, Si have the same morphologies ofthe second phases, plate-like and braise-like Fe-rich Cr phase and rod-like or chunk-likeFe-poor Cr phase, which were similar to the alloy with additive elements of Fe and Cr. Inaddition, a rod-like Si-rich phase could be found in the alloy with additive elements of Fe、Si、Cr. Also, a complicated phase which rich in Ni、Si、Al、Fe was found in the alloy with thesimultaneous addition of Fe、Si and Mn.The effect of adding Fe、Cr、Si、Mn elements sequently on the mechanical properties ofX alloy was studied. It shows that adding alloying elements could improved the tensilestrength, yield strength and brinell hardness in different degree. The mechanical properties ofthe X alloy, X-Fe-Cr-Si alloy and X-Fe-Cr-Si-Mn alloy increased in turn, which wereattributed to the integrate effect of the refined crystalline strengthening, solution strengtheningand the second phase strengthening caused by adding the alloying elements. On the contrary,adding alloying elements would weaken the ductility of the X alloy and the X-Fe-Cr-Si-Mnalloy has the worst ductility.The friction and wear properies of the alloys with adding the alloying elements wereinvestigated in the dry friction condition. The average friction coefficient, wear volume, weardepth and wear superficial area all decreases when adding alloying elements. The abrasionperformance of the X alloy, X-Fe alloy, X-Fe-Cr alloy, X-Fe-Cr-Si alloy and X-Fe-Cr-Si-Mnalloy increases in sequence. In dry friction condition, both adhesive wear and abrasive wearexists at the friction process of the all the alloys. |
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