Abstract
During the high pressure die casting process (HPDC), it is necessary to develop new designs and alloys for the copper plungers. In this research, two alloys Cu-9Ni-1Co-1.6Cr-2Si-1.3Fe-0.25B wt.% (A1) and Cu-9Ni-1Co-1.6Cr-2Si-0.1Fe-0.2Nb wt.% (A2) under different heat treatments (HT) were studied. Optical microscopy technique was applied to reveal the regions of dendritic morphology, also lower Secondary Dendrite Arm Spacing (SDAS); and different grain orientations. The results reveal that the solidification sequence is primary Cu dendrites and secondary intermetallics; heat treatments increase the redistribution of alloying elements in the interdendritic regions. During the heat treatments, some precipitates were found in the grain boundary after aging heat treatments for both alloys, which were determined by X-ray diffraction. Hardness test HRB presented a decrease with the solution heat treatment and an increase with the aging heat treatments proposed for both alloys. Finally, the wear resistances for both alloys were compared with a commercial alloy C17530, with decreased A1 with B additions having the best result in the as-cast condition 4.07 × 10−4 mm3/Nm, while for A2 with Nb additions wear resistance increased, with the best result in the one with aging heat treatment 1.69 × 10−4 mm3/Nm while for the C17530 alloy this was 2.74 × 10−4 mm3/Nm.
Highlights
Copper increases its performance, such as electrical resistance, when it is alloyed with different elements [1]; alloys such as Cu-Ni-Si have been used in electrical applications due to their excellent electrical conductivity and mechanical stress properties [2]
Band Nb additions on alloys Cu-9Ni-1Co-1.6Cr-2Si-1.3Fe-0.25B wt.% (A1) and A2 alloys with a solution treatment and two aging were studiedin order to understand the effects on the microstructure and properties, conclusions are summarized order to understand the effects on the microstructure and properties, conclusions are summarized as as follows: follows:
There is an evolution of the microstructure due to B and Nb additions and heat treatments;
Summary
Copper increases its performance, such as electrical resistance, when it is alloyed with different elements [1]; alloys such as Cu-Ni-Si have been used in electrical applications due to their excellent electrical conductivity and mechanical stress properties [2]. Mechanical properties for Cu-Ni-Si alloys can be improved by additions of other elements; Al [4] and Mg [5] improve solidification kinetics and intermetallic precipitations; Ti can refine the microstructure due to the reduction of solubility of Ni and Si in the copper matrix [6]; Cr can refine the structure by precipitation of Cr3 Si particles [7]; Zr [8] and V [9] can modify the microstructure and improve the performance of aging heat treatment; Co [10] additions affect microstructure and increase hardness by aging heat treatment. Aging heat treatment is made by a previous solid solution heat treatment after casting the alloy; the more elements in solution, the higher the hardness and mechanical resistance [16]
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