Influence Of Co On The Microstructure And Wear Behavior Of High-aluminum Bronze

High-Al bronze Cu-14Al-X is an excellent corrosion resistance and wear resistance alloy which was developed by the researchers in our laboratory. This article probes into influences of Co element on as-cast and past heat treatment microstructure, and wear behaviors of this high-Al bronze.As-cast and past heat treatment microstructures of the high-Al bronze samples with different mass fraction of Co were observed and analyzed by MEF3, XRD and EPMA, etc. The results indicated that :(1) After increase of wt % Co, as-cast microstructure of the alloy changed obviously, cinquefoil shapes new phase appeare. (2) Formation of k phase can be promoted evidently by Co element in the alloy, with the increase of wt % Co, composition of k phase changed, most Co dissolves in k phase. (3) After oil-quenched at 920°C×3h, the eutectoid phase in the high-Al bronze started to dissolve and reduce gradually, cinquefoil phase transformed from cinquefoil into round. (4) After aged at 580 °C × 5h, Al, Co, Fe, Mn elements which contained in the copper matrix aggregated again and grew into cinquefoil phases during the aging period, also the eutectoid phases was separated out diffusively, strength performance of the alloy was enhanced under a dispersion strengthening regularly.Dry friction wear behaviors of the high-Al bronze with different mass fraction of Co were examined in pin-on-bar reciprocating device. Results shown that: (1) After increase of wt % Co, under the low speed and load condition, wear extent of the alloy rose at first but reduced after that, wear behaviors under such condition present as typical low stress abrasive wear, oxidative wear and light fatigue wear. Under the medium speed and load condition, wear extent of the alloy reduced at first but rose after that, wear behaviors under such condition present as high stress abrasive wear, oxidative wear and severe fatigue wear. (2) Composition and microstructures of the alloy have main influences on wear behaviors of this high-Al bronze, due to the existence of K phase hard particles, diffusive distribution of γ₂ and K phases enchased into β'+(α+β) matrix phase, hardness of the alloy rise and consequently the resistance of deformation of circular plastic was enhanced, which cause a good wear resistance.