【作者】 吴忠； 秦真波； 胡文彬；

【Author】 WU Zhong;QIN Zhen-bo;HU Wen-bin;School of Material Science and Engineering,Tianjin University;Tianjin Key Laboratory of Composite and Functional Materials;

【机构】 天津大学材料科学与工程学院； 天津市材料复合与功能化重点实验室；

【摘要】 镍铝青铜合金因其所具有的良好机械性能和耐蚀性能而广泛应用于舰船螺旋桨等海洋装备中。该合金的铸态组织较为复杂,存在着晶粒粗大以及成分偏析等缺陷,在海水环境中容易发生相的选择性腐蚀,加剧空泡腐蚀对材料的破坏。本研究首先采用热处理方法对铸态合金的微观组织进行调控,经退火、正火、淬火和时效处理后获得了不同相组成与形貌的微观组织。然后,针对不同微观组织进行静态腐蚀、力学性能以及空蚀性能测试,建立了微观组织与耐空蚀性能间的关系。研究发现,铸态、退火态以及正火态组织由于相分布的不均匀性,容易发生选相腐蚀,在空蚀作用下局部破坏严重。而淬火以及淬火后450℃时效处理使得组织均匀化,抑制了选相腐蚀的发生;同时,组织中的淬火态β相是Al、Ni元素的过饱和固溶体,在遭受腐蚀过程中表面能够迅速形成保护性较高的腐蚀产物膜层,降低了静态腐蚀速率。此外,该组织具有较高的硬度和强度,能够抵御机械冲击破坏,表现出优异的耐空泡腐蚀性能。但是该组织具有较低的延伸率,对工件进行整体淬火处理会降低其力学性能,造成脆性断裂。综合考虑到合金的腐蚀和机械性能,在保证工件整体力学性能不变的前提下,利用激光表面淬火技术在铸态镍铝青铜合金表面制备得到了具有一定深度的改性层。表层细晶区深度约为220μm,内部显微形貌为类"淬火+450℃时效"组织。相分布均匀,能够消除铸态合金的选相腐蚀,使得腐蚀速率降低约42.5%;表层细晶区分布有较高密度的"核壳"结构纳米析出相,具有较高的硬度和均匀化的组织,机械汽蚀与电化学腐蚀的协同作用较小,使得铸态镍铝青铜合金耐空蚀性能提高了8.8倍。更多还原

【Abstract】 Nickel-aluminum bronze(NAB) alloy is widely used as propeller in marine environments,due to the excellent combination of mechanical properties and corrosion resistance.Grain coarsening and composition segregation defect exist in the cast microstructure.In addition,metallurgically complex microstructures are prone to suffer selective phase corrosion,which aggravate the destruction of cavitation erosion.In this study,the heat treatment method was used to control the microstructure of the as-cast alloy.Microstructures with different phase compositions as well as morphologies were obtained with annealing,normalizing,quenching and aging treatment.and then,static corrosion,mechanical properties and cavitation tests were carried out,and the relationship between microstructure and cavitation corrosion resistance was established.It was found that the as-cast,annealed and normalized structures are prone to selective phase corrosion due to the uneven distribution of phase,and local damage is severe against the attack of cavitation erosion.The quenching and aging treatment at 450°C after quenching made the structure uniform and inhibited the occurrence of selective phase corrosion.While the quenched β phase is a supersaturated solid solution of Al and Ni elements,and its surface could form the protective film quickly during the corrosion process,which reduced the static corrosion rate.In addition,it had high hardness and strength,could resist mechanical impact damage,and exhibited excellent cavitation corrosion resistance.However,the lower elongation with quenching treatment of the workpiece would reduce its mechanical properties and cause brittle fracture.Taking into account the corrosion and mechanical properties of the alloy,the laser surface quenching technology was used to prepare a modified layer with a certain depth on the surface of the as-cast nickel-aluminum bronze alloy.The depth of the fine crystalline region is about 220 μm,whose internal microscopic morphology was similar to the microstructure of quenching/aging at 450℃.Homogeneous distribution of constituent phases eliminated the selective phase corrosion,and reduced the corrosion rate by about 42.5%.There are relatively high-density core-shell nano-precipitates distributed in the fine-crystalline area on the surface.Attributed to high hardness and homogeneous microstructure,the synergy of mechanical erosion and electrochemical corrosion was small,and cavitation corrosion resistance of nickel-aluminum bronze alloy increased by a factor of 8.8.更多还原