Unraveling The Tailoring Mechanisms Of Electrodeposition Parameters On The Microstructure And Mechanical Properties Of Nanocrystalline Nickel Coatings

In this paper,the combined effects of deposition parameters,namely current density,bath temperature and electrolyte p H on morphology,structure and mechanical properties of nanocrystalline nickel(nc-Ni)coatings have been explored.The links between grain size,texture,surface quality and their consequence on indentation behavior have been examined.A direct correlation between grain size and texture is established for the first time.Grain size along(111)orientation decreases with texture coefficient ignorance of deposition conditions,as a contrast the grain size along(220)orientation almost remains unchanged when changing current density or p H,while it increases with texture when changing temperature.For nc-Ni coatings with fcc structure,the grain size along(111)direction is largest comparing with that along other orientations.Bath temperature has great influence on the grain size,and p H has minor effect.However,texture formation is sensitive to process parameters.Secondly,the relationship between hardness and grain size can not totally be described by the simple Hall-Petch effect,but has more underlying mechanisms in relation to texture and surface quality.The dependence of grain size on hardness is accurately described by the Hall-Petch relationship in the case of changing temperature or p H value with different slope,while it breaks down when changing current densities.The microhardness discrepancy from the Hall-Petch relation can be principally depicted from texture formation and compactness of deposits.The Hall-Petch slope depends on texture formation in relation to the distribution of grain boundaries controlled by process parameters.Thirdly,the elastic modulus of coatings decrease with increasing temperature,while it is less affected by p H but has complicated relationship with current density.The elastic modulus v.s.process parameters revealed here can be tentatively explained by considering the superposition effects of grain size,texture formation and surface quality.Texture formation prevails over other two factors on elastic modulus denoting the impor tance of elastic anisotrophy.The overall results provide a novel advance in understanding the basic mechanisms of electrodeposition.