采用化学镀方法在AZ91D压铸镁合金表面获得Ni-P镀层,研究了不同热处理温度对镀层的组织和性能的影响.结果表明:镍层中P含量为6.22 wt%,镀层组织为非晶+少量纳米晶组织.随热处理温度升高原始镀层中的非晶组织中先形成镍纳米晶,然后纳米晶镍伴随晶化过程进行迅速长大,并在镍基体上析出Ni_(12)P_5和Ni_3P相.镀层与基体的结合强度在350℃附近达最大结合强度为3.7 MPa,镀层硬度在400℃附近达最大值为825 HV;盐雾腐蚀实验表明镀层耐腐蚀性能良好,连续盐雾8 h未出现腐蚀斑点.经过不同的热处理,镀层的耐蚀性随着热处理温度的提高而下降.
The Ni-P plating was prepared on AZ91D magnesium alloy by eleetroless deposit. The effect of heat treatment temperatures on the microstructure and property of the Ni-P deposit was investigated by means of SEM,XRD,TEM,microhardness test and spray corrosion tests. The results show that the plating with 6. 22 wt% phosphorus consists of amorphous and nanocrystalline microstructure. Nanocrystalline nickel forms firstly in the amorphous during annealing. The grain sizes of the nickel grow rapidly during crystallization. Ni_3P and a little of Ni_(12)P_5 phases form in nickel matrix of the deposited coating after annealing. The maximium adhesion strength of 3.7 MPa is obtained for the deposited coating annealed at 35℃. The maximum hardness of the coating is 825 HV when annealing the temperature reachs 400 ℃. The salt spraying test shows that good corrosion resistance of the plating is observed,however,the corrosion resistance gradually declines with increasing annealing temperature.
参考文献
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