The Evolution of Texture During Annealing of NanocrystallineElectroless Nickel Alloy Deposits

The electroless Ni–Co–P alloy films containing up to 13.4% Co and 7.6% P weredeposited on a 5086 aluminum alloy sheet using baths consisting of NiSO 4 , CoSO 4 ,(NH 4 ) 2 SO 4 , NaH 2 PO 2 , sodium citrate and thiourea. The deposits were solid solutionshaving a grain size of 6–7 nm and strong〈 111 〉texture. When the deposits were annealedfor 2 h, Ni 5 P 2 was precipitated at 325°C and transformed into the stable Ni 3 P phase athigher temperatures. During annealing the texture of deposit changed from〈 111 〉to〈 100 〉 .The texture change was attributed to preferential growth of〈 100 〉grains at the expense of 〈 111 〉grains to decrease the thermal strain energy of the deposits. On the other hand, theelectroless Ni–Cu–P alloy films containing Cu and P deposited on 5086 aluminum alloysheet had the microstructures and textures which are similar to these of the Ni–Co–Palloy films. However, their initial〈 111 〉texture remained relatively stable even afterannealing. The differences in annealing textures of Ni–Co–P and Ni–Cu–P alloy filmshave been discussed.