In this paper, WC-Al composite coatings of AZ91 alloy prepared by mechanical alloying have been investigated in detail. It was found that the premixing process of composite powders has no significant effect in promoting the formation of uniform coating of WC-Al powders. Under the optimised conditions, i.e. the composition of composite powders of (10 g WC-6?5 g Al-3 g AZ91-0?5 g Mg), ball-to-powder weight ratio of 14 : 1 and milling duration of 12 h, the average thickness of composite coating can be remarkably increased to 38?01 mm. Compared with the bare substrate, the Brinell hardness of the specimen with WC-Al composite coating can be significantly increased by about 90?01%.

Analysis of LEED intensities of thin films of Ni grown epitaxially on bcc FeJ001 1 establishes that the structure is bcc up to six layers, but with a contraction of 5 % of the first layer spacing and expansion of 5% of the second layer spacing. At thicknesses above six layers there is a gradual change to a new surface and bulk structure with increasing disorder. Spin-polarized total-energy band calculations show that the bcc Ni film is stretched 1.4% from its equilibrium value and thereby changed from nonmagnetic to ferromagnetic. The calculated results on stable and metastable phases of Fe, Co, Ni and Cu show that the equilibrium lattice parameters and differences in binding energies favor mutual epitaxy for any bcc or fcc pair. There are six pairs in which a possible metastable phase is grown epitaxially on a stable substrate.