Among various light-weight materials, aluminum is one of the first candidates for structural materials to be widely used for housing, vehicles or machinery parts. Although the anodizing processing, or, surface hardening methods, are effective for conventional usage of aluminum alloys, a wide usage of aluminum alloys in the engineering fields requires advanced surface treatment and surface modification approach. Plasma nitriding is one of the most promising ways to make surface structuring for various aluminum alloys. New plasma nitriding method is proposed to effectively synthesize aluminum nitride layer without use of argon sputtering. This method is composed of the nitrogen pre-sputtering and the nitriding with use of nitrogen - hydrogen mixture gas. AlN formation process is described by using the pure aluminum cast samples. In order to understand the effect of grain boundaries on the nitriding process, the grain size was refined by the bulk mechanical alloying (BMA). Furthermore, Ti-bearing aluminum alloy was prepared by BMA to investigate the micro-alloying effect on the nitriding process.