Al and Al alloys are widely used in industry and technology such as aerospace industry because of their unique properties such as good corrosion resistance, light weight and high mechanical hardness [1] . However, despite their unique properties they are normally brittle. Ductility in this material can be improved by 1) addition of certain amounts of Cu and 2) by change in preparation method to avoid crystallization. Since grain boundaries and defects are the main reasons for brittleness in crystalline materials [2] [3] . On the other hand, ductility can be improved if the material is prepared in the form of amorphous structure. But amorphous phase usually is a meta-stable phase and needs some heat treatment to get more stability provided that the heat treatment is selected carefully [4] [5] . Thermal annealing of amorphous materials can generally make several changes in these alloys. Bulk and surface crystallization, and nanocrystallisation can be imposed on these materials upon thermal annealing [6] -[8] . However low temperature thermal annealing can transfer these alloys to a more stable amorphous state through structural relaxation, enhancing their hardness, ductility and other properties and also increase in density [9] -[11] . In this paper, alloy of Al_(100−x)Cu_x with x = 10, 15, 20 is prepared by evaporation method. Then the prepared specimens were annealed at temperatures 200, 250, and 300˚C for one hour. The value of annealing temperatures is chosen quite low as compared to crystalline temperature to avoid any crystallization due to annealing. XRD of the specimens are taken before and after each thermal annealing to show amorphous nature of the prepared and annealed specimens. Microhardness of the specimens is measured using Vickers method. SEM and AFM also are taken to observe surface morphology of the prepared samples. It is found that for x = 15 and annealing time of 200˚C the maximum hardness is obtained.

Al and Cu are used in the form of powder. The required amount of Al and Cu in the form of powder is used to prepare initial samples. Then by evaporation method in vacuum of 10⁻⁵ torr is deposited on glass substrate. Prepared samples are annealed in vacuum of 10⁻³ torr at temperatures 200, 250 and 300˚C for 1 hour. Structure is characterized using X ray diffraction (XRD) with Cu-K_a radiation with wavelength = 1.5405 angstrom. Microhardness measurements are done using Buehler microhardness tester, with diamond pyramid, load of 10 grams and pressing time of 15 seconds. More than 10 measurements are performed and their average is considered. Jeol SEM is used to observe surface morphology and AFM is used to observe surface roughness of the samples.

The effects of thermal annealing on prepared amorphous samples with composition Al_100−xCu_x were studied using XRD, microhardness tester, SEM and AFM. It is observed that sample with composition Al₈₅Cu₁₅ can give

the best amorphous structure. Thermal annealing at temperature 200 C for one hour can make maximum increase in microhardness of the specimen. And thermal annealing at selected temperatures can relax the specimen and densify it without occurrence of crystallization, hence better ductility can be achieved.