DEVELOPMENT OF PARTICLE MORPHOLOGY DURING DRY BALL-MILLING OF CU POWDER

Tumbler-ball milling experiment was carried out to investigate the cha nge in particle morphology involved in the mechanical alloying of duct ile metal powders using Cu powder as a model material. The morphologic al evaluation of the milled particles was traced by microscopic observ ations and by a shape analysis made on particle cross sections. It was found that during milling the particle shape of Cu powder changes fro m initial dendritie to disk-shape, then to coagulated pancake and even tually to large equi-axed globular particles. The globular particles w ere found to be formed by agglomeration of the disk-shaped particles i n a characteristic manner. It was also found that the large globular p articles were formed by the agglomeration of the globular particles. T he disk-shaped particles were supposed to be formed by breaking-off of sticked layer on ball surfaces and mill container walls by the impact actions of milling balls. The diameter of the disk-shaped particles e stimated from the impact velocity of the balls based on the milling-ba ll dynamics and the Hertz contact theory is in good agreement with the measured one.