高エネルギー遊星ボールミルによるAl-6 at%Ti混合粉末のメカニカルアロイング過程

Abstract

The mechanical alloying(MA) process of Al-6 at%Ti mixed powders under a surging mode of a high energy planetary ball mill in Ar gas, at the maximum centrifugal acceleration of 40, 80, 120 and 150 G(G is the gravitational acceleration), was investigated by means of microscopic observation, X-ray diffraction, hardness measurement and quantitative analysis of the composition. The MA process proceeds in the following three stages; At the 1st stage both the coalescence of Al and Ti elemental powders and adhering on the pot-wall and the surface of balls occur. The amount of such adhesions increases with milling time. At the 2nd stage, almost all Al-Ti mixed powders adhere on the pot-wall and the ball surfaces, and the dissolution of Ti and Fe atoms into Al powders, work-hardening and the refining of the crystal grains to the nano-size proceed under compressional, frictional and shearing stresses, due to the surging motion of the milling balls. At the 3rd stage, the hardened(Hv: 400∼500) powders, consisting of nano-size crystals of Al-6 at%Ti-1 at%Fe supersaturated solid solution, fall down from the pot-wall and the ball surfaces during milling. In the 3rd stage, the higher the MA energy, the larger the amount of the powders obtained and the greater the hardness of the powders. At the same time, the higher milling intensity caused the faster progress of the MA process. The average grain size of the Al-6 at%Ti-1 at%Fe alloy powders milled for a long time is from 13 to 17 nm, depending on milling intensity during MA. Higher milling intensity tends to bring a smaller grain size. No amorphous phase is detected.