ABSTRACT
Mechanical alloying (MA) is a complex process involving optimization of a number of process variables to achieve the desired product phase, microstructure, and/or properties. However, we will not consider the nature and composition of the powder mix as a variable here. These will decide the nature of the phase formed (solid solution, intermetallic, or amorphous phase, etc.) in the milled powder, and discussion about these is presented in subsequent chapters. For a given composition of the powder, some of the important variables that have an important effect on the final constitution of the milled powder are as follows:
Type of mill Milling container Milling energy/speed Milling time Type, size, and size distribution of grinding medium Ball-to-powder weight ratio Extent of vial filling Milling atmosphere Process control agent Temperature of milling
These process variables are not completely independent. For example, the optimal milling time depends on the type of mill, size of the grinding medium, temperature of milling, ball-to-powder ratio (BPR), etc. Further, more energy could be imparted to the milled powder by increasing the BPR or bymilling the powder for a
MD: SURYANARAYANA, JOB: 03320,
longer time. Similarly, it could be shown that some of the other parameters are also interdependent. Even so, we will discuss in the following paragraphs the effect of these variables on the final product obtained after MA assuming mostly that the other variables have no significant effect on the specific variable being discussed.
