A chromosomal duplication is what occurs at phase S of the interphase, the result of this process is a new copy of the chromosome in order to prepare for cell division, when one chromosome will lead to each daughter cell, which will have the same genetic material after mitosis.
On the other hand, chromosomal translocation is when a segment of DNA moves to another place in the genome, what may cause genetic diseases or not, depending on where it is moved or if there is some information lost.