17-4 PH stainless steel transforms to martensite during cooling from the solution-treatment temperature and is strengthened by precipitation in the low carbon martensite matrix.
But there has been very little information given to date on the nature of the precipitates in this steel. We made a study on the precipitates by transmission electron microscopy and electron diffraction technique.
The results obtained are summarized as follows:
(1) The precipitate is fcc copper rich phase with a lattice parameter of 3.595-3.600 A.
(2)On prolonged aging, the precipitate grows into a rod with its longitudinal direction parallel to ‹111› martensite matnx.
The precipitate-martensite matrix orientation relationship is similar to the Kurdjurnov-Sachs relationship, i.e. (111)ppt//(110)matrix [110]ppt//[111]matrix.
