Association of Metallurgical Engineers of Serbia (AMES), Beograd
Abstract
The precipitation behavior of W-rich phase on the specific matrix locations of
Co-free and Co-containing 92.5W-5Ni-2.5Fe heavy alloys is investigated during
aging of the as-quenched samples. The aging treatment is performed between 600
°C (873 K) and 800 °C (1073 K) and for aging time up to 9 hours. The average
chemical composition of tungsten heavy alloys was determined by using the atomic
absorption spectrophotometry (AAS) and the Leco apparatus. The Energy
Dispersive X-ray (EDX) analysis was employed to analyze the chemistry of the
existing phases. The changes in structure as a function of aging time and
temperature have been examined by using the light microscopy (LM) and the
scaning electron microscopy (SEM). The macro- and micro-hardness
measurements were performed, as well. The local changes in matrix structure and
various morphologies of the precipitates are observed. The aging has caused only
a minor changes of the micro-hardness of the existing phases (γ and W-rich) as
well as the macro-hardness of the investigated alloys. In the case of the Co-free
92.5W-5Ni-2.5Fe heavy alloy, at lower temperatures and for shorter time of aging,
there is a dominant presence of lamellar and Widmanstätten morphology of W-rich
precipitates within the γ-matrix grains. At higher temperatures and for longer time,
there is a significant precipitation of W-rich precipitates at the matrix grain
boundaries (γ/γ). In the case of 92.5W-5Ni-2.5Fe heavy alloy micro-alloyed with
Co, it is dominant precipitation of W-rich phase at the matrix grain boundaries (γ/γ),
especially at higher aging temperatures and for longer aging time