Precipitate phases and mechanical properties of heat-treated ASTM F 9o Co-Cr-W-Ni alloy

摘要

The precipitation behavior during heat treatment and resulting mechanical properties of ASTM F 90 Co-20Cr-15W-10Ni (mass%) alloys were investigated with regards to their biomedical applications. Heat treatment was conducted at temperatures of 873 to 1623 K, for a holding time of 259.2 ks. The precipitates produced were then electrolytically extracted from the alloys and analyzed by X-ray diffraction (XRD). This revealed that the precipitates formed were an M_23X_6 type and/or n.-phase (i.e., an M_6X-M_12X type). The M_23X_6-type precipitate was detected across the entire heat-treatment temperature range; however, the ri-phase precipitate was only detected at 1073 to 1473 K, becoming dominant at 1173 to 1373 K. The formation of M_23X_6 type precipitates at 873 K is shown to improve the mechanical properties of this alloy, whereas the domination by the r|-phase precipitate at higher temperatures causes deterioration in the ductility.