Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1605980 | Journal of Alloys and Compounds | 2016 | 10 Pages |
Abstract
The Fe-Cr-Ti-Nb elemental powders were mechanically alloyed/ball milled with TiB2 and a small quantity of Y2O3 ceramic to synthesize a novel Fe-based alloy-ceramic powder composite that could be processed by hot isostatic pressing (HIP) for a perceived potential application as a neutron absorber in nuclear reactors. After ball milling for the 30-80 h duration relatively uniform powders with micrometric sizes were produced. With increasing milling time a fraction of TiB2 particles became covered with the much softer Fe-based alloy which resulted in the formation of a characteristic “core-mantel” structure. For the final HIP-ing process the mechanically alloyed powders were initially uniaxially pressed into rod-shaped compacts and then cold isostatically pressed (CIP-ed). Subsequently, the rod-shaped compacts were placed in the Ti-tubing and subjected to hot isostatic pressing (HIP) at 1150 °C/200 MPa pressure. The HIP-ing process resulted in the formation of the near-Ti and intermediate diffusional layers in the microstructure of HIP-ed samples which formed in accord with the Fe-Ti binary phase diagram. Those layers contain the phases such as α-Ti (HCP), the FeTi intermetallic and their hypo-eutectoid mixtures. In addition, needle-like particles were formed in both layers in accord with the Ti-B binary phase diagram. Nanohardness testing, using a Berkovich type diamond tip, shows that the nanohardness in the intermediate layer areas, corresponding to the composition of the hypo-eutectoid mixture of Ti-FeTi, equals 980.0 (±27.1) HV and correspondingly 1176.9 (±47.6) HV for the FeTi phase. The nanohardness in the sample's center in the areas with the fine mixture of Fe-based alloy and small TiB2 particles equals 1048.3 (±201.8) HV. The average microhardness of samples HIP-ed from powders milled for 30 and 80 h is 588 HV and 733 HV, respectively.
Related Topics
Physical Sciences and Engineering
Materials Science
Metals and Alloys
Authors
PrzemysÅaw Litwa, Krzysztof Perkowski, Dariusz Zasada, Izabela Kobus, Gustaw Konopka, Tomasz Czujko, Robert A. Varin,