Processing-structure relationship in open die hot forged W-Hf-Ti

The processing-structure relationship in a series of presintered W-Hf-Ti alloys open die hot forged at 1,300--1,350 C has been examined. The alloys were prepared with W levels varying from 60--95 wt% while keeping the Hf/Ti ratio constant at 1:3. The alloys were fabricated from elemental powders by mechanical mixing, cold isostatic pressing and sintering at 1,500 C before open die hot forging. Other alloy compositions within this W range were also produced to determine if altering the Hf and Ti ratio to 1:2 and 1:1 had any effect on the microstructures produced after hot forging. Microstructural observations using optical microscopy and scanning electron microscopy revealed that the structures were composed of a complex mixture of 3 microconstituents in the high-W containing alloys. W grains were typically surrounded by a thin layer composed of a less W-rich phase containing some Ti. It appeared as if this less W-rich layer (in several of the compositions) isolated the W particles from each other. Interspersed among these W-rich phases was a Ti-rich phase which contained a very fine dispersion of W-rich particles. X-ray diffraction experiments confirmed that a W solid solution and a Ti solid solution were present in each alloy. In addition, W2Hf was detected in the alloys that had a Hf/Ti ratio of 1:2 and 1:1