Effects of processing parameters on relative density, microhardness and microstructure of recycled Ti–6Al–4V from machining chips produced by equal channel angular pressing

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 651; pp. 248 - 258
• Main Authors: Shi, Q., Tse, Y.Y., Higginson, R.L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10-01-2016
• Subjects: Chips; Density; Equal channel angular pressing; Grains; Machining; Machining chip; Microhardness measurement; Microstructural characterization; Microstructure; Recycled; Recycling; Titanium base alloys; Ti–6Al–4V; Microstructural characterization; Microhardness measurement; Ti–6Al–4V; Machining chip; Recycling; Equal channel angular pressing
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2015.11.002

Ti–6Al–4V was recycled from machining chips by using equal channel angular pressing (ECAP). Samples were pressed through a die up to 8 passes at moderate temperatures in the range of 400–500°C. The ECAP process was accomplished with back-pressures ranging from 50 to 250MPa. The results demonstrate that ECAP with back-pressures allows the consolidation of machining chips to near fully dense (~99.9%) recycled products. The relative density of the as-recycled samples increased with the applied back-pressure and number of passes. The average hardness and homogeneity were improved as the number of passes increased. The transmission electron microscopy reveals a combination of equiaxed and elongated α grains after the first pass. With subsequent pressing, the samples were dominated by nano-equiaxed α grains with diameters of ~70nm. The original β phase in the machining chips was fragmented during the ECAP process.