Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

Abstract

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti₂Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti₂Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which is attributed to the presence of precipitate-free zones formed along grain boundaries during semisolid processing.

Keywords

titanium alloys / semisolid / forging / microstructure / precipitates / mechanical properties

References

[1] Donachie MJ. Titanium: a Technical Guide, 2000, Michigan, ASM International, Materials Park, 22.

[2] Ho WF. A comparison of tensile properties and corrosion behavior of cast Ti-7.5Mo with c.p. Ti, Ti-15Mo and Ti-6Al-4V alloys. J. Alloys Compd., 2008, 464(1–2): 580.

[3] Eskin DG, Suytino Katgerman L. Mechanical properties in the semi-solid state and hot tearing of aluminum alloys. Prog. Mater. Sci., 2004, 49(5): 629.

[4] Phillion AB, Thompson S, Cockcroft SL, Wells MA. Tensile properties of as-cast aluminum alloys AA3104, AA6111 and CA31218 at above solidus temperatures. Mater. Sci. Eng. A, 2008, 497(1–2): 388.

[5] Chino Y, Kobata M, Iwasaki H, Mabuchi M. An investigation of compressive deformation behaviour for AZ91 Mg alloy containing a small volume of liquid. Acta Mater., 2003, 51(11): 3309.

[6] Hu K, Phillion AB, Maijer DM, Cockcroft SL. Constitutive behavior of as-cast magnesium alloy Mg-Al3-Zn1 in the semi-solid state. Scripta Mater., 2009, 60(6): 427.

[7] Mohamed R, Mitsuharu T, Hiroyuki N. Effect of semi-solid processing on solidification microstructure and mechanical properties of gray cast iron. Mater. Sci. Eng. A, 2006, 417(1–2): 166.

[8] Püttgen W, Hallstedt B, Bleck W, Löffler JF, Uggowitzer PJ. On the microstructure and properties of 100Cr6 steel processed in the semi-solid state. Acta Mater., 2007, 55(19): 6553.

[9] Sun QY, Yu ZT, Zhu RH, Gu HC. Mechanical behavior and deformation mechanisms of Ti-2.5Cu alloy reinforced by nano-scale precipitates at 293 and 77 K. Mater. Sci. Eng. A, 2004, 346(1–2): 159.

[10] Chen CP, Tsao CYA. Semi-solid deformation of non-dendric structures: I. Phenomenological behavior. Acta Mater., 1996, 45(5): 1955.

[11] Nie JF. Effects of precipitate shape and orientation on dispersion strengthening in magnesium alloys. Scripta Mater., 2003, 48(8): 1009.

[12] Chen YN, Wei JF, Zhao YQ. Compressive defor mation and forging behavior of Ti14 alloy in semi-solid state. Mater. Sci. Eng. A, 2009, 520(1–2): 16.

[13] Chen YN, Wei JF, Zhao YQ, Sun J. Effect of semisolid forging temperature on microstructure and mechanical properties of Ti14 alloy. J. Alloys Compd., 2009, 487(1–2): 314.

[14] Zhao YQ, Wu WL, Ma XD, Chang H, Yang HY, Wu H, Feng L. Semi-solid oxidation and deformation behavior of Ti14 alloy. Mater. Sci. Eng. A, 2004, 373(1–2): 315.

[15] Zhao YQ, Wu WL, Chang H. Research on microstructure and mechanical properties of a new α+Ti₂Cu alloy after semi-solid deformation. Mater. Sci. Eng. A, 2006, 416(1–2): 181.

[16] Zhao YQ, Zhu KY, Li Y. A Low Cost Ti Alloy, 1997

[17] Zhao YQ, Zhu KY, Li Y. A Low Cost Near β-Ti Alloy, 1997

[18] Iwasaki H, Mori T, Mabuchi M, Higashi K. Shear deformation behavior of Al-5% Mg in a semi-solid state. Acta Mater., 1998, 46(18): 6351.

[19] Li YG, Loretto MH, Rugg D, Voice W. Effect of heat treatment and exposure on microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C (wt%). Acta Mater., 2001, 49(15): 3011.