Evolution of microstructure and mechanical properties of Ti/TiB metal-matrix composite during isothermal multiaxial forging

Abstract

Mechanical behavior and microstructure evolution of a Ti/TiB metal-matrix composite during multiaxial forging (MAF) at 700 and 850 C and a strain rate 10 À3 s À1 were studied. The composite was produced via in-situ 3Ti þ TiB 2 /2Tiþ2TiB reaction during spark plasma sintering at 1000 C. Mechanical behavior in terms of aggregated s-Sε curves during MAF at both temperatures demonstrated a pronounced softening following by a steady-like flow stage. Microstructure evolution during MAF at both temperatures was associated with (i) dynamic recrystallization of the titanium matrix and the formation of dislocation-free areas of~1 mm in diameter and (ii) shortening of TiB whiskers by a factor of~3. MAF at 700 and 850 C to cumulative strain~5.2 resulted in a considerable increase in the low-temperature ductility without substantial loss in strength. Contributions of different strengthening mechanisms into the overall strength of the Ti/TiB metalematrix composite were discussed.

Mechanical Behavior and Microstructure Evolution of a Ti-15Mo/TiB Titanium–Matrix Composite during Hot Deformation

“…Since some improvement in mechanical properties can be attained in the composites through hot/warm working [14,29], the obtained results on mechanical behavior during hot deformation were used to determine the optimal processing window. The temperature-strain rate map in Figure 7 shows domains where deformation capacity of the composite was high enough for hot/warm working (i.e., areas associated, for example, with superplasticity or dynamic recrystallization).…”

“…Hard fibers of TiB increase the strength and hardness of TMC, however the ductility of the composite can decrease to nearly zero [9,10]. Some improvement in both ductility and technological properties was attained in thermomechanically treated TMCs [11][12][13][14][15][16][17] due to the shortening and redistribution of TiB whiskers, along with the development of dynamic recrystallization in the titanium matrix. Another promising way to improve ductility of the composite can be associated with an increase in plasticity of the titanium matrix by adding a β-stabilizing element.…”

Effect of Hot Rolling on the Microstructure and Mechanical Properties of a Ti-15Mo/TiB Metal-Matrix Composite

“…Some increase in ductility of Ti/TiB composites can be attained via thermomechanical treatment [11][12][13][14]. For example, the ductile-to-brittle transition temperature of a Ti-17 vol.% TiB composite was noticeably decreased due to warm multiaxial forging (MAF) [13,14]. However, room temperature ductility of warm/hot worked composites with ~17 vol.% TiB reinforcements was found to be low [15].…”

“…Meanwhile, achieving considerably increased strength and hardness of Ti/TiB composites results in loss in ductility, even in the case of a relatively low amount of reinforcements [10]. Some increase in ductility of Ti/TiB composites can be attained via thermomechanical treatment [11][12][13][14]. For example, the ductile-to-brittle transition temperature of a Ti-17 vol.% TiB composite was noticeably decreased due to warm multiaxial forging (MAF) [13,14].…”

Effect of Heat Treatment on Creep Properties of in situ Synthesized (TiB+La2O3)/Ti Composite

“…Especially on the investigation of microstructural evolution during the creep deformation process. It is important for understanding the creep properties determined by the forming and heat treatment (Hosseini et al, 2017;Ozerov et al, 2019). The bimodal microstructure consists of equiaxed α grains and α+β colonies, creep strain rates reduce with equiaxed α decreasing in bimodal microstructure during primary and secondary creep.…”