J.H. Han

Formation of a bimodal eutectic structure in Ti–Fe–Sn alloys with enhanced plasticity

Microstructural investigations on a series of (Ti70.5Fe29.5)100−xSnx alloys with x=5, 7, and 9 reveal that Sn addition is effective in introducing both structural and spatial heterogeneities in ultrafine eutectic composites stemming from a large temperature difference between two eutectic temperatures upon solidification. The microstructural heterogeneities in these ultrafine eutectic composites strongly enhance the room temperature compressive plasticity up to ∼15.7%.

Influence of a bimodal eutectic structure on the plasticity of a (Ti70.5Fe29.5)91Sn9 ultrafine composite

Systematic investigations on the microstructural evolution of a bimodal eutectic (Ti70.5Fe29.5)91Sn9 ultrafine composite containing Ti3Sn dendrites upon compression reveal that local deformation of the dendrites dominates the early stage of deformation with a plastic strain of ep=5.8%. After further deformation (ep=10.2%), a wavy propagation of shear bands indicative of dissipation of the shear stress is caused by a rotation of the coarse eutectic structure along the interfaces of the bimodal eutectic structure.

Favorable microstructural modulation and enhancement of mechanical properties of Ti–Fe–Nb ultrafine composites

Microstructure evolution and its influence on the mechanical properties of (Ti65.5Fe34.5)100− x Nb x (x = 0, 3, 5 and 7) ultrafine composites has been investigated. The Nb-containing alloys exhibit simultaneously improved compressive mechanical properties, i.e. high yield (1.9–2.2 GPa) and fracture (2.2–2.6 GPa) strength together with large plasticity (6–13%), due to a favorable modulation of their ultrafine eutectic microstructure. The enhanced mechanical properties are strongly related to the length-scale, volume fraction and distribution of proeutectic phase as well as to the refinement and interphase coherency of the alternating ultrafine eutectic layers.

High strength porous Ti?6Al?4V foams synthesized by solid state powder processing

We demonstrate a powder metallurgy synthesis route for porous Ti?6Al?4V structures by consolidation of Ti?6Al?4V alloy powders and describe the influence of the processing conditions. Ti?6Al?4V foams with 50?vol% porosity having high strength were fabricated by low temperature solid state deformation at temperatures below 873?K. The open cellular structure consists of continuously connected Ti?6Al?4V struts and homogeneously distributed pores with nominal diameters between 10 and 50??m and 150?500??m length.

MICROSTRUCTURAL EVOLUTION AND MECHANICAL PROERTIES OF Ti-(Ni, Fe)-Sn ULTRAFINE EUTECTIC ALLOYS

Ultrafine eutectic alloys have been developed in Ti-Ni, Ti-Fe and Ti-(Ni, Fe)-Sn alloys. The Ti76Ni24 and (Ti74Ni26)97Sn3 ultrafine eutectic alloys consist of a mixture of α-Ti and Ti2Ni phases, and β-Ti(Sn) and Ti2Ni phases, respectively, whereas the Ti70.5Fe29.5 and (Ti70.5Fe29.5)97Sn3 alloys are composed by a mixture of β-Ti(Sn) and FeTi phases with relatively spherical colony. The compression tests of Ti76Ni24, (Ti74Ni26)97Sn3 and Ti70.5Fe29.5 ultrafine eutectic alloys reveal a strength of 1400 ~ 1800 MPa with very limited plastic strain of 0.1 ~ 1%. On the contrary, a (Ti70.5Fe29.5)97Sn3 alloy exhibits high strength of 2270 MPa with enhanced plastic strain of 3.1%. Based on these results, it is feasible to suggest that the eutectic morphology and interfacial coherency between the Ti solid solution and intermetallic phases influence to control the macroscopic plasticity of the Ti-Ni and Ti-Fe ultrafine eutectic alloys.