Microstructure and Properties of New Ti–Al–Fe–Cr Transition Class Alloy Produced by Blended Elemental Powder Metallurgy Using TiH2 and Master Alloy

Abstract

Blended elemental powder metallurgy using titanium hydride and Al-Fe-Cr master alloy powders was employed to produce a new Ti-1.5Al-1Fe-7.2Cr (wt.%) transition a ? b/b metastable-type alloy. A simple process involving blending, cold pressing, and sintering resulted in a material with a residual porosity of not higher than 3.9-5%, a uniform and relatively fine-grained microstructure (average b-grain size of less than 100 lm), and acceptable mechanical properties. The influence of subsequent annealing and hot pressing on the microstructure evolution and porosity reduction was investigated. The results indicated that optimized regimes of hot deformation and heat treatment produced a structural state with a good combination of strength (UTS = 970 MPa) and ductility (El = 14.7%, RA = 35%).Keywords Low-cost titanium alloy Á Microstructure Á Mechanical properties Á Blended elemental powder metallurgy Á Thermomechanical treatment Á Fracture Á Phase composition

Microstructure and Tensile Properties of Cost-Efficient Thermally Hardenable α + β Alloys of Ti–Al–Mo–Fe and Ti–Al–Mo–Cr Systems

“…2b). The regimes of subsequent thermomechanical processing and heat treatments were chosen basing on the technological approaches developed in [16,[22][23][24]. Machined semiproducts were subjected to 3D pressing at initial temperature of 1100 °C (Fig.…”

“…The results of tensile tests of all program materials are presented in Table 5. Data for the Ti-1.5Al-1Fe-7.2Cr alloy (lines 17-19) with somewhat higher chromium content [23,24] were added for comparison to illustrate the influence of C Mo above 10 wt.%. Typical examples of engineering tensile stress-strain curves for alloys #3 and #4 are given in Fig.…”

“…Keeping in mind the differences in chemical composition (Table 3) and lattice parameter c of the secondary α II -phase in the alloy #4 (Fig. 5), in this sense, chromium seems to be a more preferable element, which has a slightly lower diffusion mobility and is not prone to local fluctuations; due to this, the ratio between iron and chromium was shifted toward the latter element, when creating a new metastable β-alloys of the Ti-Fe-Cr-(Al) system [11,12,23].…”

Microstructure and Mechanical Properties of a New Ti–1.5Al–1Fe–7.2Cr Alloy Produced with Conventional Cast and Wrought Approach

“…Therefore, even this as-cast state could be employed for further study regarding the influence of isothermal exposure on the aging behaviour. However, taking into account previous data obtained with a similar composition alloy obtained by the elemental powder metallurgy approach [10], and keeping in mind the aim to eliminate the possible influence of structural and chemical inhomogeneity of the initial cast state, water quenching was applied after exposure at 1173 K for 3.6 ks (single-phase β-field) to form and retain a uniform single-phase metastable β-state. The water quenched specimens were then subjected to isothermal exposure for various durations at two temperatures of 673 and 773 K to study the aging behaviour.…”

“…Another successful approach has been to produce low-cost Ti-Al-Fe-Cr alloys containing high amounts of relatively cheap Fe and Cr [8,9]; however, all developed compositions to date have corresponded to the higher-alloyed metastable β-alloy type. In our previous work [10], where an elemental powder metallurgy approach was employed, we showed that the composition of an alloy of this type can be changed to a lower content of β-stabilizing elements, such as iron and chromium, to 1 and 7% mass, respectively, which corresponds to a molybdenum equivalent of C Mo = 11.5% mass. Such a reduction in the content of β-stabilizing elements allows both a reduction in the cost and specific weight of the alloy, in addition to simplification of the smelting process (due to faster melt homogenization) and shortening of the isothermal exposure during heat treatments due to the high diffusibility of Cr and especially Fe.…”