Enhanced mechanical properties of orthorhombic Ti2AlNb-based intermetallic alloy

Abstract

Attempts were made to improve the mechanical properties of an orthorhombic Ti 2 AlNb-based Ti-22Al-27Nb intermetallic alloy through microstructural and compositional modifications, and the dispersion of fine TiB particulates. A Ti-22Al-27Nb alloy with a prior B2 grain size ranging from 8 μm to 49 μm was successfully obtained using spherical α 2 particles as obstacles to grain growth. The finest grained material showed an excellent combination of room temperature tensile strength (around 1,000 MPa) and tensile ductility (more than 15 %). Transition metal elements such as Mo, V and W for a portion of the Nb in the Ti-22Al-27Nb were substituted. The guideline for this compositional modification required that the beta phase stability in the modified alloy be equal to that of the Ti-22Al-27Nb. It was found that the substitution of 2 % W for 7 % Nb was quite effective in increasing tensile strength at temperatures above 923 K and reducing the steady state creep rate and primary creep strain. The Ti-22Al-27Nb alloy-based particulate composites reinforced with 6.5 % TiB were successfully produced with the gas atomization P/M method. The dispersion of extremely small TiB was very uniform. Most of the mechanical properties of the composites, including the yield stress, tensile strength, Young's modulus, resistance to creep, and high cycle fatigue strength were greatly superior to those of the matrix alloy.

Microstructure, Tensile, and Creep Behaviors of Ti-22Al-25Nb (at.%) Orthorhombic Alloy with Equiaxed Microstructure

“…There are longer slip lines in the equiaxed α 2 phase—this means that plane slippage characteristics were present in the α 2 phase. B2 phase has more slip planes than the α 2 /O phase, thus, deformation was mainly focused in the B2 matrix [ 19 , 20 ]. To further explore the RT deformation mechanism of HT-760, the microstructures were studied by TEM.…”

Microstructure, Tensile, and Creep Behavior of Boron-Modified Ti-15Al-33Nb (at.%)

“…[12,14] Relatively few studies have focused on investigating the effects of B additions on the microstructure and mechanical properties of Ti-Al-Nb alloys. [6,[15][16][17][18][19][20] Emura et al [19] have observed improved tensile strength because of B addition in a Ti-22Al-27Nb (at. pct)/ 6.5 mass pct TiB material.…”

Microstructural Adjustments and Tensile Properties of a Hot-Forged Ti−22Al−23Nb−3V−Y Alloy

“…For the Ti-22Al-26Nb alloy, the addition of 5 at% boron proved to be detrimental to the tensile and creep behaviour 13,14 . The substitution of 2 % W for 7 % Nb in Ti-22Al-27Nb was quite effective in increasing tensile strength at temperatures above 923 K and in reducing the steady state creep rate and primary creep strain 12,15 . The microstructure was sensitive to the cooling rate, through 1130 °C/1h/CC(3 °C/ min and 30 °C/min) + 850 °C/33h/WQ, the structure of Ti-22Al-20Nb-2W consisted of B2 + O, while reducing the cooling rate to 0.3 °C/min, phase compositions were B2 + O + α 2 , 19% of which was α 2…”