Formation of TiAl intermetallics by heat treatment of cold-sprayed precursor deposits

Fabrication of TiAl alloys by MA-PDS process and the mechanical properties

A novel reformulation of the Theory of Critical Distances to design notched metals against dynamic loading

The evaporation of fluorine containing gases from metallurgical operations is a significant issue in the industrial use of slags. Experimental studies, undertaken to measure the evaporation rate of fluorine containing gases from liquid slags and from some industrial mold slags in both dry and humid atmospheres, have shown that fluorine evaporation rates were found to be significant in all conditions but were highest under humid conditions.

Fluoride Evaporation from CaF2-SiO2-CaO Slags and Mold Fluxes in Dry and Humid Atmospheres

Investigations are made on the effects of strain rates on the tensile behavior and deformation modes of Duplex Ti–465Al–2Nb–2Cr (DP TiAl) at temperatures ranging from room temperature to 840 °C and under strain rates of 0001, 320, 800, and 1350 s−1 The dynamic strength is higher than quasi-static strength but does not change much over the high strain rate range Yield stress anomaly is not found Brittle-to-ductile transition temperature (BDTT) increases with the increased strain rates A Zerilli–Armstrong constitutive model with appropriate coefficients is chosen to describe the high strain rate flowing behavior TEM analysis indicates that both ordinary dislocations and superdislocations are found and dislocation pile-up only appears in samples deformed under quasi-static loadings at elevated temperatures The deformation twins are common in equiaxed grains and the proportion of twinned grains increases with the increased strain rate from 46–72% under quasi-static loadings to 69–95% under high strain rate loadings No deformation twins are found in lamellar colonies

Tensile impact behavior and deformation mechanism of duplex TiAl intermetallics at elevated temperatures

A γ-base TiAl alloy with duplex microstructure of lamellar colonies and equiaxed γ grains was prepared with a reactive sintering method. Tensile tests and fracture toughness tests at loading velocities up to 12 m/s (strain rate for tensile tests up to 3.2×102/s) were carried out. The micro-structure of the alloy before and after tensile deformation was carefully examined with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The fractography of the tensile specimens and fracture toughness specimens was studied. The experimental results demonstrated that the ultimate tensile strength (UTS) and yield strength (YS) increase with increasing strain rate up to 10/s and subsequently level off. The UTS and YS exhibited similar strain rate sensitivity. The strain rate sensitivity exponent at strain rates lower than 10/s is about 1.5×10−2 and at higher strain rates is almost zero. In this study, fracture toughness was found to be less sensitive to the loading velocity, having values of around 25 MPa √m, which is believed to be attributed to the high strain rate experienced at the crack tip. The predominant deformation mechanism for the strain rates used in this study was found to be twinning. However, in the low strain rate range, the dislocation motion mechanism was operative at the initial deformation stage and twinning dominated the later stage of the deformation process. In the high strain rate range, the entire deformation process was dominated by twinning. The interaction between deformation twinning and grain boundaries resulted in intergranular fracture in the γ grains and delamination of α
 2/γ interfaces in the lamellar colonies.

H. Fukumasu

Papers

Tensile properties and fracture toughness of a Ti-45Al-1.6Mn alloy at loading velocities of up to 12 m/s