Papers by Keyword: Dual Alloy

Abstract: The Ti3Al/TC11 dual alloy bar joined by electron beam welding was deformed by near isothermal forging and then processed by gradient heat treatment. Afterwards, the mechanism of interface strengthening has been investigated according to the microstructure evolution and properties. The results show the brittle phases formed in the re-solidification can be broken by near isothermal forging; the lattice distortion energy is increased obviously due to deformation, so the nucleation ratio of recrystallization is improved, which method is fine-crystal strengthening. After the dual alloy deformed by near isothermal forging is further processed by gradient heat treatment, the room temperature tensile strength of the joint is higher than that of the Ti3Al alloy; the high temperature tensile strength of the joint is equal to or higher than that of the TC11 alloy. The reason is that the finer and phases are precipitated from the phase transus microstructure in the welding interface, which produces the effects of fine-crystal strengthening and dispersion strengthening.

Abstract: The influences of different hot working conditions on the microstructures and mechanical properties at weld zone of the Ti3Al/TC4 dual alloy have been investigated. The experimental results show that forging and heat treatment has significant influence on room temperature tensile strength (RTTS for short) of the weld zone. The influence of forging strain and temperature on its elongation at temperature 500°C is also conspicuous. The results of intuitional and variance analysis show that affecting factors of its RTTS are heat treatment, forging strain, forge temperature and condition of billet in sequence. The affecting factors of its room temperature (RT for short) ductility and the tensile strength (TS for short) at temperature 500 °C are forging strain, forge temperature, heat treatment and condition of billet. Good comprehensive properties are obtained under optimal conditions: forging at 1020°C, annealing at 700°C for 12 hours, air cooled, about 40% strain and as-rolled billet. The microstructures of the weld zone worked according as those conditions are uniform and the grain size is also fine.

Abstract: The development of aeroengines with increasing thrust capabilities requires the development of shaft technology to deal with this greater power transmission, whilst still restricting their dimensions and weight. Modern aerospace drive shafts are predominantly of a single-alloy design and significant benefits could be obtained from using a dual alloy shaft, where a high temperature alloy is used at the turbine, i.e. hot, end of the shaft and a high strength alloy is used for the spline end of the shaft, where high strength is required, rather than high temperature performance. Whilst the processes of joining dissimilar materials are widely used the evolution of the joint and its strength characteristics are not fully understood. A program of research has been instigated to lead to an improved understanding of friction welds and their behaviour under monotonic and cyclic loadings with the overall objective to establish confidence in the welding parameters for these material combinations and the associated post-weld heat treatments. This paper presents an overview of the mechanical testing program and the aims of this work, illustrated with some examples from the monotonic and cyclic test work carried out on inertia friction welded dual alloy shaft components.

Abstract: It has been investigated that the influence of processing parameters on mechanical properties of weld zone for Ti-24Al-15Nb-1.5Mo and TC4 dual alloy welded by electron beam in vacuum. The results shows the remarkable influence factors are heat treatment regime and deformation for yield strength of welded dual alloy samples at room temperature tensile test, and the remarkable influence factor is forging temperature for the elongation in tensile test at 500°C. From the combined analysis about other properties at room temperature and 500°C, the microstructure of the weld seam, it can been gotten the optimum parameters of processing dual alloy, i.e. forging at 1020°C, soaking for 12 hour at 700°C, air cooling, about 40% deformation and using billet of rolling state.