Hot working of aluminum alloy 7075
Large deformation, constant true strain rate, isothermal compression tests have been conducted on the aluminum alloy 7075 at strain rates which ranged from 103 to 1 sec1 and temperatures which spanned the practical forging temperature range of 3250C 4250 C. In this strain rate and temperature regime the stress-strain curves show very little strain hardening or softening, and the relationship between the (visco) plastic strain rate iP, the absolute temperature T, and the flow stress a can be represented well by the classical one-dimensional equation:
Additive Friction Stir-Enabled Solid-State Additive Manufacturing for the Repair of 7075 Aluminum Alloy
The repair of high strength, high performance 7075 aluminum alloy is essential for a broad range of aerospace and defense applications. However, it is challenging to implement it using traditional fusion welding-based approaches, owing to hot cracking and void formation during solidification. Here, the use of an emerging solid-state additive manufacturing technology, additive friction stir deposition, is explored for the repair of volume damages such as through -holes and grooves in 7075 aluminum alloy. Three repair experiments have been conducted: double through-hole filling, single through-hole filling, and long, wide-groove filling. In all experiments, additive friction stir deposition proves to be effective at filling the entire volume. Additionally, sufficient mixing between the deposited material and the side wall of the feature is always observed in the upper portions of the repair. Poor mixing and inadequate repair quality have been observed in deeper portions of the filling in some scenarios. Based on these observations, the advantages and disadvantages of using additive friction stir deposition for repairing volume damages are discussed. High quality and highly flexible repairs are expected with systematic optimization work on process control and repair strategy development in the future.
The effect of coulomb friction in the planestrain compression of a plastic-rigid material
Abstract The plane-strain compression of a plastic-rigid material is analysed on the assumption that the frictional conditions between the platens and the material aie such that the shear stress is the same fraction of the normal stress everywhere on the platen surface,unless this value attains the yield shear stress of the metal, which it can never exceed. This is the condition known as Coulomb friction, the ratio being defined as the coefficient of friction μ. The solution has been determined by a geometrical method recently proposed by Prager (1958) for integral ratios of platen breadth/material thickness of 7 and 3, and for values of the coefficient of friction of 0.05, 0.1, 0.15, 0.225, 0.8 and the limiting value of 1 1+ 1 2 π , above which value the yield shear stress is always attained along the complete zone of contact. Comparison is made with an approximate theory in which the state of stress is assumed constant across any section. A simple test is described by means of which the coefficient of friction for material being deformed under plane strain conditions may be determined.