Deformation Behavior Of Aluminum Research Articles

Mechanical characteristics and deformation behavior of Al polycrystal reinforced with SiC particles

Molecular dynamics models are established to investigate the influence of silicon carbide (SiC) particle size and strain rate on the mechanical characteristics and deformation behavior of aluminum (Al)/SiC composite. The results show that the ultimate strength of the Al/SiC composite increases from 0.788 to 0.910 GPa as the SiC reinforcement particle size increases from 10 to 30 Å, due to load transfer effects and barriers to dislocation motion. Plastic deformation of Al/SiC composite decreases with increasing SiC particle size, manifested by a lower proportion of atoms subjected to high shear strain for larger SiC particles. The SiC particle size also influences the change in crystal structure during deformation, as shown by the larger particles better supporting the Al matrix in minimizing the dislocation movement. The study shows that the grain boundary and Al/SiC interface play a significant role in the mechanical properties of the composite by impeding the evolution of dislocation and stacking fault. Moreover, the higher strain rates lead to increased ultimate strength and flow stress due to a greater rate of deformation and energy storage. The distribution of shear strain in the composite shows concentrated deformation at the grain boundary, and the large shear-strain region decreases as the strain rate increases. Additionally, higher strain rate leads to more formation of hexagonal-close-packed and amorphous structures, increased dislocation density, and material failure.

Influence of Al3Ni crystallisation origin particles on hot deformation behaviour of aluminium based alloys

Binary Al–Ni, Al–Mg and ternary Al–Mg–Ni alloys containing various dispersions and volume fraction of second-phase particles of crystallisation origin were compressed in a temperature range of 200–500 °C and at strain rates of 0.1, 1, 10, 30 s−1 using the Gleeble 3800 thermomechanical simulator. Verification of axisymmetric compression tests was made by finite-element modelling. Constitutive models of hot deformation were constructed and effective activation energy of hot deformation was determined. It was found that the flow stress is lowered by decreasing the Al3Ni particle size in case of a low 0.03 volume fraction of particles in binary Al–Ni alloys. Intensive softening at large strains was achieved in the alloy with a 0.1 volume fraction of fine Al3Ni particles. Microstructure investigations confirmed that softening is a result of the dynamic restoration processes which were accelerated by fine particles. In contrast, the size of the particles had no influence on the flow stress of ternary Al–Mg–Ni alloy due to significant work hardening of the aluminium solid solution. Atoms of Mg in the aluminium solid solution significantly affect the deformation process and lead to the growth of the effective activation energy from 130–150 kJ/mol in the binary Al–Ni alloys to 170–190 kJ/mol in the ternary Al–Mg–Ni alloy.

ポーラスアルミニウム充填パイプへのスリット導入による変形制御の検討

ポーラスアルミニウム充填パイプへのスリット導入による変形制御の検討

Deformation behaviour of aluminium during machining: Modelling by Eulerian and smoothed-particle hydrodynamics methods

Large-strain deformation behaviour of aluminium that accompanies continuous chip formation during machining (1100 Al) has been studied using experimental and numerical techniques. In experimental studies, local values of plastic strains were determined in the primary and the secondary deformation zones of machined 1100 Al. This was completed through a careful examination of metallographic sections taken from the material ahead of the tool tip, in which orientation changes in the flow lines in the material and shear angles were used to calculate plastic strains. Variations in local flow stresses were estimated from microhardness measurements. The examination of the stresses and strains at each measurement location generated a stress—strain relationship for the 1100 Al material. An important observation from the experimental portion of this research indicated that the material stress—strain response was independent of the feed rates considered in this study. Additionally, the response was observed to obey an exponential relationship with stress saturation occurring at approximately 300 MPa. Parameters associated with the Johnson—Cook constitutive equation were also determined from the experimental work. An Eulerian finite-element method and a relatively new so-called mesh-free method [smoothed-particle hydrodynamics (SPH) method] have been applied to the simulation of machining. The application of these methods permits simulation of the machining process without use of any mesh separation criterion. Appropriate values of the coefficients of friction, for numerical studies, were determined in parametric studies by correlating the experimentally measured chip thicknesses with the numerically predicted values. The effectiveness of the Eulerian and SPH methods in predicting the response of 1100 Al during orthogonal machining has been assessed through a rigorous comparison of the stress—strain distribution within formed chips during steady-state cutting. Both the Eulerian and SPH models showed good overall correlation with the experimentally measured stress—strain distribution when the exponential type material behaviour was assumed in modelling. A maximum stress of 300 MPa at the tool tip was obtained from the numerical simulations using the assumed exponential material behaviour. The location of maximum stress corresponded to the position of maximum strain (8.0). The application of the Johnson—Cook type constitutive equation resulted in predicting a lower maximum equivalent strain (4.5) and higher maximum stresses (325 MPa).

Effect of geometric work-hardening and matrix work-hardening on workability and densification of aluminium–3.5% alumina composite during cold upsetting

The densification is a measure of deformation in upset forming of Powder Metallurgy (P/M) processes. A complete experimental investigation on the deformation behaviour of aluminium–3.5% alumina powder composite has been discussed for the case of triaxial stress state condition. Cold upsetting of aluminium–3.5% alumina composite with and with no annealing having different initial preform relative density and with different aspect ratio was carried out and the densification behaviour of the preform under triaxial stress state condition was determined. A new true strain considering the effect of bulging was taken into account for the case of determination of the hoop strain. Plots made for different preforms were analyzed for the densification behaviour of preforms considering the effect of both geometrical work-hardening (GWH) and the matrix work-hardening (MWH).