Akrum Abdul-Latif

Microstructure Analysis of Aluminum Alloy and Copper Alloy Circular Shells After Multiaxial Plastic Buckling

Aluminum and copper cylindrical shells were plastically buckled under quasi-static and dynamic loading conditions with an Absorption Compression-Torsion Plasticity (ACTP: Patent No. WO 2005090822) combined mechanical testing device. Optical microscopy and transmission electron microscopy (TEM) analysis were used to study the microscopic evolutions in the mechanically buckled aluminum and copper alloy samples. Optical microscopy showed evidence of the presence of second-phase particles in both the aluminum and copper alloys samples. Under dynamic loading aluminum samples showed more energy absorption as compared to copper samples. Material flow lines were more pronounced in the copper samples when observed by optical microscopy. The evidence that supports the increased energy absorption in the aluminum cylindrical shells can be supported by the TEM analysis more than the optical microscopy analysis. The TEM results showed highly oriented textured morphology with the presence of few dislocation cells structures and sub-structures.

Microstructure and Mechanical Properties of Commercial Purity HIPed and Crushed Aluminum

Ultrafine-grained aluminum microstructures were processed from commercial purity powder by combining hot isostatic pressing (HIP) and dynamic severe plastic deformation (DSPD). After the first step, the bulk consolidated material showed a random texture and homogeneous microstructure of equiaxed grains with an average size of 2µm. The material was then subsequently impacted, using a falling weight at a strain rate of 300s-1. The resulting material showed a microstructure having an average grain size of about 500 nm with a strong gradient of fiber-like crystallographic texture parallel to the impact direction. The mechanical properties of the impacted material were subsequently characterized under compressive tests at room temperature at a strain rate of 10-4s-1. The effect of the change of the deformation path on the mechanical response parallel (DN) and perpendicular (DT) to the impact direction was also investigated. These results are here discussed in relation with microstructure and texture evolution.

Thermo-Mechanical Description of AISI4140 Steel at Elevated Temperatures

The recently increasing use of the high strength steel alloy AISI4140 in structural and marine applications necessitates the need to understand the micro- and macro-structural behavior of the alloy at different loading conditions. The behavior of most steel changes during deformation and the damage process may start in the form of micro-cracks and micro-voids leading, at its latest stage, to the development of macro-cracks, and consequently, to material failure. This paper presents experimental results of the flow stress, as well as SEM images, to describe the microstructure of the alloy at different levels of strain rates (quasi-static) and temperatures. The main objective is to introduce a systematic understanding of the ductile failure mechanism due to accumulation of plastic deformation to enable proper structural design; and hence provide better serviceability.