Effect of Ultrasonic Compound Cutting on the Microstructure and Properties of Formed Chip

Sever plastic deformation (SPD) with high strain rate can increase the material dislocation density, reduce the grain size and improve the mechanical properties. In this paper, ultrasonic compound cutting (UCC) was proposed to improve the efficiency of preparing ultra-fine grained (UFG) pure copper by sever plastic deformation methods. The motion characteristics and strain rate model of UCC were analyzed, and it was concluded that ultrasonic vibration can increase the strain rate in the primary shear zone. According to the 3D FEM equivalent model of UCC, the UCC and traditional compound cutting (TCC) were compared and analyzed from the perspective of strain rate. The simulation results show that ultrasonic vibration can significantly increase the strain rate of chip. The microstructure and mechanical properties of pure copper chip were studied by using a self-developed machining device. The experiment results show that the grain refinement, dislocation density and micro-hardness of pure copper chip were significantly improved in UCC. When the ultrasonic amplitude is 3 µm, the UCC chip grains are about 2.66 µm and the hardness reaches 124 HV, which is about 8% higher than the hardness of TCC chip. The findings of this research provide an important reference for machining UFG pure copper with enhanced mechanical properties.

Analytical modeling of work hardening of duplex steel alloys in milling process

Sever plastic deformation in cutting operations such as milling, might change mechanical properties of the machined surface. This study presents an analytical model to calculate work hardening of the upper layers of the workpiece in the milling process of 2205 duplex stainless steel. In this regards, the stresses in the cutting regions are calculated to find the stress and temperature fields in the workpiece. Then the strain and strain rate values are calculated for each point of the surface and subsurface layers using the determined stress field. Finally, Johnson-Cook material model is used to calculate flow stress and work hardening. Experimental results of the different machining conditions has been used to validating the proposed model, however comparisons of subsurface microhardness obtained by analytical model with experimental tests shown that the model properly predicts the amount of work hardening.

Aluminum Surface Inclusions of Insoluble Lead Enhanced through Mechanical Attrition of Al Substrates

Preparation of aluminum substrates for surface segregation enhancement of insoluble lead deposition was achieved. Sever plastic deformation 'SPD' of Al sheets was done using surface mechanical attrition treatment 'SMAT' in air. Scanning electron microscope SEM of etched Al substrates cuts showed micro-cavities both on the surface and in-depth. Orientation effects and surface inclusions of Pb inside Al surface found at 40 and 50 Hz - SMAT Al by X-Ray diffraction and energy dispersive of X-Rays EDX. Concluding that SMAT frequency limits used enhanced surface inclusions without annealing that could improve adhesion of industrial protective Pb coatings.

Erosion Corrosion Behavior of Nanostructure Commercial Pure Titanium in Simulated Body Fluid

To date, ECAP technique have been successfully employed to produce Ultra-fine/Nanostructure grain materials, but some materials such as hexagonal closed-packed (HCP) alloys are difficult to process by ECAP at room temperature. In this work, Transmission Electron Microscopy (TEM), Vickers hardness test and Torsion test were employed to confirm the attainment of ultrafine/nanostructured grain (UFG/NSG) commercial pure titanium (CP-Ti) Titanium fabricated by ECAP as a sever plastic deformation process. The samples were pressed by ECAP (route BC) up to four passes at elevated temperature (400° C). Finally, the Erosion-Corrosion (E-C) behavior of ultrafine/nanostructured grain (UFG/NSG) Titanium in a simulated body fluid were investigated through weight loss measurement.

Effect of Shot Peening on Microstructure and Properties of 34CrMo4 Alloy

Plastic deformation can induce surface modification, such as shot peening (SP) on workpiece surface is the hot issue of recent scientific research. SP is the efficient way to improve mechanical behavior of specimens by inducing sever plastic deformation on their surface. Nevertheless, this surface treatment induced complex microstructural evolutions such as grain refinement, will enhance the corrosion resistance of specimens. In this work, the microstructure and properties of 34CrMo4 alloy of before and after SP for 20 min have been investigated. The evolution of microstructure and properties were analyzed from the surface and cross-section. The microstructure morphology at the different depth was determined by optical microscope. The results show grain size is increasing with the depth, and the microhardness and compressive residual stress decrease gradually. In terms of corrosion resistance, the 50 μm depth specimen has the best property than other depth, which the potential and corrosion current density are-0.484 V and-5.72 Acm-2, respectively. The maximum polarization resistance is 2055 Ωcm2by capacitive arc radius of electrochemical impedance spectroscopy.

Design Optimization of Angular Extrusion for Severe Plastic Deformation of Tubular Specimens

The purpose of this work is to optimize angular extrusion for sever plastic deformation of tubular specimens. A finite element model (FEM) was built in Deform-3D® for three extrusion dies and analyzed. The dies were ECAP (135°), TCAP with external groove of 90° (denoted as TCAP-e) and TCAP with internal groove of 90° (denoted as TCAP-i). The analysis for process parameters (such as coefficient of friction-μ, die angles-ѱ and φ, temperature - T, and radius ratio-R) showed that TCAP-i was the optimal die in processing Al6063 tubes based on strain and load distribution of the model. The TCAP-i die model was further optimized for different parameters namely die angles, coefficient of friction, deformation ratio and temperature. The results showed that at constant process temperature of 25 °C, the optimal TCAP-i has the following parameters: φ2=800, Ѱ1=300, Ѱ2=800, Ѱ3=300, μ =0.4 and R =1.5.

Microstructural Modification of AZ91 Magnesium Alloy Using Friction Stir Processing and Carbon Fibers

The microstructure of cast magnesium (Mg) alloy, AZ91, was modified by a friction stir process (FSP) technique. FSP was applied to AZ91 plate with a narrow slit, in which carbon fibers (CFs) were filled. The rotating FSP tool consisting of probe and shoulder could modify the microstructure of the material by sever plastic deformation (SPD) and simultaneously disperse CFs into the matrix. Microstructural observation revealed that sever stirring of material by a tool resulted in the grain refinement due to the dynamic recrystallization and distribution of CFs into the stir zone (SZ). The distribution was not uniform depending on the plastic flow in the SZ, but any worm-hole defects were not formed. Hardness of FSPed AZ91 in the SZ was higher than the as-casted AZ91 because of the grain refinement and distribution of hard CFs.

Influence of Sever Plastic Deformation on the Consolidation Behavior of Al-SiC Mixed Powder

Oxidized and non-oxidized SiC particulates were mixed with Al powder respectively and the two kinds of mixed powders were consolidated at 250°C by equal channel angular pressing and torsion (ECAP-T), which belongs to severe plastic deformation. The interfacial bondings of as-consolidated composites were characterized by SEM images, corrosion morphology and fracture morphology. The results show that after severe plastic deformation, the interfacial bonding between non-oxidized SiC and Al is a kind of mechanical bonding and the consolidation is not firm enough so that the composite has a weak corrosion resistance and its tensile sample has a brittle fracture. However, the composite containing oxidized SiC has a dense microstructure, high corrosion resistance, ductile fracture due to the metallurgical interface.