The application of magnesium alloys is greatly limited because of their relatively low strength and ductility. An effective way to improve the mechanical properties of magnesium alloy is to refine the grains. As the race for better MATERIALS performance is never ending, attempts to develop viable techniques for microstructure refinement continue. Further refining of grain size requires, however, application of extreme value of plastic deformation on material. In this work, an AZ31 wrought magnesium alloy was processed by employing multipass accumulative back extrusion process. The obtained microstructure, texture, and room temperature compressive properties were characterized and discussed. The results indicated that grains of 80 nm to 1 mm size were formed during accumulative back extrusion, where the mean grain size of the experimental material was reduced by applying successive ABE passes. The fraction of DRX increased and the mean grain size of the ABEed alloy markedly lowered, as subsequent passes were applied. This helped to explain the higher yield stress govern the occurrence of twinning during compressive loading. Compressive yield and maximum compressive strengths were measured to increase by applying successive extrusion passes, while the strain-to-fracture dropped. The evolution of mechanical properties was explained relying on the grain refinement effect as well as texture change.

An ULTRAFINE/nano GRAINED AZ31 magnesium alloy was produced through four-pass ECAP processing. TEM microscopy indicated that recrystallized regions included nano grains of 75 nm. Pole figures showed that a fiber basal texture with two-pole peaks was developed after four passes, where a basal pole peak lies parallel to the extrusion direction (ED) and the other ~20° away from the transverse direction (TD) in the ED– TD plane and 70° from the normal direction (ND ) in the TD– ND plane. The texture of recrystallized grains at the vicinity of grain boundaries was addressed. To investigate the recrystallization texture, the orientation relationships for the recrystallized and parent grains were studied for the material deformed up to first and second passes. The EBSD results implied that the grains recrystallized at the grain boundaries during the first pass, almost follow the orientation of prior deformed grains, while during the second pass the grain boundary recrystallization adopted a texture different from the parent grains. It was rationalized that as the number of passes increased, the grains recrystallized at prior grain boundaries tend to take different orientation to that of deformed grains.

The aim of current research was to examine the texture of annealed Al-7075 alloy that develops during Equalchannel angular pressing (ECAP) in different ECAP routes. After annealing heat treatment, the material was pressed up to 4 passes by route A and BC at room temperature. The effect of copper tube casing on the texture evolution was also investigated. The texture was studied by X-Ray diffractometer in ED-plane as well as TD-plane. The qualitative and quantitative analysis of the texture reveals that the texture of the first pass is relevant to initial texture, but by increasing pass number this dependency disappears and the texture is mainly relevant to processing route. The texture calculation by Labotex software shows that the results in both TD (z) and ED (x) planes are in good agreement and covering the specimens with copper tube causes a decrease in texture strength and microstructure inhomogeneity of the specimens.

The evolution of texture was discussed during the formation of ultra-fine and nano grains in a magnesium alloy severely deformed through accumulative back extrusion (ABE). The microstructure and texture obtained after applying multiple deformation passes at temperatures of 100 and 250°C were characterized. The results showed that after single ABE pass at 100°C an ULTRAFINE/nano GRAINED microstructure was obtained, while the initial texture was completely replaced by a new fiber basal texture, inclined at 40oC to the transverse direction. As the processing temperature increased to 250oC, the obtained texture intensities were strengthened, though the c-axis of crystals gradually rotated towards the transverse direction and a<10-11>fiber texture parallel to normal direction was developed. Moreover, repetitive ABE was associated with the tendency of the basal plane to lie parallel to TD, while the orientation of the prismatic planes showed a random distribution around ND. After eight passes, the most noticeable texture obtained included the fiber basal texture oriented almost parallel to the transverse direction, and<10-10>perpendicular to the ED and<10-11>parallel to the ND. The maximum texture intensity decreased as the number of passes increased, which is attributed to strain path change involved during each consecutive ABE pass, as well as promoted the contribution of non-basal slip systems.

One of the most important factors affecting the mechanical, physical and chemical properties of metals, are crystal structure and grain size. ULTRAFINE metals with an average grain size of 1000-100nm and nanostructured metals have an average grain size of less than 100nm. ULTRAFINE and nanostructured MATERIALS are known as a new generation of metal products, which have remarkably mechanical and physical properties in comparison to coarse-GRAINED metals. In the last two decades, due to good properties such as high strength, high ductility and toughness, good corrosion resistance and high superplasticity properties, these MATERIALS have been considered by many researchers. In recent years, many methods have been proposed for severe plastic deformation and are now being developed and expanded. In these processes, in spite of the high hydrostatic pressure and the unaltered dimensions of the sample during the process, it is possible to apply very high strains, which results in the desired mechanical properties and ULTRAFINE GRAINED and nanostructured MATERIALS. The accumulative roll bonding process is one of the methods of SPD. ARB process is simple, extensive use, low-cost, industrially capability method that can produce ULTRAFINE and nanostructured metals. In this research, light metals such as aluminum, magnesium and titanium and also extremely used metal such as copper and steel are discussed. Also, mechanical properties, fractography and microstructural properties of ULTRAFINE and nanostructured metals produced by ARB are compared with initial samples and the mechanisms governing of ARB process that cause changes in mechanical and microstructural properties are analyzed.

Commercial pure (CP) titanium has many biomedical applications, especially in implants due to its excellent biocompatibility. The major weakness of CP titanium is its low strength compared to the other titanium alloys. One of the methods which can be utilized for enhancement of CP titanium strength is severe plastic deformation methods. Therefore, the aim of this research is to improve the strength of CP titanium by grain refinement through multi directional forging (MDF). For this purpose, after one hour annealing at 800oC, the CP titanium was forged by MDF process up to six passes at ambient temperature. Microstructural analysis was performed by optical microscope and scanning electron microscope equipped with EBSD. Mechanical properties were also studied by Vickers micro hardness and tensile tests. The finite element simulation was also applied to predict the strain distribution during MDF process. The results of microstructural analysis showed that the average grain size decreased significantly after the MDF process and increasing pass numbers led to the refinement of grain size. After six passes of the MDF process, the average grain size decreased from 45 micrometers to 390 nm. Mechanical properties results showed that the strength and hardness of specimens were enhanced with MDF process and increasing the number of passes. The hardness and strength of six passes MDFed specimen was about 2 times greater than those of the annealed one. The strain distribution results obtained from the simulation showed good agreement with experimental results of microhardness distribution.

Additive manufacturing (AM) has emerged as a transformative technology that produces complex, high-performance components, enabling unprecedented design flexibility and material efficiency. This paper explores the potential of additive manufacturing processes to produce ULTRAFINE/nano-GRAINED microstructures, which are characterized by superior mechanical properties, enhanced corrosion resistance, and improved thermal stability. The study delves into various AM techniques based on the physical phenomenon incorporated to additively bond the material portions. Accordingly, the reported results in the literature were reviewed by categorizing the methods into melting-based and deformation-based approaches and examining the conditions and parameters critical to achieving ULTRAFINE/nano-GRAINED microstructures. Key factors, including the optimization of process parameters as well as the specification of initial feedstock material, are discussed. This comprehensive review shows that in melting-based methods, lower power and higher scan speed result in reduced heat input, leading to smaller melt pools and faster solidification rates, which in turn produce finer grains. On the other hand, in deformation-based methods, smaller initial particle sizes and higher particle velocities generate greater impact energy, which can lead to grain size reduction. This review article also highlights the current potential and achievements in the field of additive manufacturing for producing ULTRAFINE/nano-GRAINED MATERIALS, which may contribute to the development of high-performance MATERIALS and components for the next generation.

In this research, a hybrid method of a simple shear extrusion (SSE) process is proposed with simultaneous application of ultrasonic vibrations at the beginning of the deformation zone in pure copper. A cylindrical-conical-cylindrical horn was designed to amplify and transmit the ultrasonic vibrations using modal analysis in Abaqus. The resonant frequency of 20.332 kHz was used with two amplitudes of 15 and 25 micrometers. Then, the produced ultra-fine grain copper samples after the first pass with and without ultrasonic vibrations were compared. A 54% and 65% reduction in grain size were reported in ultrasonic-assisted simple shear extrusion (USSE) with two amplitudes of 15 μm and 25 μm, respectively. Also, a significant increase in microhardness values in the USSE method compared to the SSE method indicated that the hardness increases significantly by increasing the amplitudes under the influence of acoustic hardening. In addition, the required force to extrude the samples with the presence of ultrasound was reduced under the effect of acoustic softening. In addition, finite element simulation of both SSE and USSE processes was performed in Abaqus/Explicit software. Higher equivalent plastic strain and plastic deformation along the length of the sample were reported in the USSE method. Additionally, in the USSE method compared to the SSE method, the maximum plastic strain distribution was improved by applying ultrasonic vibrations.

In this paper, an advanced thermo-mechanical treatment was conducted on AISI 316 austenitic stainless steel. At first, three samples were rolled at the ambient temperature, the temperature of-20 º C (dry ice and ethanol) and-196 º C (liquid nitrogen). Then, the samples were annealed at 800 º C in the time range of 1 to 15 minutes. In each step, the microhardness values of the samples were measured. Microstructural investigations were conducted using optical and SEM microscopes and Clemex software. Results showed that microhardness of the samples increased due to the formation and precipitation of carbides. The formation of martensitic microstructure after the rolling process was revealed by X-ray diffraction analysis; and by decreasing the rolling temperature, the peak intensity increased. Also, by increasing the annealing time in each step, the volume fraction of the reverted austenite and the intensity of the austenite peaks increased.