Search

Titanium and its alloys are attractive engineering materials used in aerospace, automotive, biomedical, and marine industry because of their outstanding mechanical properties such as high specific strength and physical properties with excellent corrosion resistance and excellent elevated temperature properties. This paper presents a brief review on the The effects of ball-milling time on the microstructure and mechanical properties of the ball-milled powder and sintered compact were investigated. As-milled powders and sintered Ti-Alloys samples were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, laser diffraction particle size analysis, and transmission electron microscopy.

The Magnesium and its alloys are majorly utilized in automotive, aerospace, and biomedical applications because of their extensive properties. The approach for the preparation of the Magnesium materials is done by modern powder metallurgy. This method allows us to study the structural, mechanical, and controlled corrosion resistance. In the present paper, the effect of cold compaction on magnesium AZ31B alloy are studied, were Ultra-Fined Grained (UFG) Magnesium AZ31B alloys of particle size 60 nm were obtained by 8hrs of Ball milling followed by cold compaction at the pressure of 40Mpa at laboratory temperatures. Sintering process for 8hrs were done for cold compacted specimens at temperatures of 425°C,450°C and 475°C in a Horizontal tubular vacuum furnace. Influence of compacting pressure and sintering were investigated for properties of microstructural, mechanical and corrosion resistance. It was observed that, during cold compaction process for Magnesium AZ31B alloys the product grains are distributed uniformly with less pores and particle boundaries. Homogenization were attended by sintering process and Microstructural, Mechanical properties strength, were shown extensive results of hardness and compressive strength of 516Mpa and 123Mpa, as the sintering temperatures were increased from 425°C to 475°C. The lowest corrosion resistance of 0.35 mm.y-1 is obtained for compacted AZ31B alloy as the temperature of sintering temperature raised to 475°C.

This review paper mainly focused on microstructural and mechanical properties ofultrafine grained nanocrystalline (Nc) Magnesium alloy fabricated by Severe Plastic Deformation(SPD) process. The influence of SPD over mechanical, microstructural, physical, optical, and corrosion properties of Nanocrystalline magnesium alloy are detailed and discussed. It has been observed that nanocrystalline (Nc) magnesium materials has shown superior properties over the bonding of grains while during the Extrusion, Annealing, quenching, Normalizing, Spark Plasma Sintering (SPS) processes. The outcome based by many researchers showed that nanocrystalline Magnesium alloy processed by Severe Plastic Deformation (SPD) showed an improved properties over the Hardness, Dislocation density, Compressive, Tensile and texture, and it’s found to be increased up to certain limit beyond that decrease of microstructural stability, micro hardness and dislocation density were seen to be observed. The Microstructural and Mechanical properties are well improved by Spark Plasma Sintering (SPS), Extrusion, Annealing, Equal channel angular pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT) processes. Grain growth Mechanism, Energies Activation during grain growth, Thermal stability, Relative density and stress corrosion rate were observed by previous Researchers during Fractography analysis over several nanocrystalline (Nc) Magnesium alloy specimens.

Al − Cu − Li alloys are extensively used for aerospace applications due to their high specific strength, good damage tolerance and excellent property stability. An increased usage of Al − Cu − Li alloys depends on enhancing their mechanical properties such as strength and ductility. The processing and development of ultrafine-grained (UFG) materials with grain sizes of tens and hundreds of nanometres, among materials scientists, have gained significant importance in recent times due to the superior mechanical properties achievable in these materials due to the grain size effect proposed by the Hall-Petch relationship. These ultrafine-grained materials are usually produced by severe plastic deformation (SPD) techniques such as ECAP, multiple compressions, and high pressure torsion. Although SPD has its own advantages, the main constraints are that it requires a severe plastic strain, which is larger than unity and the length of materials produced are very limited. To develop an improved approach in achieving an excellent combination of high strength and ductility, the Al − Cu − Li plates was heat treated at 525 °C for 18 h and 10 h of cooling, then subjected to rolling at room temperatures to a reduction of 60% & 75%. The microstructure before rolling and after rolling was found and validated. Mechanical properties such as hardness and wear test for before rolling and after rolling were found and validated. Micro structural characteristics were found with the help of optical microscope.

Cryogenic heat treatment process is well known for enhancing the mechanical properties of alloys having considerably low melting points and less weight. This sub-zero treatment process possesses various beneficial effects on the behaviour and the microstructure of the material treated as well. Cryogenic heat treatment is an in-expensive process in comparison with the other heat treatment process undergone to enhance the core properties of the lightweight alloys. Cryogenic heat treatment hence finds the applications in many industries such as automotive, electronics, aerospace and defence. In the proposed review article, the post effects of the cryogenic heat treatment & Ageing on Aluminium 2099 & Aluminium 8090 alloys were discussed. Even though much detailing is remained to be learnt regarding the postal effects of Aluminium alloys undergoing cryogenic heat treatment. The mechanical properties of ultrafine-grained (UFG) Al-Li alloys with post-aging heat treatment have been investigated.

This paper investigates the Microstructural and Mechanical properties of Wollastonite (CaSio3) ceramics incorporated with Titanium oxide (TiO2) and Hydroxyapatite (HA) composites preparation using Spark Plasma Sintering (SPS). And the influence of Sintering on CaSio3with additives at different temperatures ranging from 1150 °C to 1250 °C with heating rate of 100 °C/min holding time of 10 min are reported and discussed. The microstructure of the sintered samples was investigated by SEM microscopy, XRD Diffraction analyses which presented uniform distribution of the additives (TiO2/HA), having a maximum fine grain size of 32 nm. The mechanical tests were performed for hardness which was 67Hv and Compressive strength of 225Mpa were obtained at the sintering temperature 1250 °C. The superior results have been observed at the highest temperature, along with the addition of the additives (TiO2/HA) to the pure wollastonite over the physical and Mechanical properties.

Synthesis and characterization of Al, Al99.5Zr0.5, Al99Zr1 and Al97Zr3 nanostructures developed by high energy ball milling have been carried out in the present study. Mixtures of Aluminium and Zirconium were added to Tungstan carbide vial (Spex Sample Prep) in the desired quantities. The powder mixtures were milled in a Spex 8000 mixer/mill for 500 min to prepare the required nanocrystalline material. Milled powders were compacted in a cylindrical (8 mm dia) tool steel die under an uniaxial applied pressure 99.5 Mpa in a hydraulic pellet press. The compacted milled powders (pellet) were annealed under 2% H2 (bal. Ar) for 1 h at temperatures from 350 to 500 °C and holding at the same temperature for 1 h. The extents of alloying, structural and morphological changes of the nanocrystalline material in the powder form were analyzed and studied using X-ray diffractometer. X-ray diffraction data was analyzed by using X’Pert highscore plus for the calculation of crystallite size and lattice microstrain (%). The Vickers microhardness of all samples was also measured.

A review on Mechanical properties of ultra-fined grained (UFG) Magnesium based alloy using SPD process is presented in this paper. The properties discussed comprise of microstructural, optical, physical and mechanical behaviour of Ultra- fined grained magnesium alloy and effects of grain size, heat treatment, Extrusion and Annealing, quenching, Normalizing process on these properties. The outcome obtained by many Researchers showed that Magnesium alloy processed by Severe Plastic Deformation (SPD) showed a way to improve the mechanical properties, by refining the grains. The Dislocation density, Hardness, Compressive, Tensile and texture were observed to be increased up to certain limit after that loss of microstructure stability, decrease of micro hardness and decrease in dislocation density were observed. The Mechanical properties are well improved by Extrusion, Annealing, ECAP, ARB and HPT processes. Mechanism of Grain growth, Activation energies for grain growth, stress corrosion rate and Thermal stability were observed by previous Researchers during Fractography analysis on several specimens of Ultra-fined grained Magnesium alloy.

In the present study, the influence of cooling rates (low to ultrafast) on diffusion controlled and displacive transformation of Ti-Nb IF and microalloyed steels has been thoroughly investigated. Mechanisms of nucleation and formation of non-equiaxed ferrite morphologies (i.e., acicular ferrite and bainitic ferrite) have been analyzed in details. The continuous cooling transformation behavior has been studied in a thermomechanical simulator (Gleeble 3800) using the cooling rates of 1-150 °C/s. On the basis of the dilatometric analysis of each cooling rate, continuous cooling transformation (CCT) diagrams have been constructed for both the steels to correlate the microstructural features at each cooling rate in different critical zones. In the case of the IF steel, massive ferrite grains along with granular bainite structures have been developed at cooling rates > 120 °C/s. On the other hand, a mixture of lath bainitic and lath martensite structures has been formed at a cooling rate of ~ 80 °C/s in the microalloyed steel. A strong dependence of the cooling rates and C content on the microstructures and mechanical properties has been established. The steel samples that were fast cooled to a mixture of bainite ferrite and martensite showed a significant improvement of impact toughness and hardness (157 J, for IF steel and 174 J for microalloyed steel) as compared to that of the as-received specimens (133 J for IF steel and 116 J for microalloyed steel). Thus, it can be concluded that the hardness and impact toughness properties are correlated well with the microstructural constituents as indicated by the CCT diagram. Transformation mechanisms and kinetics of austenitic transformation to different phase morphologies at various cooling rates have been discussed in details to correlate microstructural evolution and mechanical properties.

An attempt has been made to investigate the high cycles fatigue behavior of the ultrafine grained (UFG) low SFE Cu-Zn and Cu-Al alloys processed through cryorolling/cryoforging followed by short-annealing. The samples (CRed Cu-9.6% Zn, CFed Cu-9.6% Zn & Cu-4.5% Al, and CRed+short-annealed (225 °C) Cu-4.5% Al), which showed better combinations of YS, ductility and fracture toughness, have been selected to investigate their fatigue characteristics. High cycle fatigue strength of the UFG alloys was found to be consistent in accordance with the static mechanical properties of the corresponding sample. For example, the CFed Cu-4.5% Al alloy samples showed superior fatigue strength along with the best combination of YS, ductility and fracture toughness as compared to that of the other samples. The improved fatigue strength of the alloys has been discussed in the light of effect of low SFE, complex and unique microstructural constituents developed by cryodeformation and role of static mechanical properties of the corresponding sample. TEM analysis after fatigue tests and fractography analysis near to fracture zones corroborated well in explaining the improvement of fatigue life of the UFG alloys.

Aim of the present study is to investigate mechanical properties and fracture toughness of low SFE ultrafine grained (UFG) Cu-4.5 wt% 1 Al alloy processed through multiaxial cryoforging followed by short-annealing. The homogenized annealed samples (800 °C, 4 h) were cryoforged for 5, 9 and 11 cycles. The 11-cycles cryoforged sample showed more than 10 times improvement in the yield strength (YS) (818 MPa) as compared to that of the homogenized annealed sample (76 MPa). However, the ductility decreased to 10.1% elonagtion due to suppression of dynamic recovery and recrystallization during cryoforging. Cryoforging followed by short-annealing (225–300 °C for 20 min) was found to enhance the ductility without affecting its YS. Fracture toughness study has been carried out through analysis of apparent fracture toughness ( K Q ) using linear elastic fracture mechanics, equivalent energy fracture toughness ( K ee ) and J -integral values using elastic plastic fracture mechanics from 3-point bend test data. The improvement of the YS with significant ductility as well as fracture toughness is ascribed to the formation of ultrafine grains & rhombic blocks (due to the intersection of nanotwins close to 90°), mutual crossing & misorientation of microshear bands and multisystem deformation twins. The low SFE of the alloy is found to play the pivotal role to develop such microstructural features.

Aim of the present study is to investigate mechanical properties and fracture mechanisms of low stacking fault energy ultrafine grained Cu-9.6 wt% Zn brass processed by multiaxial forging (MAF) at cryogenic temperature. The alloy was developed by metal mold casting followed by homogenized annealing at 800 °C for 4 h before cryoforging. The forging was carried out for 5, 9 and 12 cycles which are equivalent to cumulative strains of 3.0, 5.4 and 7.2, respectively. The brass deformed with a cumulative strain of 7.2 showed more than 9 times improvement in the yield strength (YS=680 MPa) compared to that of the homogenized annealed sample (70 MPa). However, the ductility decreased to a very low range after deforming to 12 cycles because of extreme work hardening at the cryogenic temperature due to suppression of dynamic recovery. Cryoforging followed by short-annealing (225–300 °C for 20 min) was found to be effective to enhance the ductility without much affecting its YS. Formation of ultrafine grains along with nanotwins (confirmed by TEM) results a simultaneous improvement in the YS and ductility in the cryoforged+short-annealed samples. Macroscopic tensile fracture mechanisms and fractography analysis were carried out for the cryoforged and cryoforged+short-annealed samples. The unified tensile fracture criterion (Ellipse criterion) in terms of modification of the stress state in the fracture zone suggested that reduction of necking angle is resulted from the geometrical hardening effect due to the change of stress state. As number of forging cycles increases, which correspondingly increases critical normal stress (σo) and shear stress (τo), the tensile shear fracture angle decreases indicating in the increase of shear mode fracture. This is ascertained to the grain size refinement, which increases the hardness of the material. Fractography analysis also highly corroborated with the analysis of the unified tensile fracture criterion and %elongation. The dimple size as well as %elongation was found to gradually decrease with decrease in the shear fracture angle, which is equivalent to increase in the cumulative strain.

Cu-2% Al and Cu-4.5% Al alloys were developed by metal mould casting followed by homogenization at 800 °C for cryorolling. The homogenized samples were cryorolled (CR) up to the maximum possible reduction in area (~ 75%). Activation energy for recrystallization of the CR samples was estimated by isoconversion methods using differential scanning calorimetry data; whereas, stored strain energy was determined by X-ray diffraction analysis. The activation energy for recrystallization correlated well with the stored energy of the corresponding sample. Microstructural evolution was analyzed by optical and transmission electron microscopy. The CR + annealed (225 °C) sample showed an improved yield strength (YS) of 810 MPa with a reasonable ductility of 5.1%. The YS found to be 10 times higher than that of the cast + homogenized sample (76 MPa). This is attributed to the recovery of low angle grain boundaries, increasing grain boundary spacing, formation of nanotwins and decrease in the dislocation density without any recrystallization. The YS obtained by analytical modeling of the active strengthening mechanisms is highly corroborated with the experimental YS of the annealed sample. The Hall-Petch strengthening and dislocation strengthening found to play the pivotal role in the improvement of mechanical properties.

In the present study, contribution of individual strengthening mechanisms has been analyzed to corroborate the improvement of the mechanical properties of cryorolled brasses of Cu–3.8% Zn and Cu–9.6% 1 Zn compositions. The samples were cryorolled up to the maximum possible reduction in area after homogenized annealing (at 800 °C for 4 h). After the cryodeformation, a remarkable ~ 12 times improvement of yield strength (YS) was observed for both the alloys compared to that of the homogenized samples. The improvement of the YS is found to be much higher compared to that reported in our earlier work [Mater. Des 67 (2015) 637–643], although alloying content is much less in the present study. This is attributed to the change in rolling design, which allowed deformation of the samples under LN 2 during rolling. The short time ageing (20 min, 225–300 °C) followed by cryorolling was found to enhance ductility without affecting the YS significantly. The solid solution strengthening by Zn in Cu leads to the decrease in the stacking fault energy which prevents the dynamic recovery and restricts the process of cross slip. Thereby, it helps to increase twining activity for further deformation. The TEM investigation confirmed that the formation of subgrains and nanotwins is responsible for the simultaneous improvement of strength and ductility. The analysis of different strengthening mechanisms revealed that the grain size refinement played the pivotal role in the improvement of the mechanical properties.

The mechanical properties and microstructural characteristics of ultrafine grained low stacking faulty energy (SFE) brass processed by cryorolling were investigated in the present work. The commercial brass with 18 wt.% Zn was subjected to cryorolling to obtain specimens with different percentage of reduction in area (RA). Short time post-processing annealing was carried out for the specimens with maximum RA (90%) to enhance their ductility. The mechanical properties of all the specimens were assessed by tensile tests and hardness measurements. Microstructural analysis was carried out by optical microscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and electron microscopy (EM). The maximum yield strength (YS) of 600 MPa with 2.1% ductility was obtained for the cryorolled samples with 90% RA. The YS decreased to 452 MPa with a corresponding increase in the ductility (10%) after annealing at 225 °C. The YS of the cryorolled + annealed sample is found to be 465% higher compared to that of the as-received specimens (YS = 80 MPa). Fractography analysis of the 90% rolled specimens showed a brittle fracture; while, presence of dimples marks on the fractured surface of the annealed specimens indicated a ductile failure. The low SFE of the alloy plays a vital role on the deformation mechanisms during cryorolling and simultaneous improvement of the YS and ductility. Hence, improvement in the mechanical properties has been discussed in the light of refinement of microstructure, formation of sub-grains and nano-twins driven by the low SFE.

In the present work , the cast structures of Cu-4.5wt% Al alloy was homogenized by annealing at 800 °C for 4 h. The samples were kept under LN2 before and during the rolling process in each pass to maintain a constant LN2 temperature. Mechanical properties were evaluated by the tensile test. Microstructural analysis was carried by optical microscopy and TEM analysis. The maximum yield strength (YS) of the 75 % cryorolled samples of Cu-4.5wt% Al alloy was found to be 786 MPa with a ductility of 4.8 %. This is due to the formation of ultrafine grains and nano-twins possibly play the pivotal role for the improved YS and ductility.