Microhardness Of Alloy Research Articles

The effect of particle content and sintering time on the properties of Al-Al9Co2-Al13Co4 composites, made by powder metallurgy

In the current study, aluminum matrix composites made of Al-Al9Co2-Al13Co4 are developed using powder metallurgy with a flow of N2 at a temperature of 600 °C. In this study, the impacts of process variables such cobalt concentration (0.5, 1, 3, and 5 %at.) and sintering time (4, 8, 24, 48, and 72 h) on hardness were examined. X-ray diffraction analysis, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were used to evaluate the crystalline phase and microstructure of the composites made using the powder metallurgy process. A micro Vickers hardness tester was used to test the mechanical properties. During heat treatment, mixed products Al13Co4 and Al9Co2 were generated in the aluminium matrix through reactive diffusion in solid state. The results show, on the one hand, that the obtained alloys have microhardness values that are significantly higher than those of pure aluminum (49 ± 4 HV). In contrast, the microhardness of alloys based on the compositions ‘Al-0.5%Co’ and ‘Al-1%Co’ increases with the sintering time and achieves a maximum value of 153.89 ± 4.85 HV and 141.49 ± 7.81 HV, respectively, at a sintering time of 72 h. Nevertheless, the microhardness decreases with longer sintering times of 72 h for the higher compositions that were studied ‘Al-3%Co’ et ‘Al-5%Co’. After 48 h of sintering, the microhardness of the ‘Al-3%Co’ alloy falls from 131.88 ± 2.50 HV to 102.67 ± 4.33 HV. For the alloy ‘Al-5%Co’, it decreases from 93.87 ± 2.50 HV to 64.65 ± 2.50 HV after 24 h of sintering. This decrease in hardness is explained by the generation of a large amount of pores during the sintering of the alloys with large compositions.

Структура и механические свойства алюминиевого сплава АК12Д, подвергнутого обработке трением с перемешиванием

The application of friction stir processing (FSP) to modify the structure of the Al–Si alloys, in particular the fragmentation of large silicon particles, can lead to an increase in the level of mechanical properties. This work is aimed to study features of local surface hardening of AK12D aluminum alloy (Al–Si–Cu–Ni–Mg system) during FSP and subsequent T6 hardening heat treatment. The authors investigated the influence of FSP and subsequent heat treatment parameters on the structure, microhardness, and hardness of the AK12D alloy. FSP was carried out at speeds of processing tool rotation and traverse of 2000 rpm and 8, 16 mm/min, respectively. The subsequent hardening T6 heat treatment was carried out according to the standard regime for the AK12D alloy. The paper shows that the FSP mode at a rotation speed of 2000 rpm and a traverse speed of 8 mm/min contributed to the formation of a monolithic and defect-free treatment zone. The study revealed that the formed microstructure is heterogeneous due to the influence of various thermomechanical effects. The most intense structural changes occurred in the stir zone. Friction stir processing and subsequent heat treatment led to fragmentation and partial dissolution of intermetallide particles in the α-Al solid solution followed by its decomposition and formation of secondary hardening phases. Moreover, the FSP and T6 heat treatment led to the formation of quasi-equiaxed fine-grained structure. The AK12D alloy microhardness after treatment under the study varied nonmonotonically and depended on the structure in different zones. At the same time, the Brinell hardness values after FSP and subsequent T6 heat treatment increased compared to the initial heat-treated state.

Study on microstructure and tribological behavior of the selective laser melted MgZnCa alloy

In the current work, MgZnCa alloy was fabricated via selective laser melting (SLM) technology. Microstructural evolution and wear performance of the SLM MgZnCa samples were studied. Tribological behavior of the SLM MgZnCa alloy in a 3.5 wt% NaCl solution was explored. Fine equiaxed grains can be detected both in the XY plane and XZ plane within the SLM samples. Average microhardness of MgZnCa alloy can be enhanced from 65.4 ± 2.04HV0.05 (MgZnCa powder) to 70.6 ± 2.72HV0.05 (SLM MgZnCa samples) owing to the ultra-high cooling rate of SLM process. For tribological behavior of the SLM MgZnCa alloy, adhesive and oxidation wear are the wear mechanisms for the dry friction; while corrosive and adhesive wear are the dominant wear mechanism for the wet friction. Correspondingly, average wear rate of the wet friction [24.21 ± 3.28 × 10−3 mm3/(N∙m)] is 232.10% larger than that of the dry friction [7.29 ± 0.58 × 10−3 mm3/(N∙m)].

Strength, plasticity, microhardness and inhomogeneous plastic deformation of strips made of amorphous multicomponent iron-based alloys

The structure of rapidly quenched ribbons from multicomponent iron-based alloys Fe81.4-Cr4.0-Mo6.0-Ni5.2-C1.0-Mn2.1-Al0.3, Fe71.7-Ni6.0-Co2.4-Cr7.5-Mo7.9-B4.0-Si0.5, Fe86-P9.8-C1.0-Si0.9-Al1.7-B0.6 has been studied by the methods of X-ray diffraction, X-ray phase and micro-Rhspectral analysis, and electron microscopy. It is shown that these materials are X-ray amorphous, and chemical elements are evenly distributed in them. Some physical and mechanical properties (strength, plasticity, microhardness) of amorphous multicomponent iron-based alloys have been experimentally investigated. It is shown that the alloy Fe81.4-Cr4.0-Mo6.0-Ni5.2-C1.0-Mn2.1-Al0.3; has the highest ductility; the highest strength and microhardness is the Fe71.7-Ni6.0-Co2.4-Cr7.5-Mo7.9-B4.0-Si0.5 alloy. Alloy Fe86-P9.8-C1.0-Si0.9-Al1.7-B0.6 is the most fragile, soft and fragile. It was found that the Fe81.4-Cr4.0-Mo6.0-Ni5.2-C1.0-Mn2.1-Al0.3 alloy has the highest inhomogeneous plasticity upon indentation of the surface by the Vickers pyramid. The features and regularities of inhomogeneous plastic deformation of multicomponent amorphous alloys based on iron at room temperature have been studied by the method of surface indentation. It is shown that two types of shear bands are formed at the indentation of the indenter on the surface of the amorphous ribbon: in the form of rays coming from the indentation, and in the form of rings bordering the indentation of the indenter. Under a load on the indenter of 1 N, the shear bands in the form of rays in the Fe71.7-Ni6.0-Co2.4-Cr7.5-Mo7.9-B4.0-Si0.5 alloy have the longest length, and shear bands in the form of rings in the Fe81.4-Cr4.0-Mo6.0-Ni5.2-C1.0-Mn2.1-Al0.3 alloy.

Effect of Flap Peening Speed on the Surface Quality and Micro Hardness of Aircraft Aluminum Alloys

Effect of Flap Peening Speed on the Surface Quality and Micro Hardness of Aircraft Aluminum Alloys

STUDY OF THE CU3AS4TE9-CRASTE3 SECTION OF THE AS2Te3-Cr2Te3-CuTe quasi-ternary system

Chemical interactions in the system were studied by methods of physicochemical analysis (DTA, XRD, MSA, determination of density and microhardness) and its phase diagram was constructed. It was found that the phase diagram of the system is a non-quasi-binary section of the quasi-ternary system As2Te3-Cr2Te3-CuTe. At room temperature in the system of solid solutions based on Cu3As4Te9 reaches - 5 mol. % CrAsTe3. The region of the solid solution based on the CrAsTe3 compound has not been established in practice. The dependence of the microhardness and density of alloys of the Cu3As4Te9-CrAsTe3 system on the composition has been investigated.

Fabrication and characterization of AZ31-B4C composites

In the present study, Magnesium Alloy (AZ31) and AZ31-B4C composites reinforced with the varying amount (0–2 wt%) of nano-sized B4C in particulate form are fabricated through an Ultrasonic stir casting process. The mechanical properties and microstructure characterization are mainly investigated. The microstructural characterization is done through an optical microscope (OM) and scanning electron microscope (SEM) to examine the dispersion and homogeneity of B4C particulates in the Magnesium matrix. Elemental analysis is carried using an energy dispersive X-ray Spectrometer (EDAX). EDAX results indicate the presence of different elements such as Mg, B, C, Al, Zn etc. in base alloy and composites. Mechanical properties such as microhardness and density of base alloy and composites are also determined. Hardness and Density are found to increase with the increasing weight percentage of reinforcement. Microstructure examination found equiaxed grains in fabricated Alloy and Nano Composites. The mechanical characterization shows good interfacial bonding between the Mg matrix and B4C reinforcement material.

Effect of Structural and Phase Changes under Relativistic Electron Pulsed Beam Irradiation on the Aluminum Alloys Micro-hardness

The paper studies the distinctive features of micro-hardness value changes in the zone of industrial aluminum alloy 1933 and alloy 1380 irradiated by the relativistic electron beam. The surface layer was modified under the relativistic electron beam injected along with the equal energy parameters. However, we have to claim that some physical and technological properties of the irradiated alloys layer came with some differences. The modified layer micro-hardness increased over 30% in 1933 aluminum alloy and decreased by 10% in 1380 aluminum alloy. The mechanisms affecting the metal material strengthening transformation after a pulsed electron beam application are analyzed. Thus it was established that one of the core impacts to increase the micro-hardness of 1933 aluminum alloy surface layer was fine MgO impurities being absent in the initial alloy and caused by the irradiation, whilst the micro-hardness of the irradiated layer of the 1380 aluminum alloy decreases due to the dissolution during irradiation of the strengthening phases, which were identified in the initial state.

Influence of cerium content on the microstructure and thermal expansion properties of suction cast Al-Cu-Fe alloys.

Low-expansion alloys are of great importance and can be used for the development of new aerospace materials. Herein, we report diverse rare earth quasicrystal alloys fabricated by the vacuum suction casting process. The effects of the addition of cerium (Ce) on the microstructure, thermal expansion properties and microhardness of the Al-Cu-Fe alloy were systematically investigated. This study discovered the tiny Al-Cu-Fe-Ce microstructure. A uniform distribution could be achieved after Ce addition amount is elevated. At the Ce addition amount of 1 at%, the lowest alloy thermal expansion coefficient was obtained. The alloy exhibited the maximum microhardness under these conditions. The microhardness of alloys containing 1 at% of Ce was approximately 2.4 times higher than the microhardness exhibited by alloys devoid of Ce additives. The coefficient of thermal expansion decreases by approximately 20%. The use of the suction casting process and the addition of an appropriate amount of Ce can potentially help design and develop Al-Cu-Fe-Ce alloys.

Investigation of hardness, wear and magnetic properties of NiCoCrFeZrx HEA prepared through mechanical alloying and spark plasma sintering

In this work, the effect of the addition of Zirconium on the microstructure, hardness, wear behavior and magnetic properties of NiCoCrFe High Entropy Alloy (HEA) was investigated. The crystal structures and phase evolution of the alloys were characterized using X-Ray Diffraction (XRD). XRD patterns showed the FCC and BCC solid solutions in both alloy powders. To investigate the effect of Zr element on the wear behavior of NiCoCrFe HEA, the alloys, in the form of powder, were compressed using Spark Plasma Sintering (SPS) process, and then, the pin on disk wear test was applied. The results showed that after SPS, BCC/FCC phases of the NiCoCrFeZrx (x = 0) alloy had converted to single-phase FCC (NiCoCrFeZr0.4); however, the mechanical properties and wear behavior of the alloy improved compared to the NiCoCrFe alloy. The micro-hardness and nano-hardness of NiCoCrFe alloy increased from 682 ± 7 and 672 ± 7 Vickers to 828 ± 10 and 845 ± 10 Vickers, respectively. Moreover, the addition of Zr led to significant increasing in wear resistance and decreasing the coefficient of friction. Results of the scanning electron microscope (SEM) equipped with an XRD energy spectrometer (EDS) illustrated that the presence of Zr led to the conversion of the dominant abrasive mechanism to adhesive mechanism. Eventually, the results of the Vibrating Sample Magnetometer (VSM) indicated that the addition of Zr element led to the tendency of NiCoCrFe alloy to be paramagnetic. In this way, the magnetic saturation is reduced by 15%, and the coercive force is increased by 133%.

Laser Butt Welding of Thin Ti6Al4V Sheets: Effects of Welding Parameters

Titanium and its alloys, particularly Ti6Al4V, which is widely utilized in the marine and aerospace industries, have played a vital role in different manufacturing industries. An efficient and cost-effective way of joining this metal is by laser welding. The effect of laser power and welding speed on the tensile, microhardness, and microstructure of Ti6Al4V alloy is investigated in this paper. Results show that the microhardness is highest at the fusion zone and reduces towards the base metal. The microstructure at the fusion zone shows a transformed needle-like lamellar α phase, with a martensitic α’ phase observed within the heat affected zone. Results of tensile tests show an improved tensile strength compared to the base metal.

Effect of Mo content on Ti-Al-Mo ternary alloys for biomedical applications

The microstructure, microhardness, nano hardness, wear-resistance, and anti-wear properties of Ti6AlxMo ternary alloys (x = 3–15 wt%) have been studied for biomedical applications. The microstructural and phase analysis have demonstrated that there is an increase in the β phase with the increase in Mo wt%, while α and α2 phases decrease. Consequently, Ti6Al15Mo alloy has the lowest elastic modulus value. The highest micro and nano hardness values were exhibited by Ti6Al6Mo alloy owing to the presence of alpha and beta colonies with low interlayer distance in the microstructure. The hardness and wear resistance properties of Ti6Al15Mo alloys were comparatively higher than existing biomaterials like Ti6Al4V and CP Ti. The Ti6Al15Mo alloy can be considered as a promising new age biomaterial.

Influence of B contents on the microstructure, fracture toughness and oxidation resistance of Mo-Si-B alloys

The Mo-10Si-(0, 5, 10, 15)B (at.%) alloys located in Moss (Mo solid solution) +Mo3Si +T2 (Mo5SiB2) region were prepared by arc melting. The effect of B content on the microstructure, microhardness, fracture toughness and oxidation resistance of the alloys was studied. In the Mo-10Si alloy, there are primary Moss and peritectic Mo3Si phases. With the addition of B, (Moss + T2) binary and (Moss + T2 + Mo3Si) ternary eutectics emerge in Mo-10Si-(5, 10)B alloys. For Mo-10Si-15B alloy, primary Moss disappears and the microstructure is only composed of binary and ternary eutectics. With the increase of B content, the proportion and grain size of Moss decrease. The microhardness of alloys increases with the increase of B content due to the increasing intermetallics. The fracture toughness of alloys decreases obviously in single-edge notched three-point bending testing (SENB) and the fracture mode transforms from transgranular fracture to intergranular fracture because of the refinement of Moss. In the high-temperature oxidation test at 1250 °C, the oxidation weight loss of the alloys decreases with the addition of B due to the densification of the borosilicate layer.

Effect of Al content on the microstructure and mechanical properties of γ-TiAl alloy fabricated by twin-wire plasma arc additive manufacturing system

TiAl alloys are considered as promising high temperature structural materials. However, the inherent brittleness makes it difficult to be processed. In the present research, TiAl alloys with different Al content are fabricated successfully using an innovative twin-wire plasma arc additive manufacturing system. The effect of Al level on the phase composition, microstructure characteristics, microhardness and tensile properties of as-deposited TiAl alloy is investigated in detail. The results show that the α2 phase content exhibits increase tendency with the decrease of Al level, and the α2 phase content is higher in the top region than that in the middle region. The tetragonal ratio c/a of γ phase tends to reduce with the decrease of Al content. The microstructure characteristics also present obvious difference for as-deposited TiAl alloys. The lamellar spacing gradually decreases with the decrease of Al concentration. With decreasing Al level, the microhardness of alloy tends to increase. In addition, the as-deposited Ti-48 Al (at.%) alloy exhibits much better tensile properties than other TiAl alloys due to optimum microstructure characteristics. The findings provide a valuable reference for additively manufactured TiAl alloy with proper composition ratio.

Microstructure and properties of a Ti doped Fe-based SMA coating produced by laser cladding

To improve the microhardness and wear resistance of Fe-based shape memory alloy (SMA), a Ti doped Fe-based SMA coating was prepared on 304 stainless steel by laser cladding. The phase transition temperature, microstructure, phase composition, microhardness, wear and corrosion resistance of the coating were investigated by differential scanning calorimeter, scanning electron microscopy, X-ray diffractometer, microhardness tester, friction tester and electrochemical workstation respectively. The ε → γ phase transition temperature As and Af of the composite coating are 467 and 475 °C, respectively. Furthermore, it has a shape recovery rate of 30.98% at a deformation of 8.4%. The coating has stress self-accommodation characteristics and shape memory effect. There are TiC, γ-austenite and ε martensite phase in the SMA + Ti coating. The average microhardness of the SMA + Ti coating is 1/3 higher than that of the SMA coating, and up to 1/2 compared to the substrate. The friction coefficient of the SMA + Ti coating is 1/3 smaller than that of the SMA coating, and 1/2 compared to the substrate. Corrosion resistance of the SMA + Ti coating has been improved.

Laser shock peening regulating aluminum alloy surface residual stresses for enhancing the mechanical properties: Roles of shock number and energy

The enhancement of the mechanical performance of materials is a continuous pursuit in engineering. Laser shock peening (LSP) is an advanced manufacturing method employing extreme conditions, which effectively improves the mechanical properties of the material surface. Herein, LSP was used to treat aircraft 5A06 aluminum alloy, leading to significant enhancement of properties. In the LSP process, the pulse shock wave caused severe plastic deformation of the metal surface, where the strain rate reached 107 s−1. The dislocations multiplied in large numbers and then evolved into large-angle grain boundaries and other structures to achieve grain refinement. Also, LSP significantly improved the residual stress of metals, causing a series of mechanical improvement effects. Under the impact of fine-grain strengthening, the resultant 5A06 aluminum alloy's micro-hardness was increased to 140 HV, a value 65% higher than that of bare aluminum. After the LSP process, the maximum plastic deformation layer depth (PDLD) reached 800 μm. On this basis, the ultimate tensile strength of aluminum alloy was increased by 27%, and the ultimate tensile displacement was also increased. The LSP treatment increased the strength of aluminum alloy without losing ductility. The resultant sample's friction coefficient was reduced by 34%, and the overall surface-displayed uniform wear. This work reveals the structure-activity relationships between the surface residual stress and metal mechanical properties and clarifies the LSP process's strengthening mechanism.

Influence of copper addition on the properties of equiatomic NiTi shape memory alloy prepared by vacuum induction melting method

In this study the effect of Cu addition on the phase transformation behavior, microstructure, and micro hardness of equiatomic Ni-Ti shape memory alloy was investigated. NiTiCu SMA prepared with the composition (52.119 % at. Ni, 41.731% at. Ti and Cu 6.15 % at.) and compared with the properties of the equiatomic NiTi SMA with composition (50% at. Ni, 50% at. Ti). Vacuum induction melting method used in the preparation of Both SMAs. The Differential Scanning Calorimetry, Scanning Electron Microscope, X-ray Diffraction Analysis, optical microscope and vicker’s microhardness test was used to investigate the characteristics of the equiatomic NiTi and NiTiCu SMAs. The results revealed that when Cu element was added the phase transformation temperatures decreased below body temperature. NiTi matrix phase and Ti2Ni secondary phase exist in both SMA samples, also Cu-rich phase appeared in NiTiCu SMA and this is one of the reasons that lead to increasing the microhardness of alloy when Cu element was added. The value of equiatomic NiTi increases from 238.74 to 329 when Cu element was added (for NiTiCu alloy) after heat treatment.

Influence of hot isostatic pressing on microstructure, properties and deformability of selective laser melting TC4 alloy

The influence of different hot isostatic pressing regimes on microstructure, phase constitution, microhardness, tensile properties and deformability of TC4 alloy fabricated by selective laser melting (SLM) technology was studied. The results show that the microstructure of SLM TC4 alloy is composed of acicular martensite α’ phase, and the sample exhibits high microhardness and strength, but low plasticity. After hot isostatic pressing, acicular martensite α’ phase transforms into α+β phase, and with the increase of hot isostatic pressing temperature and duration, α phase with coarse lath is gradually refined, and the proportion of α phase is gradually reduced. Because of the change of phase constitution in SLM TC4 alloy after hot isostatic pressing, the grain refinement strengthening is weakened, the density of dislocation is reduced, so that both microhardness and tensile strength are decreased by around 20%, the elongation is increased by more than about 70%, even over 100%, compared with as-deposited TC4 alloy. When the hot isostatic pressing regime is 940 °C/3 h/150 MPa, the tensile strength and the elongation achieve optimal match, which are about 890 MPa and around 14.0% in both directions. The fracture mechanism of alloy after 940 °C/3 h/150 MPa HIP is dultile fracture. Hot isostatic pressing causes concave deformation of SLM TC4 alloy thin-walled frames, and the deformation degree increases with the increase of temperature.

Coarsening kinetics of γ′ phase in isothermal aged high Al content Ni–17 at.% Al alloy

The morphology evolution and coarsening kinetics of γ′ phase in high Al content Ni–17 at.% Al alloy aged at 830 °C are studied by transmission electron microscopy (TEM) and hardness analysis. The γ′ phases evolve from the near-cuboidal to rectangular strips along [100] and [010] directions. There is synchronous increase of alloy microhardness and γ′ phase volume fraction in early stage, while the microhardness decreases after 24 h aging with the formation of coalescent γ′ phase. The precipitation process shows the early precipitation stage and the later coarsening stage with the distinct time exponent 0.082 and 0.251 of average particles radius, the strong elastic stain fields make the time exponents of average particles radius lower than 1/3 of Lifshitz-Slyozov-Wagner (LSW) theory. As aging time goes on, the particles size distribution (PSD) is widening, and the peak position moves from 1.0 to 0.9. The relationship between the coarsened γ′ phase and the alloy mechanical property is also revealed in this γ′ phase strengthened high Al content alloy.

Comparison of cryogenic cooling strategy effects on machinability of milling nickel-based alloy

Liquid nitrogen (LN 2 ) cooling can play a green manufacturing role for nickel-based alloy materials, and it is credible for industrial applications and being popularized. A predict model of LN 2 consumption was established considering cooling effect. Meanwhile, a series of processing tests were executed including in flood, LN 2 external spray and LN 2 inner injection cooling strategies. The different cooling effects on the machining accuracy, required LN 2 flow and tool wear were investigated for 3 cooling strategies in detail. The results show that the cutting temperature is more than 400℃for flood cooling, but it is less than 0℃ for LN 2 ones at high speed. Moreover, the inner injection strategy can economize more LN 2 consumption compared with external spay one. When the cutting zone is required lower cooling temperature, LN 2 consumption of inner injection is less half than that of external one. Besides, the tool durability and workpiece processing performances of LN 2 cooling are all increased than flood one. In contrast to flood cooling, the tool life based on LN 2 cooling can be improved about 1 time. In addition, compared with LN 2 external spray, the inner injection cooling has more than 5 min extension at high speed as well as 10 min at low speed. Furthermore, LN 2 inner injection has also a weaker impact on the alloy microhardness and cutting force. Therefore, the study can confirm that LN 2 inner injection cooling strategy is advantageous compared with external spray for LN 2 cooling application.