Effect Of Hot Extrusion Research Articles

Effects of hot extrusion on compressive strength and densification of aluminium-based metal matrix composites

ABSTRACT Metal matrix composites (MMC) made from powder metallurgy (PM) require post-processing to improve the mechanical properties or achieve the final shape. In this experimental study, Aluminium metal matrix composite (Al-MMC) was first fabricated through PM, followed by a hot extrusion process to study the effects of extrusion on compressive strength and density. Hot extrusion of Al-MMC results in microstructure refinement, enhanced dispersion of reinforcement particles and improved mechanical properties. The experimental findings revealed that hot extrusion of Al-MMC resulted in densification, reflected as an average improvement of 5% in the density. An average improvement of up to 22% was observed in the compressive strength of the Al-MMC. Therefore, hot extrusion can be considered an effective post-processing method for enhancing the Al-MMC fabricated through PM. It was also found experimentally that the extrusion ratio also affects the mechanical properties and performance of Al-MMC. It was revealed that the compressive strength is enhanced with an increase in extrusion ratio. It is also important to note that the PM process is one of the processes which offers reasonable control over the utilisation of starting material. Hence, reinforcement retention is higher than other methods like stir casting.

Microstructure and Properties of As‐Cast Mg–2.0Sn–1.0Zn–1.0Y–0.3Zr Alloys at Different Extrusion Ratios

Herein, the effect of hot extrusion with different extrusion ratios (λ = 6, 8, 10, and 12) on the microstructure evolution and properties of as‐cast Mg–2.0Sn–1.0Zn–1.0Y–0.3Zr magnesium alloys, using optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion and electrochemical corrosion experiment, and tensile testing, is investigated. The results show that the Mg14SnY and Mg6SnY precipitated phases exist in the alloy before and after extrusion. After hot extrusion, the second phase of the alloy is broken into particles along the extrusion direction, whereas the grain size is significantly reduced, and dynamic recrystallization and deformed grains exist in the microstructure. The mechanical properties of the extruded alloy improve, but the corrosion resistance weakens. When the extrusion ratio is λ = 10, the extruded alloy exhibits relatively good mechanical properties and corrosion resistance. The corrosion behaviors of the extruded alloys are affected by both the grain size and galvanic corrosion. In the initial stage of corrosion, intergranular corrosion plays a major role in reducing the corrosion resistance of the extruded alloys. With prolonged corrosion time, galvanic corrosion has a more significant effect on weakening the corrosion resistance of the extruded alloys.

Tailoring microstructure of a nickel aluminium bronze by hot extrusion and its impact on mechanical and corrosion behaviour

The effect of hot extrusion on microstructural evolution, mechanical properties, corrosion, and erosion-corrosion behaviors of a nickel-aluminium bronze (NAB) alloy (Cu-9Al-4.5Ni-4Fe-1Mn, wt%) was investigated. After hot extrusion, the microstructure was refined and become more homogeneous. In addition, the layered structures were broken and sepheroidized. These microstructural changes lead to improved mechanical behavior (hardness, strength, and elongation) and higher resistance to corrosion/erosion-corrosion. The reduced potential between phases in hot-extruded NAB alloy, the denser and more uniform corrosion layer, and its strong bonding to the substrate, all lead to improved corrosion resistance, especially in flow conditions.

Effects of hot extrusion on the microstructure and mechanical properties of 2024Al-GNPs composites

Effects of hot extrusion on the microstructure and mechanical properties of 2024Al-0.8GNPs (graphene nanoplates) composites were evaluated. Results showed that the microstructure and mechanical properties of 2024Al-0.8GNPs composites gradually improved with increasing extrusion ratio in a given range of extrusion ratios. At an extrusion ratio of 16, the most noticeable improvement in the microstructure and mechanical properties of the composites were obtained. The tensile strength, yield strength, elongation, and microhardness reached 345.8 MPa, 246.7 MPa, 13.5 %, and 181.6 HV, respectively, which were 90.5 %, 91.7 %, 150.0 %, and 95.3 % higher compared to the as-cast matrix alloy. And the composites exhibited typical ductile fracture characteristics. The dual effects of high-energy ultrasound and hot extrusion improved the interface between GNPs and the Al matrix. The effect of good interfacial structure and good dispersion induced the GNPs in composites to effectively exert thermal residual gravitational strengthening, load transfer strengthening, Orowan strengthening, and fine grain strengthening. • The dual effects of high-energy ultrasound and hot extrusion improved the interface between GNPs and the Al matrix. • At an extrusion ratio of 16, the microstructure was effectively improved and there were obvious textures in the <001> and <111> crystal directions. • Under the optimum extrusion ratio, the tensile strength, yield strength, elongation of 2024Al-0.8GNPs composites reached 345.8 MPa, 246.7 MPa and 13.5%, respectively.

The Effects of Thermal Treatment on the Properties and Performance of Hot Extruded Zn-Based Bioresorbable Alloy for Vascular Stenting Applications.

A new series of zinc alloys is in development for bioresorbable stent implantation to alleviate the current materials' long-term complications. Characterization and optimization of the microstructure and corresponding mechanical properties during manufacturing stages will help researchers meet the required values. In this study, the effect of hot extrusion on the Zn-Ag-Mn-Cu-Zr-Ti alloy is characterized. Additionally, thermal treatments at 390 °C for 15, 25, 40, 60, and 120 min were performed to evaluate the effect of intermetallic phase fractions on the corrosion resistance and mechanical strength. Quantitative analysis of X-ray diffraction data demonstrates that the fractions of the MnZn13, ZrZn22, and Zn0.75Ag0.15Mn0.10 intermetallic phases decrease as the thermal treatment time increases. Corrosion tests reveal a reduction in the corrosion rate of the extruded alloy after thermal treatment. The results of uniaxial compression tests and tensile tests show lower strength and higher ductility in all heat-treated conditions compared with the as-extruded condition.

Effect of hot extrusion on the microstructure and mechanical properties of SiCNWs/Mg-2Zn-0.1Y composite

This work investigates the effect of adding SiC nanowires (SiCNWs) on the microstructure and mechanical properties of Mg-2Zn-0.1Y matrix composites under different hot extrusion parameters, and the strengthening mechanism was analyzed. The results showed that as the extrusion temperature elevated from 140 °C to 220 °C or the extrusion speed increased from 0.1 mm/s to 1.0 mm/s, both the dynamic recrystallized grain size and the recrystallized volume fraction increased significantly. The changes of precipitate size and volume fraction exhibited the same trend. The finest recrystallized grains (~0.37 μm) were obtained after extrusion at 140 °C and 0.1 mm/s, which also contained nano-sized MgZn2 precipitates and SiC nanowires. As the extrusion temperature increased from 140 °C to 220 °C at a constant extrusion speed of 0.1 mm/s, the strength of the composites decreased while the elongation improved greatly. Similar change in the strength and elongation were obtained in the composite as the extrusion speed increased from 0.1 mm/s to 1.0 mm/s at extrusion temperature of 140 °C. Meanwhile, these composites exhibited a weakened texture, and a mixture of microcracks and dimples was observed in the fracture surfaces of the as-extruded composites, which explained the mix of brittle-ductile fractures of the composites. The composites extruded at 140 °C and 0.1 mm/s exhibited the best performance with yield strength (YS) and ultimate tensile strength (UTS) of ~495.53 MPa and ~514.18 MPa, respectively. Among all strengthening mechanisms, the proportion of grain refinement strengthening is the highest.

Effect of hot extrusion on AZ91 alloy corrosion behaviour

ABSTRACT The effect of hot extrusion on the corrosion behavior of AZ91 alloy was studied by observing the change of grain size, the size and distribution of precipitated phase on the transverse and longitudinal sections before and after extrusion. The results show that the grain refinement of alloy was significant after extrusion, the grain size of the transverse section was uniform, that of the longitudinal section was different and the parallel streamline of shear stripes appeared. After extrusion, the decrease of the β-Mg17Al12 phase size reduces the relative potential difference between the second phase and the α-Mg matrix; the reduction of the transverse section was particularly significant. Grain refinement and precipitate size reduction after extrusion can improve the corrosion resistance of the AZ91 Mg alloy, which is the reason why the corrosion resistance of the transverse section was better than that of the longitudinal section.

Effect of hot extrusion on microstructure and tribological behavior of Al2O3p reinforced 7075 aluminum-matrix composites

Effect of hot extrusion on microstructure and tribological behavior of Al2O3p reinforced 7075 aluminum-matrix composites

Effect of Hot Extrusion on Microstructure and Mechanical Properties of Mg–5Sn–xZr Alloys

The effects of Zr addition (0, 0.5 and 1 wt%) and extrusion ratio (6:1 and 12:1) on microstructure and mechanical properties of the Mg–5Sn alloy were studied. Results showed that the dendritic structure of the as-cast M–5Sn alloy gradually transformed into a nearly globular structure with Zr addition. The effect of Zr addition was evident through refining the microstructure, promoting the tendency to form partially divorced eutectic and increasing the Mg2Sn volume fraction, which improved the thermal stability of the alloy during homogenizing treatment at high temperatures. Hot extrusion was found to be very effective for enhancing both strength and ductility of the Mg–5Sn–xZr alloys. Grain refinement induced by twin dynamic recrystallization and dynamic precipitation of fine particles were realized as the main strengthening mechanisms of the extruded alloys. It was found that an increase of the extrusion ratio led to relatively coarser grains, lower yield strength, and higher hardening capacities. However, the Mg–5Sn–1Zr alloy extruded with the area-reduction ratio of 12 exhibited the best combination of tensile strength and elongation of 243 MPa and 10.6%, respectively. Moreover, tensile fracture studies revealed the intergranular cracking and quasi-cleavage fracture as the dominant fracture modes of the as-cast and extruded alloys, respectively.

Effect of hot extrusion on mechanical and microstructural characteristics of stir cast AA6061/SiC/graphite hybrid composites

Abstract Hybrid composites find a wide spectrum of applications in commercial aircraft and the automotive industry. In this investigation, the stir casting method was used to fabricate AA6061/SiC/graphite hybrid composites. The fabricated composites were subjected to a hot extrusion process. Hot extrusion studies on stir cast samples were attempted in this investigation. The tensile and hardness properties of both stir cast and extruded samples of AA6061/SiC/graphite hybrid composites were experimentally evaluated. A comparison has been made on the mechanical properties of both stir cast and extruded samples. The microstructural characteristics of stir cast and extruded samples were also analyzed. The hot extruded samples were found to possess higher tensile strength and hardness and better microstructural characteristics compared with stir cast AA6061/SiC/graphite hybrid composites.

Effect of Hot Extrusion on Microstructure and Corrosion Performance of Mg–Zn Binary Alloys Prepared by Vacuum Evaporation

The Mg–Zn binary alloys prepared by vacuum evaporation were investigated in the initial state and after hot extrusion. The results of X-ray diffraction reveal that the composition of initial state alloys are α-Mg solid solution, MgZn, Mg7Zn3, and MgZn2 intermetallic compounds, respectively. As the compression treatment at the 360 °C (40 min, 10 Mpa), the size of the gray α-Mg phase is reduced from 100 μm to about 50 μm, which is surrounded by white intermetallic. At the same time, the corrosion current density is remarkably reduced, which means that the corrosion performance of the alloy is better. When the hot extrusion time raised from 4 h to 12 h (320 °C, 10 Mpa), the area of the deformation zone increased, and the precipitation amount of Mg7Zn3 distributed α-Mg matrix phases increased. Both the value of CPE1 and Rct are significantly reduced, indicated that the charge harder to transfer and the corrosion resistance of the alloy in Ringer's solution is weakened.

Effects of hot extrusion on microstructure and mechanical properties of Mg matrix composite reinforced with deformable TC4 particles

Abstract Mg matrix composites were often reinforced by non-deformable ceramic particles. In this paper, a novel Mg matrix composite reinforced with deformable TC4 (Ti–6Al–4 V) particles was fabricated and then extruded. The evolutions of microstructure and mechanical properties of the composite during hot extrusion were investigated. Hot extrusion refined grains and eliminated the segregation of TC4 particles. TC4 particles, as deformable particles, stimulated the nucleation of dynamic recrystallization during extrusion. However, since the deformation of TC4 particles partly released the stress concentrations around them, the recrystallized grains are just slightly smaller around TC4 particles than that away from them, which is evidently different from the case in Mg matrix composites reinforced by non-deformable ceramic particles. Compared with AZ91 matrix composites reinforced by SiC particles, the present composite possesses the superior comprehensive mechanical properties, which are attributed to not only the strong interfacial bonds between TC4p and matrix but also the deformability of TC4 particles.

Effect of hot extrusion on the characteristics of an Mg-3.0Zn-0.7Zr-1.0Cu alloy produced by powder metallurgy

The present study investigates the effect of hot extrusion on the physical, mechanical, and metallurgical characteristics of an as-extruded Mg-3.0Zn-0.7Zr-1.0Cu alloy. The Mg-3.0Zn-0.7Zr-1.0Cu samples were prepared through a powder metallurgy process which was followed by hot extrusion at 500°C using a suitably designed hydraulic press. Also, the properties of the alloy samples before and after extrusion were compared. The network structure broke down after extrusion and, hence, grains were more refined. This grain refinement is the result of matrix grain rupture, dynamic recrystallisation and the Zenner pinning mechanism. Acceptable tensile properties were noted after extrusion as a result of significant grain refinement and the precipitation of some intermetallic phases. After hot extrusion, the fracture mechanism changed from layer cracking to a mixed mode of cracking with cleaved facets and dimples.

Effect of hot extrusion on the characteristics of an Mg-3.0Zn-0.7Zr-1.0Cu alloy produced by powder metallurgy

Effect of hot extrusion on the characteristics of an Mg-3.0Zn-0.7Zr-1.0Cu alloy produced by powder metallurgy

Effect of Hot Extrusion on the Flow Behaviour of a Nickel-Based P/M Superalloy

This research investigated the effect of hot extrusion on the flow behaviour of nickel-based superalloy FGH4096 by hot compression experiments in the temperature range from 1020 to 1110 °C and strain rates ranging from 0.1 to 0.001 s-1. The influence of the hot extrusion on the initial microstructures, work hardening rate, strain rate sensitivity, and activation energy of deformation were discussed. The results show that the extruded microstructure is constituted by the fine dynamic recrystallisation of grains. The true strain-true stress curves show that the as-HIPed and as-HEXed FGH4096 superalloy present double flow stress peaks and discontinuous flow softening. The as-HEXed FGH4096 is easily dynamically softened at high temperatures and high strain rates compared with as-HIPed microstructures. As for the work hardening rate, the as-HEXed FGH4096 exhibits higher θ values than that of as-HIPed. It is beneficial to the homogenous deformation and grain refinement during subsequent turbine disk forging. Comparing to as-HIPed FGH4096, the highest strain rate sensitivity value of as-HEXed is 0.306 at 1110 °C. The isothermal superplastic forging of a P/M turbine disk may be carried out at this temperature. The deformation activation energy value of the as-HIPed FGH4096 is lower which means that dislocation sliding and climbing can be easily initiated in the as-HIPed alloy.

Improved properties of Ti-6Al-4V by combining isothermal equal-channel angular processing and hot-extrusion

ABSTRACTThe aim of this work was to study effects of hot extrusion on the microstructure of Ti-6Al-4V (wt-%) alloy processed by ECAP. Firstly, an isothermally Ti–6Al–4V alloy processed by Equal channel angular pressing(ECAP) was preheated at 950°C for 6 min and then hot extruded at 900°C. The hot extrusion minimised the grain size and maximised the mechanical strength. Therefore, it was demonstrated that hot extrusion of Ti-6Al-4V alloys that processed by ECAP could be performed without compromising any mechanical properties. Therefore, it is possible to use the ability to apply a reduced cross-section in hot extrusion for an Ti-6Al-4V processed by ECAP without concern about the reduction of properties.

Effect of Hot Extrusion on the Microstructure, Mechanical Properties, and Corrosion Behavior of Mg–11Li–3Al–2Zn–1.5Nd–0.2Zr Alloy

The microstructure, mechanical properties, and corrosion behavior of Mg–11Li–3Al–2Zn–1.5Nd–0.2Zr alloy before and after hot extrusion were studied. The results show that both as-homogenized and as-extruded alloys consist of β-Li, AlLi, MgLi2Al, and NdAl3 phases. The ultimate tensile strength and elongation of as-extruded alloy are 149.86 MPa and 42.33%, respectively, which are higher than those of as-homogenized alloy (132.99 MPa and 19%). The as-extruded alloy shows a better corrosion resistance with a lower hydrogen evolution rate and a higher charge transfer resistance. The improvement of mechanical properties and corrosion resistance of Mg–11Li–3Al–2Zn–1.5Nd–0.2Zr alloy after hot extrusion are as a result of the grain refinement and the uniform distribution of crumbled intermetallic phases.

Effect of hot extrusion and optimal solution treatment on microstructure and properties of spray-formed Al-11.3Zn-2.65Mg-1Cu alloy

The Zn-rich Al-11.3Zn-2.65Mg-1Cu alloy was prepared by spray forming rapid solidification technology and then processed by hot extrusion and heat treatment to T6-temper condition. The characteristics of spray-formed and extruded materials are systematically investigated, and accordingly, solution treatment parameters are derived at an intermediate temperature. The tensile results indicate that the alloy can reach yield strength as high as 807 MPa due to massive precipitation of ή phase which is attributed to the high supersaturation of the solutionized alloy because of the cumulative effect of spray forming and optimal solution treatment.

The effect of hot extrusion on the microstructure and anti-corrosion performance of LDHs conversion coating on AZ91D magnesium alloy

In this study, the effect of hot extrusion on the microstructure and anti-corrosion performance of LDHs (layered double hydroxides) conversion coating on AZ91D magnesium alloy was investigated by means of microscopic observation and electrochemical measurement. After hot extrusion, the refinement and rearrangement of the β-Mg17Al12 phase promotes the microgalvanic effect in the formation process, and the increase of dislocation density, twin, grain boundary and texture accelerates the dissolution rate of the Mg matrix. Due to microstructural differences, the electrochemical activity of various specimens in the formation process can be ranked as the increasing series: as-cast < transverse < longitude. Therefore, a thicker and more compact LDH conversion coating is formed on the longitudinal section of the extruded alloy, indicating the highest anti-corrosion performance.

Effect of hot extrusion on mechanical behaviour of boron nitride reinforced aluminium 6061-based metal matrix composites

In this present investigation Al 6061-based BN reinforced metal matrix composites were developed with 6 and 9 wt% of boron nitride. The Al 6061 was chosen as base material owing to its superior formability, light weight and moderate strength. Boron nitride was used as reinforcement keeping in mind its excellent wear and corrosion resistance along with superior strength and thermal properties. The stir casting method was adopted for development of composites since it is most flexible and universally accepted method for preparing castings economically. The developed composites were subjected to extrusion process. Mechanical properties were tested both before and after the extrusion to study the impact of extrusion process on properties of composites. It was observed that hardness and tensile strength of both casted and extruded samples were improved by the addition of the BN reinforcement. Whereas ductility of samples reduced with the increase of boron nitride concentration. Scanning electron microscopy (SEM) is used to identify the distribution of boron nitride (BN) and to study the fractured surfaces of Al 6061-BN metal matrix composites.