Ram Speed Research Articles

Microstructure and mechanical properties of a low-alloyed Mg–Zn–Al–Ca alloy: Effect of extrusion speed

A low-alloyed Mg-1.2Zn-0.6Al-0.1Ca (wt.%) alloy was extruded at 200 °C with different ram speeds (0.5–4.0 mm/s), and the microstructure and mechanical properties were studied systematically. Heterostructures with fine dynamic recrystallized (DRXed) grains and coarse unDRXed grains were achieved at lower ram speeds of 0.5 mm/s and 1.0 mm/s, and fully-DRXed microstructure was attained at 4.0 mm/s. Increasing the extrusion speed resulted in an increase in DRXed grain size from 0.9 μm to 3.8 μm, and a transformation of the DRXed texture component from <10 to 10>−<11–20> to a new orientation that deviated by approximately 14°. The sample extruded at 0.5 mm/s presented an excellent tensile yield strength (TYS) of 369 MPa along with a 7.8% elongation, which was mainly due to the high hetero-deformation induced (HDI) strengthening provided by its heterostructures. Increasing ram speed resulted in an improved elongation despite a decreased TYS. The reasons for the decreased strength with increasing extrusion speed were mainly associated with grain growth, reduced dislocation density and weakened HDI strengthening. The reasons for the improved ductility with increasing extrusion speed were largely due to the increased DRXed grains fraction with soft orientations.

Unexpected effects on creep resistance of an extruded Mg-Bi alloy by Zn and Ca co-addition: Experimental studies and first-principles calculations

In the present work, a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equivalent atom fraction with Bi. Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s. Room temperature mechanical properties and creep behaviors at 423 K were investigated. The results show that Zn and Ca co-addition shows little influence on average grain size and texture intensity but changes the dispersive Mg3Bi2 into Mg2Bi2Ca particles in different sizes and a lower density. Twinning is largely activated during room-temperature deformation. Consequently, a slightly decreased proof strength but tripled elongation is shown at room temperature. Unexpectedly, large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy. Stress exponent n = 4–5 indicates that the creep is a dislocation-climb controlled type. Post-mortem characterization on microstructure shows slip of dislocation 〈c + a〉 are also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy. Dynamic segregation and precipitation are also seen in both alloys. Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries. By contrast, Zn-rich needle-like precipitates are developed at most “ends” of 〈c + a〉 dislocations, which would hinder the further dislocation motions and thus improve the creep resistance. First-principles calculations were adopted and the results show that the thermal stability and thermomechanical properties of Mg2Bi2Ca are much better than that of Mg3Bi2. Stacking faults energy is lowered down with the co-addition of Ca and Zn, which could inhibit the rate of dislocation climb and cross-slip. As a result, the improved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys. Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition. These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.

Calibration of Swarm Ion Density, Drift, and Effective Mass Measurements

AbstractWe calibrate the Swarm Langmuir Probe Ion Drift, Density and Effective Mass (SLIDEM) products using the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC‐1) electron density measurements. SLIDEM combines electric current measurements from the Electric Field Instrument faceplate (situated on the ram‐facing side of the satellite) with ion admittance measurements from a spherical Langmuir probe to estimate ionospheric ion density, bulk ion drift parallel to the satellite trajectory in the polar regions, and effective ion mass at low and middle latitudes. SLIDEM processing includes an eight‐parameter empirical geometry model that expresses the corrections to the effective faceplate area and spherical probe radius arising from satellite‐plasma interactions. Validation of SLIDEM density by conjunctions with COSMIC density altitude profiles reveals systematic errors, with SLIDEM underestimating corresponding COSMIC data by around 10%. Using the same conjunctions to calibrate the SLIDEM density processor, a simple one‐parameter geometry model is obtained, which significantly reduces bias in ion density. This leads to reduced bias in the ion ram speed and in the effective mass, both of which are more consistent with empirical ionospheric models. We examined three models characterizing the variation of probe effective electrode current collection areas. Faceplate geometries are statistically indistinguishable from the physical faceplate cross section. Spherical Langmuir probe radius is effectively reduced by about 10% due to satellite‐plasma interactions. We recommend updating the SLIDEM processor to use a smaller value for the spherical probe's radius.

Charge weld evolution in hollow aluminum extrusion: Experiments and modeling

Charge welds occur in billet-to-billet extrusion processes due to the transition between successive billets. The material in this transition zone is typically characterized by substandard mechanical properties. In industrial practice, a specified length of the extruded profile is cut away and recycled as in-process scrap. Therefore, understanding the extrusion mechanisms affecting the properties of the charge weld is crucial to controlling product quality, reducing non-conformities and improving the extrusion yield. This paper provides new insights into thermo-mechanical mechanisms associated with charge weld of circular aluminum tubes. A large number of carefully-controlled, full-scale extrusion experiments were conducted in an industrial environment to research charge weld evolution mechanisms and influential parameters. In addition, a finite element (FE) model was developed to predict the charge weld evolution across the cross section and along the profile. The experimental and numerical results show good agreement in terms of the location of the charge weld within the extruded profile. Moreover, a comparison with analytical models in the literature reveals that the FE model provides a significantly more accurate prediction of the length of the extruded profile affected by the charge weld (‘scrap length’). Based on the validated FE model, a sensitivity study was done to explore the effect of process parameters on charge weld evolution, particularly focusing on material flow and dead metal zone. The results show that the ram speed influences the charge weld evolution, while changes in billet temperature are insignificant. In conclusion, the findings presented in this study provide new insights that serve as practical guidance to the mechanism of charge weld evolution. They also highlight the applicability and limitations of numerical and analytical methods in assessing industrial extrusion problems.

Microstructure and mechanical properties of longitudinal weld in 6005A aluminum alloy profile extruded by a porthole die

Porthole die extrusion experiments were carried out on 6005A aluminum alloy under the billet heating temperatures of 420–570 °C and ram speeds of 1–120 mm/min. The effects of extrusion parameters on the microstructure and mechanical properties in the longitudinal weld of profiles were investigated. It was found that the crystal orientation of longitudinal weld region showed the characteristics of gradient arrangement with different oriented grains wrapped in layers and symmetric along the welding line. The Copper{112}<111> grains are formed at the welding line under the combined effect of shear and compression, and the Goss{110}<100> grains are formed on their both sides due to dynamic recrystallization. A shear band is formed when part of metals flow through the 45° inclination angle of port bridge due to a sudden change in velocity, causing the Goss{110}<100> texture in local region to rotate to Brass{110}<112> texture. The 6005A aluminum alloy profiles mainly contain β (Mg2Si) phase, Q (Al3Mg9Si7Cu2) phase, AlCrMnSi phase and AlFeMnCrSi phase. Appropriately increasing billet heating temperature and ram speed can promote dynamic recrystallization and the dissolution of β-phase and Q-phase, thus improving the strength and hardness of the profile. However, when the billet heating temperature is too high, the strength and hardness are reduced instead due to grain coarsening. The profile extruded at billet heating temperature of 510 °C and ram speed of 120 mm/min has the best mechanical properties, with the tensile strength in 0° direction and hardness at the welding line of 179.93 MPa and 52.2 HV, respectively.

The Development of a High-Strength Mg-10.3Gd-4.4Y-0.9Zn-0.7Mn Alloy Subjected to Large Differential-Thermal Extrusion and Isothermal Aging.

The large differential-thermal extrusion (LDTE) process, a novel approach for efficiently fabricating a high-strength Mg-10.3Gd-4.4Y-0.9Zn-0.7Mn (wt.%) alloy, is introduced in this work. Unlike typical isothermal extrusion processes, where the ingot and die temperatures are kept the same, LDTE involves significantly higher ingot temperatures (~120 °C) compared to the die temperature. For high-strength Mg-RE alloys, the maximum isothermal extrusion ram speed is normally limited to 1 mm/s. This research uses the LDTE process to significantly increase the ram speed to 2.0 mm/s. The LPTE-processed alloy possesses a phase composition that is similar to that of isothermal extruded alloys, including α-Mg, 14H-type long-period stacking ordered (LPSO) and β-Mg5(Gd, Y) phases. The weakly preferentially oriented α-Mg grains in the LDTE-processed alloy have <101¯0>Mg//ED fibrous and <0001>Mg//ED anomalous textures as their two main constituents. After isothermal aging, high quantitative densities of prismatic β' and basal γ' precipitates are produced, which have the beneficial effect of precipitation hardening. With a yield tensile strength of 344 MPa, an ultimate tensile strength of 488 MPa, and an elongation of 9.7%, the alloy produced by the LDTE process exhibits an exceptional strength-ductility balance, further demonstrating the potential of this method for efficiently producing high-strength Mg alloys.

Effect of ram speed on surface quality and mechanical properties during extrusion of AA2024 alloy

AA2024 aluminium alloys are extensively used for aerospace applications that demand higher strength requirements. However, the productivity during extrusion of AA2024 is highly limited and is about one tenth in comparison with soft alloys such as AA6063. In the present work, numerical simulation studies were carried out to extrude solid bar of AA2024 alloy under different processing conditions i.e billet preheat, ramspeed. For simulation studies, the limits of extrusion being selected are extrusion ratio and product exit temperature. From the studies, it was observed that higher preheat temperatures have resulted in higher product exit temperatures. Subsequently, press trial on 1400 Ton extrusion press was conducted to correlate with simulation results and extrudates were characterized to observe the effect of ram speed and extrusion load on surface quality. Increase in ram speed during extrusion has resulted in increase in mechanical properties. However, at a ram speed higher than 1.5 mm/s, surface cracks appeared on the sample and safe limiting ramspeed was 1.5 mm/s.

Peripheral coarse grain formation in AA2024 and AA6063 aluminium alloys- A comparative study

Multifaceted mechanical and physical characteristics such as light weighting, high strength to weight ratio, electrical conductivity, and ease of fabrication have helped aluminium alloys to find its application in aerospace and automobile sectors. The most famous aluminium alloy used in extrusion is AA 6063 because of its 100% extrudability. AA2024 is from the family of hard alloys which finds its applications in the strength requirements and major alloying additions comprise of Cu, Mg which contributes to age/precipitation hardening phenomena. Because of its inherent nature of high strength, it is challenging to extrude. Extrusion is one of the major metals forming processes which involve several process parameters such as, temperature, strain rate, ram speed and post forming heat treatment operations. To attain the specific mechanical properties, microstructure of the extrudate is of utmost importance and evolution of the same needs to be understood. Heat treatable aluminium alloys series of 2xxx, 6xxx or 7xxx are prone to peripheral coarse grain structure, which is responsible for the loss of mechanical and corrosion performance. To eliminate PCG entirely or to minimize it is the fundamental interest of extrusion industries and to come up with a workable solution, it is necessary to twig the microstructure evolution of AA6063 and AA2024 alloy during extrusion and after heat treatment. The present work is aimed at comparative study of the PCG formation of press quenched samples in AA6063 and heat-treated (T6) samples of AA2024.

Achieving exceptional ultrahigh-strength in low-alloy Mg-1Al-1Ca-0.4Mn (wt%) alloy by regulating bimodal microstructure

A Mg-1Al-1Ca-0.4Mn (AXM1104, wt%) alloy extruded at 250 ℃ with a ram speed of 0.1 mm/s obtains a unique bimodal microstructure. As-extruded alloy exhibits a high tensile yield strength (YS) of 474 MPa but a low ductility of 2.1%, in which the YS exceeds conventionally extruded rare-earth-free Mg alloys reported so far. After annealing at 300 ℃ for 10 min, the annealed alloy achieves a good strength-ductility balance, with a YS of 426 MPa and an elongation of 5.4%. The ultrahigh YS of the as-extruded alloy is attributed to the combined strengthening efect of grain boundary, dislocation and texture, while the as-annealed alloy is mainly strengthened by both grain boundary strengthening and precipitation strengthening from planar Al2Ca nano phase.

Development of ultrahigh-strength low-alloy Mg-0.7Al-0.3Ca-0.4Mn (wt.%) alloy with excellent ductility via controlling extrusion temperature

Mg-0.7Al-0.3Ca-0.4Mn (AXM070304, wt.%) alloy was subjected to extrusion with a ram speed of 1 mm/s and an extrusion ratio of 25:1. The extrusion temperature varies from 170 °C to 400 °C. The influence of extrusion temperature on microstructure and mechanical properties of the dilute AXM070304 alloy was systematically explored. With raising the extrusion temperature, the average size of the dynamic recrystallized (DRXed) grains was increased, while the intensity of the basal fiber texture was decreased. When the extrusion temperature was escalated from 170 °C to 400 °C, the tensile yield strength (YS) of the low-alloy AXM070304 extrusion alloy was decreased from 437 to 246 MPa, while the elongation to failure (EL) was increased from 2.9 to 16.9%. The alloy extruded at 200 °C obtains an YS of 412 MPa, an ultimate tensile strength (UTS) of 418 MPa and an EL of 14.8%, exhibiting excellent ductility and ultrahigh strength. The ultrahigh YS was mainly due to the strengthening from ultra-fine recrystallized grains (0.61 μm) with grain boundary segregation of solute Al and Ca atoms. The growth of DRXed grains was inhibited mainly by the co-segregation of Al atoms and Ca atoms, nanosized Al2Ca and β-Mn particle phases at the grain boundaries. Plastic instability occurred under tensile loading in the ultrafine-grained AXM070304 alloy, which may be due to the fact that the grain boundary segregation of Al atoms and Ca atoms requires a high energy barrier for dislocation emission. Once the tensile stress reaches the peak value, the mobile dislocation density increases suddenly.

Abnormal grain growth behavior and mechanism of 6005A aluminum alloy extrusion profile

Peripheral coarse grain (PCG) structure is a common microstructural defect appearing in the aluminum alloy extrusion process, which seriously affects the mechanical properties of the profiles. In this work, a series of extrusion experiments and numerical simulations were conducted to investigate the influence of billet temperature and ram speed on the microstructure, mechanical properties and thickness of PCG layers of 6005A aluminum alloy profiles. The mechanism of abnormal grain growth (AGG) occurring on the surface and in the core of profiles was revealed. The result showed that lower ram speed could suppress the formation of coarse grains. The AGG on the surface of the profiles was activated by the shear deformation and lattice distortion derived from the friction on the interface between the profile and die. When the billet was heated to a relatively high temperature, dynamic recrystallization (DRX) was dominant, and the Cube{100}<100> and R-Cube{100}<110> grains underwent abnormal growth to form surface coarse grains. When the billet was heated to a relatively low temperature, the degree of static recrystallization (SRX) became stronger, and the Goss{110}<100> and R-Cube{100}<110> grains underwent abnormal growth to form surface coarse grains. The AGG in the core of profiles was activated by the large grain boundary misorientation and a strain gradient formed because the Cube{100}<100> recrystallized grains were surrounded by the Copper{112}<111> and Brass{110}<112> deformed grains. The second phases in the 6005A aluminum alloy extrusion profiles were mainly β (Mg2Si) and AlFeMnCrSi. As the billet temperature increased, more β phases dissolved into the aluminum matrix, thus enhancing the strength and hardness of the profiles. As the ram speed decreased, the thickness of PCG layers reduced, thus resulting in higher strength and hardness of the profiles. Due to the integrated effect of solution strengthening and grain refinement strengthening mechanisms, the combination of extrusion parameters for the profile to obtain the best mechanical properties was determined as 540 °C × 0.5 mm/s.

Investigation and Synthesis of Biowaste Composite by Squeeze Casting Process: Microstructure Evolution for Biomedical Applications

Objectives: To investigate the mechanical and microstructural behaviour of zinc hybrid composites. Zinc alloys are utilized in biomaterial development for implant applications due to their suitable corrosion properties. However, the advantages connected with hybrid reinforcements suggest further research. The objective is to determine the impact of Hydroxyapatite (HA) and Calcium Silicate (CS) derived from biowaste as hybrid reinforcement in Zn-1Mg- 0.2Ti alloy. The influence of hybrid reinforcement (HA&CS) was assessed in various weight percentages. Methods: Synthesis of the reinforcement (HA&CS) involved 10h milling and calcination at 1000ºC. Pure Zinc and Zn-1Mg-0.2Ti alloy with 5 wt. % and 10 wt. % (HA and CS) biomaterials were fabricated by the squeeze casting process. Hardness tests of the cast samples were conducted with a 1 kg (Hv) force and a 15-second dwell time. The compressive test was performed as per ASTM E9-19, with a ram speed 0.5mm/min. Findings: Results suggest that, among all three cases, Zn-1Mg-0.2Ti-(2.5 HA / 2.5 CS) composite exhibited favourable mechanical and microstructural properties. The Zn-1Mg-0.2Ti-(5 HA / 5 CS) composite density was 5.52 kg/m3, a significant 25% decrease compared to pure zinc metal. The Hardness value of Zn-1Mg- 0.2Ti-(2.5 HA / 2.5 CS) was 82Hv, which is 148% increase compared to pure zinc metal (33Hv). The compression tests demonstrated that the Zn-1Mg- 0.2Ti-(2.5 HA / 2.5 CS) exhibited the highest ultimate compression strength (364 MPa) and toughness modulus (131 MPa) due to sufficient adherence of the reinforcement with the matrix. Novelty: The novelty of the study was to introduce hybrid reinforcements (HA and CS) in the Zn-1Mg-0.2Ti alloy to increase its hardness and compressive strength. Zn-1Mg-0.2Ti-(2.5 HA / 2.5 CS) is a new hybrid composite compared to recent biomaterials. Furthermore, it can be recommended for implants in orthopaedic surgical applications. Keywords: Zinc Composites; Biodegradable Materials; Hydroxyapatite;Calcium Silicate (Wollastonite); Compressive Strength

Role of extrusion rate on the microstructure and tensile properties evolution of ultrahigh-strength low-alloy Mg-1.0Al-1.0Ca-0.4Mn (wt.%) alloy

Mg-1.0Al-1.0Ca-0.4Mn (AXM1104, wt.%) low alloy was extruded at 200 °C with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXM1104 alloy was systematically studied. With the increasing of extrusion rate, the mean dynamically recrystallized (DRXed) grain size of the low alloy and average particles diameter of precipitate second phases were increased, while the degree of grain boundary segregation and the intensity of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile yield strength (TYS) of the as-extruded AXM1104 alloy was decreased from 445 MPa to 249 MPa, while the elongation to failure (EL) was increased from 5.0% to 17.6%. The TYS, ultimate tensile strength (UTS) and EL of the AXM1104 alloy extruded at the ram speed of 1.5 mm/s was 412 MPa, 419 MPa and 12.0%, respectively, exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high TYS of 412 MPa was mainly due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly with increasing extrusion speed, which may be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXM1104 samples extruded at higher ram speed.

Metal flow hysteresis behavior and shape control strategy during porthole die extrusion of micro heat pipe

The shape control strategy of micro grooves is still unclear and challenging during the porthole die extrusion of grooved micro heat pipe (MHP). Through the simulation and experiment of porthole die extrusion of a MHP profile, the metal flow hysteresis behavior within micro features and the effect of ram speed and extrusion temperature on it and the resulting forming integrity was elucidated. Innovatively, Taguchi design and variance analysis (ANOVA) were introduced to determine their influence magnitude on the metal flow uniformity calculated by simulation results. The main findings are given below. The metal flow hysteresis derives from part feature size effect. The negligible friction-affected area during conventional extrusion severely slows down the metal flow within micro features during the MHP profile extrusion, which is due to the surge in the area ratio of the friction-affected area to the region in which it is located. Neither ram speed nor extrusion temperature can change the distribution of the friction-affected area. However, increasing ram speed multiplies the metal flow hysteresis and severely reduces the forming integrity, whereas extrusion temperature has little effect. Following this strategy, batch extrusion of the profile with micro-grooved width of 0.27 ± 0.02 mm was achieved in industrialized conditions.

Optimisation of cold extrusion process parameters on AA 2024 alloy using grey relational analysis

The present work investigates the influence of process parameters on cold extrusion process. Die angle (DA), ram speed (RS) and coefficient of friction (CoF) are chosen as input parameters. The output responses are extrusion force, damage factor, work piece displacement and extrusion time. AA 2024 material is considered as work piece material. The input process parameters are subjected to three levels of variation. Numerical simulations are performed by using DEFORMTM-3D. The simulations are conducted as per L27 orthogonal array. The percentage of contribution of DA, RS and CoF on extrusion force, damage factor, work piece displacement and extrusion time are analysed by using analysis of variance (ANOVA). Multi variable optimisation also done by using grey relational analysis (GRA). From the individual analysis, it is noticed that DA and RS have significant influence on extrusion force and work piece displacement whereas CoF is insignificant. However, the CoF shows significant impact on damage factor and extrusion time. The highest grey relation grade is obtained for experiment conducted at the 27th. The optimum combination of process parameter for extrusion force, damage factor, work piece displacement and extrusion time are 30ºDA, 4.8 mm/min RS and 0.1 CoF.

Behaviour of Aluminium Undergoing Cold Extrusion: A Review

Aluminium is widely used metal. Aluminium alloy is used in mechanical industries for bolts, nuts, rivets and many other things. Aluminium is cold extruded because of its benefits like very less oxidation, high strength because of working in cold temperatures, very closer tolerances, surface finish is good, and higher speeds of extrusion when specimen is intended to hot shortness. The main objective of this research is to perform cold extrusion on aluminium rods by considering different parameters, to obtain a superior product. Different parameters like the die angle, oils and ram speeds are considered for performing this experiment. The extruded products are compared and various tests like tensile, hardness, surface roughness are performed on the extruded products and the results are compared to decide better parameters for obtaining superior product. This paper is a summary of scholarly sources on cold extrusion and aluminium alloys. This research provides a clear view of the present knowledge and helps identify relevant*theories, methods, and gaps in existing research. It also describes the results of the research, and the conclusions are drawn from them.

Extrusion limit diagram of AZ91–0.9Ca–0.6Y–0.5MM alloy and effects of extrusion parameters on its microstructure and mechanical properties

Abstract An AZ91–0.9Ca–0.6Y–0.5 MM (AZXWMM91100) alloy, which has higher corrosion resistance, ignition resistance, and extrudability than a commercial AZ91 alloy, has been developed recently. In this study, the AZXWMM91100 alloy is extruded at various temperatures (300–400 °C) and ram speeds (1–14.5 mm/s), and the cracking behaviors, microstructure, and tensile properties of the extruded materials are systematically analyzed. On the basis of the pressure limit and surface and internal cracking limit, the extrusion limit diagram providing a safe extrusion processing zone is established. All of the materials extruded at temperatures and speeds within the safe extrusion processing zone have high surface quality and moderate tensile ductility with an elongation higher than 10%. Moreover, they have a fully recrystallized grain structure and contain undissolved particle stringers arranged parallel to the extrusion direction. The grain size of the extruded material does not show any relationship with the Zener–Hollomon parameter (Z). However, the yield strength (YS) of the extruded material is inversely proportional to the logarithm of the Z value, and their relationship is expressed as YS = −31.2•log(Z) + 536. These findings may broaden the understanding of the AZXWMM91100 alloy with excellent chemical and physical properties and provide valuable information for the development of high-performance extruded Mg products using this alloy.

Microstructure and Mechanical Properties of ZK60 Mg Alloy Processed by Cyclic Expansion-Extrusion (CEE) at Different Temperatures

In this work, the cyclic expansion extrusion (CEE) process was applied to ZK60 Mg alloy. The correlation between the evolved microstructure and mechanical properties was investigated. The CEE process was performed at a constant ram speed (15 mm/min) and at different processing temperatures (190, 270, and 350 °C). Optical and scanning electron microscopes, X-ray diffraction instruments, Vickers hardness tester, and tensile testing machine were utilized to examine the influence of CEE processing temperature on the characteristics of ZK60 Mg alloy. The XRD analysis showed that two phases were presented in the matrix of ZK60 Mg alloy, namely α-Mg and MgZn2, in small amounts. The CEE process reduced the size of α-Mg grains due to dynamic recrystallization, especially at the processing temperature of 190 °C. A slight coarsening of the α-Mg grains was observed with increasing processing temperature to 270 and 350 °C. The hardness value ​​of ZK60 Mg alloy was enhanced by about 11 to 19% using the CEE process compared to the as-extruded sample. The processing temperature greatly affected the mechanical properties, where a significant improvement of about 24% yield strength, 9% ultimate tensile strength, and 38% elongation was observed using a processing temperature of 190 °C. The characterization of the tensile fracture surface of the tested samples indicated that the ductile-brittle fracture mode was responsible for the failure.

Dry Wear Behaviour of the New ZK60/AlN/SiC Particle Reinforced Composites.

This study deals with the microstructure, mechanical, and wear properties of the extruded ZK60 matrix composites strengthened with 45 µm, 15% silicon carbide particle (SiC) and 760 nm, 0.2-0.5% aluminium nitride (AlN) nanoparticle reinforcements. First, the reinforcement elements of the composites, SiC and AlN mixtures were prepared in master-magnesium powder, and compacts were formed under 450 MPa pressure and then sintered. Second, the compacted reinforcing elements were placed into the ZK60 alloy matrix at the semi-solid melt temperature, and the melt was mixed by mechanical mixing. After the melts were mixed for 30 min and a homogeneous mixture was formed, the mixtures were poured into metal moulds and composite samples were obtained. After being homogenized for 24 h at 400 °C, the alloys were extruded with a 16:1 deformation ratio at 310 °C and a ram speed of 0.3 mm/s to create final composite samples. After microstructure characterization and hardness analysis, the dry friction behavior of all composite samples was investigated. Depending on the percentage ratios of SIC and AlN reinforcement elements in the matrix, it was seen that the compressive strength and hardness of the composites increased, and the friction coefficient decreased. While the wear rate of the unreinforced ZK60 alloy was 3.89 × 10-5 g/m, this value decreased by 26.2 percent to 2.87 × 10-5 g/m in the 0.5% AlN + 15% SiC reinforced ZK 60 alloy.

Synthesis of Al7075/TiB2-Al2O3 In-Situ Hybrid Composite by Stir Casting Method

In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.