Compact Extrusion Research Articles

Composite of Magnesium and Carbonate Apatite for Biodegradable Bone Implants: A Comparative Study on Sintering and Extrusion Techniques

Developing biodegradable bone implants using magnesium-based materials has garnered significant attention in research. Magnesium offers favorable properties, such as low density, biocompatibility, elastic modulus like bone, and high toxicity limits. However, improvements are needed in mechanical properties and degradation rate. This study focuses on enhancing these properties by developing a novel composite of magnesium with carbonate apatite (CA) reinforcement, Mg/5CA. Compared to hydroxyapatite (HA), CA offers better absorption and avoids fibrotic tissue formation. However, CA undergoes carbonate decomposition during sintering, leading to composite degradation. To address this, an extrusion process is employed to prevent carbonate decomposition. The advanced sintering and extrusion compaction processes are compared for the Mg/5CA composite, examining density, microstructure, hardness, compressive strength, and biocorrosion. Results demonstrate that extrusion increases relative density while CA slightly reduces it. Microstructural analysis reveals finer and elongated grains, tighter bonding between CA and Mg particles, and reduced microporosity in the extruded composite. Mechanical properties, including hardness distribution and compressive strength, are improved in the extruded composite, and the degradation rate decreases compared to sintering. Overall, the extrusion process effectively enhances Mg/5CA composite properties, positioning it as a promising manufacturing technique for biodegradable implant materials. This research contributes to the development of advanced biodegradable implants, which can have significant applications in the field of medical science. Further investigations in this area can contribute to the ongoing advancements in biodegradable implant technology.

The effect of adding Sn on the mechanical properties and microstructure of the titanium

Ti-XSn (X = 0, 5, 10, 15) (wt. %) alloys were prepared by blending TiH2 and Sn powder compact extrusion. The effect of adding tin (Sn) on the microstructure and mechanical properties of titanium has been investigated by optical microscopy and tensile tests. The lamellar thickness (10 to 6.6 µm) of the Ti reduced after adding Sn and according to the Hall-Petch equation the yield strength (548.2 to 801.3 MPa) and microhardness (233.2 to 310 HV) of the Ti is increased with increasing the tin (Sn) content.

Improving strain hardening capacity of high-strength Ti–6Al–4V alloy by a dual harmonic structure

By TiH2/Al60V40 powder processing, in-situ dehydrogenation, and powder compact extrusion, we successfully fabricate a Ti–6Al–4V (wt.%) alloy with a dual harmonic structure. Such multilevel structural heterogeneity is attained by suppressing the stabilization effect of the residual hydrogen on β-Ti phase, through controlling the prior β grain sizes and interstitial element contents. It is demonstrated that this dual harmonic structure is beneficial in alleviating mechanical mismatch between hetero-domains and fully exploiting the hetero-deformation induced hardening, thereby leading to a high strain hardening rate and large uniform elongation. As a result, the material exhibits a better strength-ductility synergy (an ultimate tensile strength of 1338 MPa and a uniform elongation of 7.7%) than both the one-level harmonic and homogeneously structured materials. The present ‘tailoring structural heterogeneity through manipulating hydrogen-enabled eutectoid transformation’ strategy offers a different pathway to design and fabricate novel heterogeneously structured titanium alloys with a high strength-ductility synergy.

The effects of extrusion ratio and heat treatment on microstructures and tensile properties of a powder metallurgy Fe–22Mn steel

Powder metallurgy Fe–22Mn (wt.%) steel rods were fabricated by powder compact extrusion followed by heat treatment, and their microstructures and tensile properties were investigated. The microstructure of the as-extruded rods consisted of γ-austenite, ε-martensite, α'-martensite and a dispersion of ferrous manganese oxide (FMO) particles. By increasing the extrusion ratio from 9:1 to 16:1, the volume fractions of γ and ε increased significantly, while that of α' decreased significantly, which is due to more Mn atom diffused into the γ phase and improved its stability. This situation led to a significant decrease in yield strength without much change of the tensile strength and ductility. γ→ε and ε→α' transformations occurred during plastic deformation, resulting in a strengthening of the strain hardening capacity. The γ→ε transformation occurred only when the strain was <0.1, and beyond this strain, the volume fraction of γ decreased to a level that would not allow further phase transformation in γ. Annealing at 1200 °C for 1 h makes Fe atoms undergone segregation in FMOs, causing an obvious decrease of the hardness and Young’ s modulus of the FMO particles to a level lower than that of the matrix, which brings more severe damage to the ductility of the material.

Effects of the Extrusion Ratio on the Microstructure and Mechanical Properties of the Columnar Network Structure Tibw/Ta15 Composites Fabricated by Powder Compact Extrusion

Effects of the Extrusion Ratio on the Microstructure and Mechanical Properties of the Columnar Network Structure Tibw/Ta15 Composites Fabricated by Powder Compact Extrusion

Optimization of biocorrosion resistance and mechanical properties of PM Ti–XAl–2Fe–3Cu alloys by response surface methodology

In the current study, the biocorrosion resistance and mechanical properties of the Ti–XAl–2Fe–3Cu (wt%) (X = 6, 4, 2 wt%) alloy produced by powder compact extrusion of blended elemental powders were optimized by using the response surface methodology in order to gain the best combination of processing parameters. To run the optimization process, central composite design with three equal levels of oxygen, hydrogen and aluminum was used and, by employing ANOVA, the analysis of variance was implemented. The results showed that the content of aluminum has a significant effect on the microstructure, mechanical properties, biocorrosion resistance and fracture behavior of the extruded rods. The highest aluminum content corresponds to the highest alloy strength and biocorrosion resistance. This was due to the reduction of the lamella thickness and of the material colonies as the aluminum content increases. Also, by running the experimental and optimization tests, the mechanical properties resulted 1245 MPa in yield strength and 1340 MPa in ultimate tensile strength with 0.1 µAcm−2 in corrosion current.

Experimental Study of Energy Evolution at a Discontinuity in Rock under Cyclic Loading and Unloading.

Energy is often dissipated and released in the process of rock deformation and failure. To study the energy evolution of rock discontinuities under cyclic loading and unloading, cement mortar was used as rock material and a CSS-1950 rock biaxial rheological testing machine was used to conduct graded cyclic loading and unloading tests on Barton’s standard profile line discontinuities with different joint roughness coefficients (JRCs). According to the deformation characteristics of the rock discontinuity sample, the change of internal energy is calculated and analyzed. The experimental results show that under the same cyclic stress, the samples harden with the increase in the number of cycles. With the increase of cyclic stress, the dissipated energy density of each stage gradually exceeds the elastic energy density and occupies a dominant position and increases rapidly as failure becomes imminent. In the process of increasing the shear stress step-by-step, the elastic energy ratio shows a downward trend, but the dissipated energy is contrary to it. The energy dissipation ratio can be used to characterize the internal damage of the sample under load. In the initial stage of fractional loading, the sample is in the extrusion compaction stage, and the energy dissipation ratio remains quasi-constant; then the fracture develops steadily, the damage inside the sample intensifies, and the energy dissipation ratio increases linearly (albeit at a low rate). When the energy storage limit is reached, the growth rate of energy dissipation ratio increases and changes when the stress level reaches a certain threshold. The increase of the roughness of rock discontinuity samples will improve their energy storage capacity to a certain extent.

Microstructures and mechanical properties of high strength Ti-XAl-2Fe-3Cu alloys fabricated by powder compact extrusion

Ti-XAl-2Fe-3Cu (X = 2.7, 4 wt%) alloys with a high tensile yield strength of up to 1150 MPa were synthesized using powder compact extrusion from blended TiH2 and elemental powders. The microstructures and mechanical properties of the extruded rods without and with a homogenization heat treatment at 1000 °C for 1 h followed by furnace cooling were investigated. It was found that the Al content and heat treatment had significant effects on the microstructures and mechanical properties. With increasing the Al content from 2.7 to 4 wt%, the average lamellar colony size and lamellar thickness of the as-extruded Ti-XAl-2Fe-3Cu alloy decreased from 442.4 to 224.1 µm and 6.7–5.2 µm respectively. The heat treatment increased the lamellar thickness as well as the level of partitioning of Fe and Cu between α and β phases. As a result of the microstructural changes, increasing Al from 2.7 to 4 wt% caused a slight increase in the strength of Ti-XAl-2Fe-3Cu alloys without changing the ductility, while the heat treatment slightly reduced the strength of the alloys, but clearly increased their tensile ductility. The correlation between microstructures and mechanical properties is discussed.

Enhancement of tensile strength and ductility of titanium with a bimodal structure

A bimodal structured commercial pure (CP) titanium consisted of coarse grained α Ti plates with an average thickness of 1.60 μm and ultrafine structured β transformed domains was fabricated by high energy mechanical milling of a TiH2 powder, in-situ dehydrogenation of TiH2 and powder compact extrusion of the dehydrogenated Ti. It exhibited a high yield strength (YS) and ultimate tensile strength (UTS) of 731 and 903 MPa respectively and an appreciable tensile ductility (elongation to fracture: 8.8%). After vacuum annealing at 700 °C for 6 h, the hydrogen content was reduced from 0.36 wt% to 001 wt% and the microstructure of the titanium changed into another type of bimodal structure consisting of coarse equiaxed grains with an average size of 5.19 μm and ultrafine grains with an average size of 0.325 μm. This microstructural change caused the YS and UTS of the CP titanium to clearly increase to 794 and 932 MPa, and its tensile ductility to increase drastically (elongation to fracture：26.2%). Analysis of the correlation between the microstructures, tensile properties and fracture behavior of the CP titanium suggests that the drastic tensile ductility improvement with the change of microstructure after annealing can be attributed to the high capacity of equiaxed Ti grains to accommodate plastic deformation due to their large number of crystallographic orientations than the coarse grained α-Ti plates which have a limited number of crystallographic orientations. In the meantime, the grain boundary strengthening of the ultrafine grained domains of the annealed CP titanium still ensures a high strength.

Harmonically structured Ti–6Al–4V alloy with ultrahigh strength fabricated by thermomechanical consolidation of mechanically milled TiH2/Al60V40 powder blend

Novel harmonically structured Ti–6Al–4V alloy samples consisting of ultrathin lamellar structured cores embedded in coarse-grained shells were fabricated through high energy mechanical milling of TiH2/Al60V40 powder blend and powder compact extrusion of the mechanically milled powder at 1000 and 1100 °C. Some samples extruded at 1100 °C were vacuum annealed subsequently at 700 °C for adjusting microstructural parameters. The microstructure/mechanical properties correlations of the as-extruded and annealed samples were systematically investigated. It was proposed that the formation of the harmonic structure can be attributed to the stabilization effect of the residual hydrogen on β-Ti phase and the suppressed eutectoid transformation. In terms of the mechanical properties, the ultrahigh tensile fracture stress of harmonically structured samples was ascribed to the interface strengthening of ultrathin lamellar structured cores together with a relatively high content of oxygen. Thanks to the hetero-deformation induced hardening provide by coarse-grained shells, the strain localization was delayed. Specifically, by improving strain partitioning among heterogeneous domains, a better combination of strength and ductility was achieved. As a result, a tensile fracture strength of 1431 MPa and a uniform elongation of 4.5% were attained in an extruded and subsequently annealed Ti–6Al–4V alloy sample.

Annealing hardening and softening of an ultrafine grained Cu-4.5vol.%Al2O3 nanocomposite

Samples from an ultrafine-grained Cu-4.5vol.%Al2O3 nanocomposite rod fabricated by powder compact extrusion were annealed at 400 and 700 °C for 15 min respectively, and their microstructure and mechanical properties were investigated. It shows that the dislocation density decreased and Al2O3 nanoparticles severely coarsened after 700 °C annealing, leading to simultaneous decrease of both strength and tensile ductility (annealing softening). On the other hand, annealing at 400 °C also caused a dislocation density decrease, but without Al2O3 nanoparticle coarsening, and this leads to an unexpected and significant increase of both strength and ductility (annealing hardening). It is believed that the interaction between the dislocations and Al2O3 nanoparticles within the as-extruded sample weakens the Orowan strengthening, while the dislocation density decrease caused by 400 °C annealing allows the enhancement of the Orowan strengthening effect with a benefit of simultaneous increase of both strength and tensile ductility.

Improving the mechanical behavior of an ultrafine grained Cu-6.4vol.%NbC nanocomposite by hot rolling

To improve the mechanical behavior of the ultrafine grained Cu-6.4vol.%NbC nanocomposite rods fabricated by powder compact extrusion, they were hot-rolled into sheets at 800 and 1000 °C respectively. Rolling at 800 °C caused the ultimate tensile strength (UTS) of the nanocomposite to clearly decrease from 868 to 755 MPa without changing the tensile ductility, while rolling at 1000 °C caused a similar change of the UTS, but increased the elongation to failure (ETF) of the nanocomposite drastically, from 6% to 12.6%. Such a significant improvement in ETF while still maintaining a high strength was ascribed to the elimination of the residual unconverted interparticle boundaries and the nanoparticle stablilized nanocrystalline microstructure.

Heat Treatment, Impact Properties, and Fracture Behaviour of Ti-6Al-4V Alloy Produced by Powder Compact Extrusion.

The mechanical properties of titanium and titanium alloys are very sensitive to processing, microstructure, and impurity levels. In this paper, a blended powder mixture of Ti-6Al-4V alloy was consolidated by powder compact extrusion that involved warm compaction, vacuum sintering, and hot extrusion. The as-processed material with an oxygen content of 0.34 wt.% was subjected to various annealing treatments. The impact toughness of heat-treated material was determined using Charpy V-notch impact testing at room temperature. An emphasis was placed on establishing a relationship among fracture behaviour, microstructure, and the resulting properties of tested material. From the results, it is apparent that the highest impact toughness value of 19.3 J was achieved after α/β annealing and is comparable with typical values given in the literature for wrought Ti-6Al-4V. In terms of fracture behaviour, it is quite apparent that the crack propagation behaviour of powder-produced material is rather complex compared with the limited amount of data reported for ingot counterparts.

A novel way for fabricating ultrafine grained Cu-4.5 vol% Al2O3 composite with high strength and electrical conductivity

Ultrafine grained Cu-4.5 vol% Al2O3 bulk composite samples were fabricated by a novel way involving three steps: (i) dealloying of a Cu-50wt.%Al alloy powder to produce a nanocrystalline Cu-0.8wt.%Al-1.5wt.%O powder; (ii) heat treatment of the as-dealloyed powder using two different routes to obtain Cu-Al2O3 composite powders with Al2O3 particles distributed either at Cu grain boundaries or within Cu grains, and (iii) consolidation of the powders by powder compact extrusion. The microstructures, mechanical properties and electrical conductivity of the composite samples were investigated. The composite sample with a dispersion of intragranular Al2O3 nanoparticles exhibited an excellent combination of a high tensile strength (522 MPa), good ductility (elongation to fracture: 8.2%) and a high electrical conductivity (90%IACS). The correlation among the microstructure, mechanical properties and electrical conductivity is discussed.

Numerical Simulation and Experimental Research on Microstructural Evolution During Compact Hot Extrusion of Heavy Caliber Thick-Wall Pipe

Compact hot extrusion (CHE) process of heavy caliber thick-wall pipe is a new material-saving production process. In order to reveal the optimum hot extrusion parameters in CHE process, the effects of the extrusion parameters on the microstructural evolution are investigated systematically. The metadynamic recrystallization (MDRX) kinetic models and grain size models of as-cast P91 steel are established for the first time according to the hot compression tests performed on the Gleeble-3500 thermal-simulation machine. Then a thermal-mechanical and micro-macro coupled hot extrusion finite element (FE) model is established and further developed in DEFORM software. The results indicated that the grain size of the extruded pipe increases with the increasing of initial temperature and extrusion speed, decreases when extrusion ratio increases. Moreover, the grain size is more sensitive to the initial temperature and the extrusion ratio. The optimum hot extrusion parameters are including that, the initial extrusion temperature of 1250 °C, the extrusion ratio of 9 and the extrusion speed of 50 mm/s. Furthermore, in order to verify the simulation precisions, hot extrusion experiment verification on the heavy caliber thick-wall pipe is carried out on the 500 MN vertical hot extrusion equipment. The load–displacement curve of the extrusion process and the grain sizes of the middle part extruded pipe are in good accuracy with the simulation results, which confirms that the hot extrusion FE models of as-cast P91 steel could estimate the hot extrusion behaviors. The proposed hot extrusion FE model can be used to guide the industrial production research of CHE process.

Microstructure and Mechanical Properties of Ti-6Al-4V Rods Fabricated by Powder Compact Extrusion of TiH2/Al60V40 Powder Blend

Nearly fully dense Ti-6Al-4V rods were fabricated by powder compact extrusion of TiH2/Al60V40 powder blend. The microstructure, mechanical properties, and fracture behaviors of the Ti-6Al-4V rods extruded at various temperatures from 1100 °C to 1400 °C were investigated. The results showed that with the extrusion temperature of 1100 °C, undissolved V-rich particles still existed in the microstructure, but they disappeared once the extrusion temperature increased to 1200 °C. Nearly complete dehydrogenation of TiH2 was achieved during rapid induction heating, holding, and extrusion. With increasing the extrusion temperature, prior β grain sizes and α/β lamella colony sizes increased dramatically, while the change of α lamella thickness was much less significant. The correlation between microstructure and mechanical properties suggests that α/β lamella interfaces, instead of colony boundaries, are responsible for strengthening. The coarse prior β grains whose sizes reached 150 μm had a deleterious effect on the tensile ductility due to localized deformation, as evidenced by the intergranular fracture. The rod extruded at 1200 °C had the best elongation to fracture of 9.3 pct while still keeping a high yield strength of 969 MPa and ultimate tensile strength of 1102 MPa.

The Effect of Heat Treatments on Microstructure and Mechanical Properties of As-Extruded Ti-6Al-4V Alloy Rod from Blended Elemental Powders

In this study, Ti-6Al-4V bars were first prepared by extrusion of powder compacts from blended powder mixtures in the beta phase region, then the as-extruded bars were heat-treated following four different conditions: beta quenching and aging (βQA), broken up structure (BUS) treatment, solution treatment and aging (STA) and recrystallization annealing (RA). The effect of the heat treatments on microstructure and mechanical properties was studied using optical microscopy, scanning electron microscopy, and mechanical test to determine which heat-treatment condition has the greatest impact on the mechanical properties of the as-extruded Ti-6Al-4V alloy. The results show that the as-extruded condition has the best balance of strength (1120 MPa of UTS) and ductility (11% of elongation to failure). βQA and STA lead to a slight increase in strength but ductility decreases considerably. After BUS and RA treatments, both strength and ductility are reduced. The relationship between processing, microstructure and properties was studied, and their implications towards fatigue behaviour and fracture toughness were discussed.

Doping Ti to achieve microstructural refinement and strength enhancement in a high volume fraction Y2O3 dispersion strengthened Cu

In this work, high volume fraction Y2O3 dispersion strengthened Ti-free and Ti-doped Cu samples were prepared by mechanical alloying, high temperature heat treatment and powder compact extrusion to study the role of alloying Ti element on microstructures, mechanical properties and electrical conductivity of the extruded samples. It is found that the addition of a small amount of 0.4 wt.%Ti effectively suppresses the coarsening of Y2O3 particles during material fabrication, which produces smaller and more uniform oxide particles distributed in a homogeneous ultrafine grained Cu matrix. However, a heterogeneous Cu matrix microstructure, consisting of elongated micrometer-scale Cu grains and equiaxed ultrafine Cu grains, is observed in the Ti-free sample due to significant coarsening of the Y2O3 particles. The different microstructural features of the two extruded samples lead to distinctively different mechanical behaviors and electrical conductivities. The energy dispersive X-ray spectrometry elemental and high resolution transmission electron microscopy analysis suggest that the stabilizing mechanisms of the Y2O3 particles involve both the segregation of Ti atoms to the surface layers of large Y2O3 particles and dissolution of Ti atoms into small Y2O3 particles to form complex particles.

On microstructural evolution and mechanical properties of Ti-5Al-5V-5Mo-3Cr alloy synthesised from elemental powder mixtures

In this paper, we explored to prepare a multi-compositional titanium alloy, Ti-5Al-5V-5Mo-3Cr (Ti-5553), by powder compact extrusion from elemental powder mixtures, and investigate the microstructure variation during the synthesising process and after post heat treatments and the changes of mechanical properties. XRD, OM and SEM were used to analyse the phase constitutions and microstructures of the Ti-5553 alloy at different processing conditions, and tensile tests were conducted to examine their mechanical properties. The results showed that a homogeneous Ti-5553 alloy was successfully produced by powder compact extrusion from the powder mixtures, β phase was mainly contained in the hot-pressed and 1200°C-extruded Ti-5553 alloy and had an equiaxed microstructure. Different types of α phase precipitated from the β matrix after heat treatment, and this significantly changed the microstructures and improved the mechanical properties of the extruded Ti-5553 alloy, with yield strength of 1250 MPa and ultimate strength of 1300 MPa for the alloy treated at 675 °C for 2 h, and the ductility of about 6.1% for the alloy treated at 780 °C for 2 h.

Effect of extrusion temperature on microstructure and properties of an ultrafine-grained Cu matrix nanocomposite fabricated by powder compact extrusion

Ultrafine-grained Cu–5 vol%Al2O3 nanocomposite rods were fabricated by a combination of high-energy mechanical milling of Cu and Al2O3 powders and powder compact extrusion at 300, 500, 700 and 900 °C. The extruded rods were investigated to evaluate microstructures, mechanical properties, fracture behavior and electrical resistivity. It was found that the extrusion temperature has a pronounced effect on Cu grain growth, Al2O3 particle coarsening and particle distribution. High-temperature extrusion leads to directional coarsening of certain grains. As such, a heterogeneous matrix structure of large elongated and equiaxed grains is created, and this unique matrix structure brings beneficial effects in tensile ductility and electrical resistivity. While Al2O3 dispersions in the matrix improve the overall performance of the nanocomposite, an incorrect selection of the extrusion temperature may have detrimental effects on yield strength and resistivity. Tensile fractography investigation shows that the presence of Al2O3 results in failures along grain boundaries. This study also provides a framework for modeling the mechanical and electrical properties of such complex matrix structures. Modeling tools/formulae can be used to predict mechanical/electrical properties via microscopic characteristics and hence can also be used to understand the effect of processing variables.