Development and Characterisation of Natamycin Mini-Matrices Prepared by Hot-Melt Extrusion for Vaginal Delivery

In this study, bioadhesive mini-matrices of natamycin were prepared for vaginal application by hot-melt extrusion. In addition, melt viscosity measurements, thermogravimetric analysis, in vitro drug release studies and in vitro mucoadhesion test were performed. High molecular weight grades of KlucelTM hydroxypropylcellulose were used as a thermoplastic polymer. TEC and PEG 400 were chosen as plasticizer. According to the obtained results of melt viscosity measurements, the maximum torque of extrudates prepared using PEG 400 increased with increasing drug loading. The thermo-gravimetric analyses showed that natamycin is stable up to 198℃ and this result gives the opportunity to hot melt extrussion process at 90℃. In vitro drug release results showed that the release was extended up to 72 hours and drug release rate increased with increasing drug loading. In respect to the in vitro mucoadhesion test results, the values of work of mucoadhesion were found high as 771,977 mN.mm, 753,199 mN.mm, 686,356 mN.mm for the prepared hot melt extruded mini-matrices. Our results showed that the developed formulations were found worthy of further studies.

Hot-melt extrusion promotes dissolution,extends“spring-parachute”process and inhibits crystallization in supersaturating microparticle systems

Despite the potential advantages of amorphism-induced supersaturation,the merit of new amorphiza-tion formation methods on the properties of the amorphous drug including the stability of the amor-phous state,dissolution/solubility,supersaturation,and"spring-parachute"process is still poorly understood,particularly for certain amorphous supersaturating drug delivery systems(aSDDS).The present work aimed to explore the detailed merit of current attractive amorphization manufacturing methods(i.g.,hot-melt extrusion(HME)technique)on the property improvement of aSDDS in form of amorphous solid dispersion microparticles by employing a model Bcs II drug nitrendipine and a polyvinylpyrrolidone-based model polymer copovidone.Many asDDS systems were developed by various methods,and their physicochemical properties were characterized by SEM,PXRD and DSC.HME-triggered amorphization induced superior supersaturation by the observation of the highest dissolution and solubility.HME induced the optimal supersaturation duration by the observed greatest extension of"spring-parachute"process(e.g,maximum AUCspring-parachute).HME technique is comparable with other techniques for the stabilization of amorphous state during storage.All aSDDS systems by HME and other methods showed improved long-term stability of the amorphous state in comparison to the pure amorphous drug.Fourier transformation infrared spectroscopy,Noyes-Whitney equation,nucleation theory and Gibbs free energy of transfer(△G)were used to analyze the underlying mechanisms.Mo-lecular mechanism studies indicated that HME caused a stronger crystallization inhibition effect in the asDDS systems than other methods,but molecular interaction is not a dominant mechanism for property enhancement caused by HME.For the mechanism associated with the polymer itself(PVPVA64),it could inhibit the drug recrystallization,solubilize the drug spontaneously and cause the improved molecular interactions in all aSDDS systems.This study provided a deep insight into detailed advantage of HME-triggered supersaturation/amorphization and facilitated the applications of the technique both in the field of particuology and in pharmaceutical industry.

Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

Investigation of high rate mechanical flow followed by ignition for high-energy propellant under dynamic extrusion loading

Investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident stimulus.Secondly, evaluates the risk of a shell crevice in a solid rocket motor(SRM) under a falling or overturning scene. In the present study, an innovative visual crevice extrusion experiment is designed using a dropweight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. Based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.

Deformation mechanisms and microstructural characteristics of AZ61 magnesium alloys processed by a continuous expansion extrusion approach

The unique continuous extrusion-based severe plastic deformation approaches were proposed recently to process high-performance magnesium(Mg)alloys,while the in-depth deformation mechanisms under such complicated thermomechanical conditions were not well understood.In the present work,the fundamental deformation behaviors of AZ61 Mg alloy from 25 to 400°C were firstly examined under uniaxial compression deformation.Then the deformation mechanisms and microstructural characteristics of AZ61 Mg alloy during continuous expansion extrusion forming(CEEF)were systematically investigated by microstructural observations,finite element and cellular automata simulations.The results showed that the continuous evolutions of temperature,larger strain level and complex stress state with strain rate range of 0∼5.98 s−1 during CEEF brought the distinctive dynamic recrystallization behaviors and texture development in AZ61 Mg alloy,which were different to that of uniaxial compression deformation.In details,a remarkable grain refinement was achieved via CEEF processing due to the simultaneous actions of continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX).Gradually enhanced CDRX were observed from center to edge region,which had significant effects on the texture distribution and texture strength.The c-axis of most grains rotated under distinctive shear strain following parabolic metal flow,resulting in stable fiber texture.In addition,the evolution of the internal texture of the alloy led to an obvious increase in the Schmid factor for the activation of basalc+aslip system.©2022 Chongqing University.Publishing services provided by Elsevier B.V.on behalf of KeAi Communications Co.Ltd.

Predictive factors for coronal and sagittal graft extrusion length after using tendon autograft for medial meniscus reconstruction

BACKGROUND Meniscus extrusion occurs in most elderly individuals and most patients after meniscus allograft transplantation.The risk factors and correlative factors of meniscus extrusion have been extensively studied.However,for using tendon autograft for meniscus reconstruction,both graft type and surgical method are different from those in previous studies on meniscus extrusion.AIM To identify predictive factors for coronal and sagittal graft extrusion length after using tendon autograft for medial meniscus reconstruction.METHODS Ten patients who underwent medial meniscus reconstruction with tendon autograft were selected for this retrospective observational study.The graft extrusions and potential factors were measured and correlation and regression analyses were performed to analyze their relationships.RESULTS The medial graft extrusion correlated with the preoperative bilateral hip-kneeankle angle difference,preoperative Kellgren-Lawrence grade,preoperative relative joint space width,and preoperative bilateral medial edge incline angle difference.The anterior graft correlated with the anterior tunnel edge distance at 1 week after operation.The posterior graft extrusion correlated with the preoperative bilateral hip-knee-ankle angle difference,preoperative relative joint space width,and posterior tunnel edge distance at 1 week after operation.The mean graft extrusion correlated with the preoperative bilateral hip-knee-ankle angle difference and preoperative relative joint space width.The preoperative joint space width and anterior and posterior tunnel edge distance at 1 week can be used to predict the medial,anterior,posterior,and mean graft extrusion length.CONCLUSION The preoperative joint space width and tunnel position can be used to predict the coronal and sagittal graft extrusion length after using tendon autograft for medial meniscus reconstruction.

Extrusion 3D printing of carbon nanotube-assembled carbon aerogel nanocomposites with high electrical conductivity

Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features.Herein,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels.After extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries.Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.

Method of fabricating artificial rock specimens based on extrusion free forming(EFF)3D printing

Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.

Use of polymer combinations in the preparation of solid dispersions of a thermally unstable drug by hot-melt extrusion

The objective of the study was to prepare solid dispersions containing a thermally unstable drug by hot-melt extrusion(HME).Carbamazepine(CBZ)was selected as model drug and combinations of Kollidon VA64(VA64),Soluplus(SOL)and Eudragit EPO(EPO)were utilized as carriers.Preformulation was conducted to identify the suitability of polymer combinations based on solubility parameters,differential scanning calorimetry(DSC),hot stage microscopy and thermogravimetric analysis.Physicochemical properties of solid dispersions were determined by DSC,X-ray diffraction,fourier transform infrared spectroscopy,dissolution and accelerated stability testing.The results show that drug-polymer miscibility at temperatures below the melting point(Tm)of CBZ was improved by combining EPO with VA64 or SOL.With 30%drug loading in a solid dispersion in SOL:EPO(1:1,w/w),CBZ was mainly present in an amorphous form accompanied by a small amount of a microcrystalline form.The dissolution rate of the solid dispersion was significantly increased(approximately 90%within 5 min)compared to either the pure drug(approximately 85%within 60 min)or the corresponding physical mixture(approximately 80%within 60 min)before and after storage.The solid dispersion in SOL:EPO(1:1,w/w)was relatively stable at 401C/75%RH under CBZ tablet packaging conditions for at least 3 months.In conclusion,polymer combinations that improve drug-polymer miscibility at an HME processing temperature below the Tm of a drug appear to be beneficial in the preparation of solid dispersions containing thermally unstable drugs.

In vitro dissolution and oral bioavailability study of fenofibrate nanomatrix system prepared by hot-melt extrusion

Solvent evaporation method for preparation of nanomatrix has the disadvantages,such as residual organic solvent,environmental pollution,explosion-proofing and so on.To overcome these shortcomings,a series of fenofibrate nanomatrix drug delivery system(NDDS)consisting of nano-porous silica Sylysia■350(S350)and pH sensitive material Eudragit■L100-55(EL100-55)were prepared using hot-melt extrusion(HME),and their in vitro dissolution and in vivo bioavailability were compared.Finally,the formulation with the highest in vivo bioavailability was selected as the optimized formulation for DSC and PXRD characterization.The results showed that the optimized NDDS showed a higher bioavailability than the reference formulation,although there was crystalline form drug remaining in NDDS.The relative bioavailability of the optimized formulation was 157.1%compared with the commercial product Lipanthyl■.In addition,the relative bioavailability of the optimized formulation was 124.8%in comparison with the formulation prepared by solvent evaporation method,showing that the NDDS prepared by the HME method was effective in improving the bioavailability of fenofibrate.In conclusion,HME was a promising method to prepare NDDS.

Designing new low alloyed Mg-RE alloys with high strength and ductility via high-speed extrusion

Two new low-alloyed Mg-2RE-0.8Mn-0.6Ca-0.5Zn(wt%,RE=Sm or Y)alloys are developed,which can be produced on an in-dustrial scale via relatively high-speed extrusion.These two alloys are not only comparable to commercial AZ31 alloy in extrudability,but also have superior mechanical properties,especially in terms of yield strength(YS).The excellent extrudability is related to less coarse second-phase particles and high initial melting point of the two as-cast alloys.The high strength-ductility mainly comes from the formation of fine grains,nano-spaced submicron/nano precipitates,and weak texture.Moreover,it is worth noting that the YS of the two alloys can maintain above 160 MPa at elevated temperature of 250°C,significantly higher than that of AZ31 alloy(YS:45 MPa).The Zn/Ca solute segregation at grain boundaries,the improved heat resistance of matrix due to addition of RE,and the high melting points of strengthening particles(Mn,MgZn_(2),and Mg-Zn-RE/Mg-Zn-RE-Ca)are mainly responsible for the excellent high-temperature 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 ℃ 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.

Difference in extrusion temperature dependences of microstructure and mechanical properties between extruded AZ61 and AZ91 alloys

The effects of extrusion temperature on the microstructure and tensile properties of extruded AZ61 and AZ91 alloys are investigated by subjecting them to hot extrusion at 300 and 400℃.Although the average grain size of the extruded AZ61 alloy slightly increases from 9.5 to 12.6μm with increasing extrusion temperature,its resultant microstructural variation is insignificant.In contrast,the average grain size of the extruded AZ91 alloy significantly increases from 5.7 to 22.5μm with increasing extrusion temperature,and the type of Mg17Al12 precipitates formed in it changes from fine dynamic precipitates with a spherical shape to coarse static precipitates with a lamellar structure.As the extrusion temperature increases,the tensile yield strength of the extruded AZ61 alloy increases from 183 to 197 MPa while that of the extruded AZ91 alloy decreases from 232 to 224 MPa.The tensile elongations of the extruded AZ61 and AZ91 alloys decrease with increasing extrusion temperature,but the degree of decrease is significant in the latter alloy.These different extrusion temperature dependences of the tensile properties of the extruded AZ61 and AZ91 alloys are discussed in terms of their microstructural characteristics,strengthening mechanisms,and crack initiation sites.

Mechanism of plasticity enhancement of AZ31B magnesium alloy sheet by accumulative alternating back extrusion

Accumulative alternating back extrusion was a potential fine-grain modification method.In this paper,it was an innovative attempt to develop high-performance magnesium alloy sheet by this process.Under the condition of 350 K,commercial AZ31 magnesium alloy was made into billet by accumulative alternating back extrusion,and then extruded into fine-grain magnesium alloy sheet.Through a systematic study of its microstructure and mechanical properties,the results showed that the initial state had an important influence on the evolution of the structure during extrusion.After accumulative alternating back extrusion to produce the billet,the grain size of the sheet obtained by extrusion was significantly refined,which was related to the accumulation of deformation and grain refinement during the alternating loading process.Grain refinement caused the proportion of dynamic recrystallization inside the sheet with 2 cycles of accumulative alternating back extrusion to drop to 27%.With the increase of extrusion cycles from 2 to 4,the high density of dislocations led to an increase in the proportion of dynamic recrystallization and finer grains.The texture changed from strong basal texture to weak bimodal texture.The results of uniaxial tensile test show that due to grain refinement and texture change,the yield strength was significantly reduced,and the plasticity was significantly improved.It was verified that accumulative alternating back extrusion was meaningful for subsequent processing,and it also provided scientific guidance for the development of fine-grained magnesium alloy sheet.

Variations in dynamic recrystallization behavior and mechanical properties of AZ31 alloy with extrusion temperature

This study investigates the effects of extrusion temperature on the dynamic recrystallization(DRX)behavior of a Mg-3Al-1Zn-0.3Mn(AZ31,wt%)alloy during hot extrusion and on the microstructural characteristics and mechanical properties of materials extruded at 350 and 450℃.An increase in the extrusion temperature causes a decrease in the amount of strain energy accumulated in the material during extrusion,because of promoted activation of pyramidal<c+a>slip and dynamic recovery.This reduced strain energy weakens the DRX behavior during extrusion,which eventually results in a decrease in the area fraction of recrystallized grains of the extruded material.The material extruded at 450℃has coarser grains and a stronger basal fiber texture than that extruded at 350℃.As the extrusion temperature increases from 350 to 450℃,the tensile yield strength(TYS)of the extruded material increases from 191.8 to 201.5 MPa,whereas its compressive yield strength(CYS)decreases from 122.5 to 111.0 MPa;consequently,its tension-compression yield stress ratio(CYS/TYS)decreases from 0.64 to 0.55.The increase in the TYS is attributed mainly to the stronger texture hardening and strain hardening effects of the extruded material,and the decrease in the CYS is attributed to the reduced twinning stress resulting from grain coarsening and texture intensification.The microstructural and textural evolutions of the materials during extrusion and the deformation and hardening mechanisms of the extruded materials are discussed in detail.

Advanced strategies in the application of gelatin-based bioink for extrusion bioprinting

The significance of bioink suitability for the extrusion bioprinting of tissue-like constructs cannot be overemphasized.Gelatin,derived from the hydrolysis of collagen,not only can mimic the extracellular matrix to immensely support cell function,but also is suitable for extrusion under certain conditions.Thus,gelatin has been recognized as a promising bioink for extrusion bioprinting.However,the development of a gelatin-based bioink with satisfactory printability and bioactivity to fabricate complex tissue-like constructs with the desired physicochemical properties and biofunctions for a specific biomedical application is still in its infancy.Therefore,in this review,we aim to comprehensively summarize the state-of-the-art methods of gelatin-based bioink application for extrusion bioprinting.Wefirstly outline the properties and requirements of gelatin-based bioinks for extrusion bioprinting,highlighting the strategies to overcome their main limitations in terms of printability,structural stability and cell viability.Then,the challenges and prospects are further discussed regarding the development of ideal gelatin-based bioinks for extrusion bioprinting to create complex tissue-like constructs with preferable physicochemical properties and biofunctions.

Simple shear extrusion versus equal channel angular pressing:A comparative study on the microstructure and mechanical properties of an Mg alloy

Two severe plastic deformation(SPD)techniques of simple shear extrusion(SSE)and equal channel angular pressing(ECAP)were employed to process an extruded Mg-6Gd-3Y-1.5Ag(wt%)alloy at 553 K for 1,2,4 and 6 passes.The microstructural evolutions were studied by electron back scattered diffraction(EBSD)analysis and transmission electron microscopy(TEM).The initial grain size of 7.5μm in the extruded alloy was reduced to about 1.3μm after 6 SPD passes.Discontinuous dynamic recrystallization was suggested to be operative in both SSE and ECAP,with also a potential contribution of continuous dynamic recrystallization at the early stages of deformation.The difference in the shear strain paths of the two SPD techniques caused different progression rate of dynamic recrystallization(DRX),so that the alloys processed by ECAP exhibited higher fractions of recrystallization and high angle grain boundaries(HAGBs).It was revealed that crystallographic texture was also significantly influenced by the difference in the strain paths of the two SPD methods,where dissimilar basal plane texture components were obtained.The compression tests,performed along extrusion direction(ED),indicated that the compressive yield stress(CYS)and ultimate compressive strength(UCS)of the alloys after both SEE and ECAP augmented continuously by increasing the number of passes.ECAP-processed alloys had lower values of CYS and UCS compared to their counterparts processed by SSE.This difference in the mechanical responses was attributed to the different configurations of basal planes with respect to the loading direction(ED)of each SPD technique.

Bimodal grain structure formation and strengthening mechanisms in Mg-Mn-Al-Ca extrusion alloys

The effects of small additions of calcium (0.1%and 0.5%~1) on the dynamic recrystallization behavior and mechanical properties of asextruded Mg-1Mn-0.5Al alloys were investigated.Calcium microalloying led to the formation of Al_(2)Ca in as-cast Mg-1Mn-0.5Al-0.1Ca alloy and both Mg_(2)Ca and Al_(2)Ca phases in Mg-1Mn-0.5Al-0.5Ca alloy.The formed Al_(2)Ca particles were fractured during extrusion process and distributed at grain boundary along extrusion direction (ED).The Mg_(2)Ca phase was dynamically precipitated during extrusion process,hindering dislocation movement and reducing dislocation accumulation in low angle grain boundaries (LAGBs) and hindering the transformation of high density of LAGBs into high angle grain boundaries (HAGBs).Therefore,a bimodal structure composed of fine dynamically recrystallized (DRXed) grains and coarse un DRXed regions was formed in Ca-microalloyed Mg-1Mn-0.5Al alloys.The bimodal structure resulted in effective hetero-deformation-induced (HDI) strengthening.Additionally,the fine grains in DRXed regions and the coarse grains in un DRXed regions and the dynamically precipitated Mg_(2)Ca phase significantly enhanced the tensile yield strength from 224 MPa in Mg-1Mn-0.5Al to335 MPa and 352 MPa in Mg-1Mn-0.5Al-0.1Ca and Mg-1Mn-0.5Al-0.5Ca,respectively.Finally,a yield point phenomenon was observed in as-extruded Mg-1Mn-0.5Al-x Ca alloys,more profound with 0.5%Ca addition,which was due to the formation of (■) extension twins in un DRXed regions.

Texture property and weakening mechanism of Mg-3Al-1Zn alloy by interactive alternating forward extrusion

The interactive alternating forward extrusion(AFE) method can realize the change of texture type and the weakening of texture strength.Taking AZ31 magnesium alloy as an example, the texture evolution of interactive AFE was studied. The results show that all kinds of dynamic recrystallization(DRX) behaviors can weaken the texture to vary degrees. The weakening effect of twinning-induced recrystallization(TDRX)behavior was particularly significant. During the interactive AFE process, the c-axis of most grains rotated under the external force, and tended to be 90° angle with the ED direction, forming a stable fiber texture. In addition, with the increase of loading passes, the starting of {0001} <11–20> basal slip system became more and more difficult. The(10–10) texture formed by {10–10} <11–20> prismatic slip system after sixth passes was the main texture type. With the increase of forming temperature, the starting ability of {10–10} <11–20>prismatic slip systems increased, and the(10–10) texture formed by prismatic slip system above 623 K dominated.

New Technology of Multidirectional Loading Rotary Extrusion

To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement, a new multidirectional loading rotary extrusion forming technology is developed to match the linear motion with the rotary motion and actively increases the strong shear force. Its principle is that the radial force and rotating torque increase when the blank is axially extruded and loaded. Through the synergistic action of axial, radial, and rotating motions, the orderly fow of metal is controlled, and the cumulative severe plastic deformation (SPD) of an“uplift-trowel” micro-area is generated. Consequently, materials are uniformly strengthened and toughened. Simultaneously, through the continuous deformation of a punch “ellipse-circle,” a high reinforcement component is grown on the cylinder wall to achieve the high-quality formation of cylindrical parts or the inner-ring-reinforcement components. Additionally, the efective strain increases with rotation speed, and the maximum intensity on the basal plane decreases as the number of revolutions increase. The punch structure also afects the axial extrusion loading and equivalent plastic strain. Thus, the proposed technology enriches the plastic forming theory and widens the application feld of plastic forming. Furthermore, the formed large-scale high-performance inner-ring-stifened magnesium components have been successfully verifed in aerospace equipment, thereby solving the problems of integral forming and severe deformation strengthening and toughening. The developed technology has good prospects for mass production and application.