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

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.Hoi extrusion refined giains 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.

Effects of Heating and Hot Extrusion Process on Microstructure and Properties of Inconel 625 Alloy

The effects of the heating process and hot extrusion on the microstructure and properties of inconel 625 alloy were studied. The experimental results showed that the properties of Inconel 625 alloy could be improved through the heating process and hot extrusion concomitant with a reduced corrosion rate. The M23C6 carbide, generated in the heating process, was retained and distributed at the grain boundary during the process of hot extrusion, which had an important influence on both elongation and corrosion resistance. The improvement of the comprehensive properties of the material, as measured by a tensile test at room temperature, was correlated with the dissolution of segregation Nb. A typical ductile fracture changed to a cleavage fracture where secondary cracks could be clearly seen. With the increase of the extrusion ratio, the real extrusion temperature was higher, which led to more dissolution of the M23C6 carbide, decreased the number of secondary cracks, enhanced the effect of solid solution strengthening, and reduced the intergranular corrosion rate. Under the condition of a high extrusion ratio and a high extrusion speed, the less extrusion time made it possible to obtain organization with a smaller average grain size. Moreover, in this case, the M23C6 carbide and segregated Nb did not have enough time to diffuse. Thus all samples exhibited medium strengths and corrosion rates after extrusion.

Effects of the deep rolling process on the surface roughness and properties of an Al-3vol%SiC nanoparticle nanocomposite fabricated by mechanical milling and hot extrusion

Deep rolling is one of the most widely used surface mechanical treatments among several methods used to generate compressive residual stress. This process is usually used for axisymmetric components and can lead to improvements of the surface quality, dimensional accuracy, and mechanical properties. In this study, we deduced the appropriate deep rolling parameters for Al-3vol%Si C nanocomposite samples using roughness and microhardness measurements. The nanocomposite samples were fabricated using a combination of mechanical milling, cold pressing, and hot extrusion techniques. Density measurements indicated acceptable densification of the samples, with no porosity. The results of tensile tests showed that the samples are sufficiently strong for the deep rolling process and also indicated near 50% improvement of tensile strength after incorporating Si C nanoparticle reinforcements. The effects of some important rolling parameters, including the penetration depth, rotation speed, feed rate, and the number of passes, on the surface quality and microhardness were also investigated. The results demonstrated that decreasing the feed rate and increasing the number of passes can lead to greater surface hardness and lower surface roughness.

Mathematical modeling of induction heating of discard substitution block for billet hot extrusion process

A magnetic and temperature field-coupled mathematical model is proposed to calculate the induction heating process of a discard substitution block for billet hot extrusion process. The mathematical model is validated by comparing simulation results with temperature measurements recorded during physical modeling. Based on systematical analysis of calculation results, a quantitative sawtooth induction power curve was proposed to realize the aim of achieving the best distributed temperature field in the block within the shortest induction time.

Fabrication of phosphor bronze/Al two-phase material by recycling phosphor bronze chips using hot extrusion process and investigation of their microstructural and mechanical properties

Despite the existence of conventional methods for recycling chips,solid-state techniques have become popular,whereby waste metals are directly recycled into consolidated products with the desired shapes and designs.We investigated the feasibility of recycling phosphor bronze chips through a hot extrusion process using aluminum powder as a metal binder for the fabrication of a metal-fiber-reinforced aluminum matrix composite.To do so,mixtures containing 20 vol%–50 vol%of chips were prepared,cold-compacted,and extruded.The quality of the consolidated samples was evaluated by determining the density of the fabricated composites and studying their microstructures.In addition,we performed tensile and hardness tests to evaluate the mechanical properties of the fabricated composites.We also analyzed the fracture surfaces of the samples to study the fracture mechanism as a function of the volume fraction of phosphor bronze chips in the fabricated composite.The results indicated that the most effective consolidation occurred in the sample containing 20 vol%of chips extruded at 465℃in which the chips serve as ideal fibers for improving the mechanical properties,especially the ultimate tensile strength,in comparison with those of Al matrixes that contain no chips but are produced under the same conditions.

Accelerating matrix/boundary precipitations to explore high-strength and high-ductile Co_(34)Cr_(32)Ni_(27)Al_(3.5)Ti_(3.5) multicomponent alloys through hot extrusion and annealing

Annealing-regulated precipitation strengthening combined with cold-working is one of the most efficient strategies for resolving the conflict between strength and ductility in metals and alloys.However,precipitation control and grain refinement are mutually contradictory due to the excellent phase stability of multicomponent alloys.This work utilizes the high-temperature extrusion and annealing to optimize the microstructures and mechanical properties of the Co_(34)Cr_(32)Ni_(27)Al_(3.5)Ti_(3.5) multicomponent alloy.Hot extrusion effectively reduces grain sizes and simultaneously accelerates the precipitation of coherent L12 nanoparticles inside the face-centered cubic(FCC)matrix and grain boundary precipitations(i.e.,submicron Cr-rich particles and L12-Ni 3(Ti,Al)precipitates),resulting in strongly reciprocal interaction between dislocation slip and hierarchical-scale precipitates.Subsequent annealing regulates grain sizes,dislocations,twins,and precipitates,further allowing to tailor mechanical properties.The high yield strength is attributed to the coupled precipitation strengthening effects from nanoscale coherent L12 particles inside grains and submicron grain boundary precipitates under the support of pre-existing dislocations.The excellent ductility results from the synergistic activation of dislocations,stacking faults,and twins during plastic deformation.The present study provides a promising approach for regulat-ing microstructures,especially defects,and enhancing the mechanical properties of multicomponent alloys.

Hot Extrusion Process Effect on Mechanical Behavior of Stir Cast Al Based Composites Reinforced with Mechanically Milled B_4C Nanoparticles

In this study, aluminum alloy （Al-2 wt% Cu） matrix composites reinforced with I, 2 and 4 wt% boron carbide nanoparticles fabricated through mechanical milling with average size of 100 nm were fabricated via stir casting method at 850℃. Cast ingots of the matrix alloy and the composites were extruded at 500℃ at an extrusion ratio of 10：1 to investigate the effects of hot extrusion on the mechanical properties of the composites. The microstructures of the as-cast and the extruded composites were investigated by scanning electron microscopy （SEM）. Density measurement, hardness and tensile tests were carried out to identify the mechanical properties of the composites. The extruded samples revealed a more uniform distribution of B4C nanoparticles. Also, the extruded samples had strength and ductility values superior to those of the as-cast counterparts. In the as-cast and the extruded samples, with increasing amount of B4C nanoparticles, yield strength and tensile strength increased but e^ongation to fracture decreased.

Effect of Si Content on Dynamic Recrystallization of Al-Si-Mg Alloys During Hot Extrusion

By using electron backscatter diffraction（EBSD） and transmission electron microscopy（TEM）, the effect of Si content on microstructure characteristics of three as-extruded Ale SieM g alloys was investigated. Results showed that the density of coarse Si particles played a critical role in dynamic recrystallization. Dynamic recrystallization rarely occurred in S1 alloy with less Si content; however, it happened in the Si-rich zones in S2 alloy with a medium Si content. And a mature recrystallization was observed in S3 alloy with high Si content. Although deformation was carried out at high temperature, particle-stimulated dynamic recrystallization occurred in Si-rich zones.

High-content graphene nanoplatelet reinforced aluminum composites produced by ball milling and hot extrusion

Due to the high specific surface area of graphene,the effective incorporation of high-content graphene in metals is challenging.Here,aluminum composites with graphene nanoplatelet(GNP)content up to 5.0 vol%were prepared by spark plasma sintering(SPS)of blended powders with various ball milling regimes and subsequent hot extrusion.The effects of GNP distribution state on the properties of GNP/Al composite were investigated.5.0 vol%GNPs were uniformly dispersed in aluminum matrix by high-speed ball milling(HSBM)process,but with damage GNPs due to the too high energy input.By contrast,the wellstructured and dispersed GNPs in aluminum powders were obtained via shift-speed ball milling(SSBM).The clear GNP-Al interface in extruded SSBM composite was attributed to well-structured GNPs.As a result,the yield strength(YS)and ultimate tensile strength(UTS)of composite produced by SSBM reached 279 and 303 MPa,which are 166%and 116%higher than those of monolithic Al.This demonstrated that it may be promising to introduce high-content GNPs with tailorable interface in Al alloys via modified ball milling technique and hot extrusion.

Microstructural evolution of spray-formed Al-11.5Zn-2.0Mg-1.6Cu alloy during hot-extrusion and heat-treatment

Al-11.5Zn-2.0Mg-1.6Cu alloy was synthesized by spray forming(SF)technique followed by hot extrusion and heat-treatment.Its microstructural evolution was investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM)with energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD)in the whole process.The curve of hardness as a function of aging time was obtained at 120℃.Test results indicate that the grain morphology is equiaxed and uniform in the central region of the spray-formed billet,but fine and irregular in the bottom and top regions.Both the grain boundary and the intragranular phases are identified as MgZn_(2) intermetallics.Hot extrusion promotes the refinement of the microstructure.Grain boundary phase disappears,meanwhile,η-phase(MgZn_(2))and Al_(3)Zr particles precipitate from the matrix after extrusion.The alloy reaches its maximum hardness after being aged at 120℃for 14 h,associated with a massive precipitation of intermediateη′-phase (MgZn)in the matrix.

Fabrication of high strength carbon nanotube/7055Al composite by powder metallurgy combined with subsequent hot extrusion

Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.

Structural and Mechanical Properties of Al/B_4C Composites Fabricated by Wet Attrition Milling and Hot Extrusion

In this study, Al matrix composites reinforced by 7.5 and 15 vol.% B4C particles and also monolithic Al （Al without the B4C particles） were produced by wet attrition milling and subsequent hot forward extrusion processes. The microstructure of the composites, evaluated by scanning electron microscopy （SEM）, showed that the B4C particles were properly distributed in the Al matrix. Mechanical properties of the Al/B4C composites and monolithic Al were investigated by tensile, wear and hardness tests, The results revealed that with increasing content of B4C particles, the tensile strength and microhardness of composites increased but the elongation decreased. In addition, the tensile strength and microhardness of composite samples were higher than those of monolithic Al. The density measurements revealed that the density of composites decreased with increasing content of the B4C particles.

Aging Behavior of Nano-SiC/2014Al Composite Fabricated by Powder Metallurgy and Hot Extrusion Techniques

The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.

Mechanical Properties of Al/BN Nanocomposites Fabricated by Planetary Ball Milling and Conventional Hot Extrusion

In this study,Al matrix nanocomposites containing 1,2 and 4 wt% nano-boron nitride were fabricated by mechanical milling and hot extrusion.The mechanical properties of all extruded samples were evaluated.Also,the morphology and microstructure of the milled composite powders were characterized using two types of electron micro-scope.The results showed that a high fraction of the boron nitride nanoparticles dissolved and formed a solid solution in Al matrix during the milling process.Through the process of solid solution formation,the work hardening rate of the composite powders increased.This led to a morphological change in the composite powders and resulted in equiaxed shape.The powder particle size also decreased after the milling process.By increasing boron nitride content within a range of 0--4 wt% in the hot extruded samples,tensile stress increased from 212 to 333 MPa.The hardness of the nanocomposite samples including 1,2 and 4 wt% boron nitride improved approximately 55,70 and 90% in comparison with pure Al,respectively.

Microstructures and mechanical properties of AZ31-0.1Ca magnesium alloy produced by soft-contact electromagnetic casting and hot extrusion

An AZ31-0.1Ca magnesium alloy produced by Soft-contact electromagnetic continuous casting （SEMC） was investigated. The fine homogeneous structure and the precipitated phases were obtained by SEMC. The effects of microalloying of Ca and middle frequency electromagnetic field on AZ31-0.1Ca magnesium alloy were discussed. And the as-cast billets were extruded with different extrusion ratios subsequently. The alloy showed an ultrafine grain size of 2-5 #m due to dynamic recrytallization （DRX） in the course of hot extrusion. The comprehensive properties of the as-extruded alloy are the best at the extrusion ratio of 25, and the hardness, UTS and elongation are 73.9 HB, 356.8 MPa and 16.570, respectively.

Stress Analysis and Optimum Design of Hot Extrusion Dies

A three-dimensional model of a hot extrusion die was developed by using ANSYS software and its second development language—ANSYS parametric design language. A finite element analysis and op-timum design were carried out. The three-dimensional stress diagram shows that the stress concentration is rather severe in the bridge of the hot extrusion die, and that the stress distribution is very uneven. The opti-mum dimensions are obtained. The results show that the optimum height of the extrusion die is 89.596 mm. The optimum radii of diffluence holes are 65.048 mm and 80.065 mm. The stress concentration is reduced by 27%.

Hot deformation behavior and microstructure evolution of Be/2024Al composites

The high temperature compression test of Be/2024Al composites with 62wt%Be was conducted at 500–575℃ and strain rate of0.003–0.1 s^(-1).The strain-compensated Arrhenius model and modified Johnson–Cook model were introduced to predict the hot deformation behavior of Be/2024Al composites.The result shows that the activation energy of Be/2024Al composites was 363.364 k J·mol^(-1).Compared with composites reinforced with traditional ceramics,Be/2024Al composites can be deformed with ultra-high content of reinforcement,attributing to the deformable property of Be particles.The average relative error of the two models shows that modified Johnson–Cook model was more suitable for low temperature condition while strain-compensated Arrhenius model was more suitable for high temperature condition.The processing map was generated and a hot extrusion experiment was conducted according to the map.A comparation of the microstructure of Be/2024Al composites before and after extrusion shows that the Be particle deformed coordinately with the matrix and elongated at the extrusion direction.

Development and evaluation of lafutidine solid dispersion via hot melt extrusion:Investigating drug-polymer miscibility with advanced characterisation

In current study,immediate release solid dispersion(SD)formulation of antiulcer drug lafutidine(LAFT)was developed using hot melt extrusion(HME)technique.Amphiphilic Soluplus
used as a primary solubilizing agent,with different concentrations of selected surfactants like PEG 400,Lutrol F127(LF127),Lutrol F68(LF68)were used to investigate their influence on formulations processing via HME.Prepared amorphous glassy solid dispersion was found to be thermodynamically and physicochemically stable.On the contrary,traces of crystalline LAFT not observed in the extrudates according to differential scanning calorimetry(DSC),X-ray diffraction(XRD),scanning electron microscopy(SEM)and Raman spectroscopy.Raman micro spectrometry had the lowest detection limit of LAFT crystals compared with XRD and DSC.Atomic Force microscopy(AFM)studies revealed drugpolymer molecular miscibility and surface interaction at micro level.1HeCOSY NMR spectroscopy confirmed miscibility and interaction between LAFT and Soluplus
,with chemical shift drifting and line broadening.MD simulation studies using computational modelling showed intermolecular interaction between molecules.Dissolution rate and solubility of LAFT was enhanced remarkably in developed SD systems.Optimized ratio of polymer and surfactants played crucial role in dissolution rate enhancement of LAFT SD.The obtained results suggested that developed LAFT has promising potential for oral delivery and might be an efficacious approach for enhancing the therapeutic potential of LAFT.

Hot Hydrostatic Extrusion of Mechanically Alloyed Al-4.9Fe-4.9Ni Powders

Al-4.9 Fe-4.9 Ni alloy powders have been synthesized by mechanical alloying. The rnechanically alloyed powders are consolidated by hot hydrostatic extrusion. The results show that extrusion tempereture. extrusion ratio and lubricant have great effects on the quality of extruded rods and their mechanical properties, The mixture of graphite and glass powders as lubricant can prevent the oxidization of cold compacted billet by cladding the billet with this lubricant before heating. This technique greatly simplifies the conventional densification process of powders