Cyclic Extrusion And Compression Research Articles

Damping performance of SiC nanoparticles reinforced magnesium matrix composites processed by cyclic extrusion and compression

This work dealt with the damping performance and its underlying mechanism in SiC nanoparticles reinforced AZ91D composite (SiCnp/AZ91D) processed by cyclic extrusion and compression (CEC). It was found that the CEC process significantly affects the damping performance of the composite due to alterations in the density of dislocations and grain boundaries in the matrix alloy. Although there would be dynamic precipitation of the Mg17Al12 phase during processing which increases the phase interface and limits the mobility of dislocations and grain boundaries. The results also showed that the damping capacity of 1%SiCnp/AZ91D composite continuously decreases with adding CEC pass number and it consistently increases with rising the applied temperature. Considering the first derivative of the tanδ–T curve, the dominant damping mechanism based on test temperature can be divided into three regions. These three regions are as follows (i) dislocation vibration of the weak pinning points (≤Tcr), (ii) dislocation vibration of the strong pinning points (Tcr∼TV), and (iii) grain boundary/interface sliding (≥TV).

Tribological Behavior of Carbon Nanotube-Reinforced AZ91D Composites Processed by Cyclic Extrusion and Compression

Reciprocating wear tests were conducted to assess the wear resistance of CNT-reinforced AZ91D composites prepared by cyclic extrusion and compression (CEC). Effects of CEC, CNTs, and wear parameters on the tribological behavior of the composites were discussed. Results show that the matrix grain of the 0.5 wt% CNTs/AZ91D composites is largely refined from ~ 112 µm to 126.6 nm after eight passes of CEC. Accordingly, the hardness of the composites is increased by more than 82.0%. The wear rate of the CNTs/AZ91D composites decreases with the implement of CEC and the addition of CNTs. The lubrication effect of CNTs diminishes after CEC. Besides the reinforcing effect, the incorporated CNTs help to liberate the friction heat of the CNTs/AZ91D composites and reduce the welding of the wear debris due to their extraordinary thermal conductivity.

Effects of Texture and Grain Size on the Yield Strength of ZK61 Alloy Rods Processed by Cyclic Extrusion and Compression.

The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation.

Strengthening and toughening mechanisms of an ultrafine grained Mg-Gd-Y-Zr alloy processed by cyclic extrusion and compression

Cyclic extrusion and compression (CEC) was implemented to process the Mg-Gd-Y-Zr alloy. Microstructure characters, including the matrix grain, precipitates and texture evolution, were tried to correlate with the mechanical performance of the post-processed alloy. Results show that after 14 passes of CEC, the average grain size of GW102K is greatly refined to ~100–200nm. Secondary-phase particles are broken due to the occurrence of tension tearing and shearing fracture. Quantitative texture analysis elucidates that CEC weakens the initial fiber texture of the extruded GW102K. Unlike most of the severe plastic deformed Mg alloys, the CEC processed GW102K alloy follows the normal Hall-Petch equation, which is closely associated with the disintegrated texture as well as the nanoscale second-phase particles. A considerable increase in elongation is witnessed and the introducing of rare-earth elements (RE) is found to change the deformation mechanisms of the Mg alloy by facilitating non-basal slip systems, twinning and shear bands.

Microstructure and mechanical properties of the carbon nanotubes reinforced AZ91D magnesium matrix composites processed by cyclic extrusion and compression

Cyclic extrusion and compression (CEC) was taken to process the carbon nanotubes (CNTs) reinforced AZ91D composites. Effects of CEC passes and CNTs on the microstructure evolution, hardness and tensile properties of the post-processed composites were investigated. Results show that the matrix grain of the 0.5wt% CNTs/AZ91D composites is greatly refined from ~112 μm to ~126.6nm after 8 passes of CEC, with Mg17Al12 uniformly distributed along grain boundaries. The addition of CNTs leads to a reduced matrix grain, but exerts a limited effect on the Mg17Al12 precipitates. The initial highly-agglomerated CNTs are gradually dispersed with the progress of CEC, though degrading of CNTs occurs. The implement of CEC markedly enhances the hardness, YS, UTS and elongation to fracture of both the monolithic AZ91D alloy and the CNTs/AZ91D composites, all of which are mainly attributed to the greatly refined matrix grain and the uniformly distributed Mg17Al12 precipitates. Incorporation of CNTs increases the hardness, YS and UTS of the base alloy, but decreases the elongation to fracture, which is closely related with the gradually dispersed but degraded CNTs.

Effects of cyclic extrusion and compression on the microstructure and mechanical properties of AZ91D magnesium composites reinforced by SiC nanoparticles

Cyclic extrusion and compression (CEC) was implemented on the SiC nanoparticles reinforced AZ91D magnesium composites at 300°C, 350°C and 400°C. Up to 8 passes were performed. Effects of CEC parameters on the microstructure and mechanical properties of the n-SiCp/AZ91D composites were investigated. Results show that fine grains appear immediately after 1 pass of CEC and invade continuously with the progress of CEC from grain boundaries and twin bands to the center of the grain. After 8 passes of CEC at 300°C, the matrix grains are effectively refined down to ~130nm, with Mg17Al12 uniformly distributed along grain boundaries. Increasing in the CEC temperature leads to an obvious growth of the matrix grain and coarsening of the Mg17Al12. Clusters of SiC nanoparticles are remarkably dispersed after 8 passes of CEC. Besides the normal extrusion component, multi-pass of CEC induces other complex texture components, which is attributed to the activation of various twinning, especially 101−2 twinning, 101−1 twinning and 101−1−101−2 double twinning. The grain refinement mechanism is verified as twinning-assisted rotational DRX accompanied by continuous DRX at relatively low temperature (<350°C). The dynamically precipitated Mg17Al12 and the incorporated SiC nanoparticles act as obstacles for the growth of the fine grains. Eventually, an increase of ~43.57% is achieved in the hardness of the n-SiCp/AZ91D composites after 8 passes of CEC at 300°C.

Effects of cyclic extrusion and compression parameters on microstructure and mechanical properties of Mg–1.50Zn–0.25Gd alloy

Abstract Mg–1.50Zn–0.25Gd (at.%) alloy reinforced by icosahedral quasicrystalline phase (I-phase) was fabricated and then subjected to cyclic extrusion and compression (CEC) at 250, 300, 350 and 400 °C, respectively. The effects of CEC parameters including passes and temperatures on microstructure evolution and room temperature tensile mechanical properties were characterized and discussed. The results show that more passes are beneficial for secondary phase precipitation, grain refinement and basal texture weakening; while moderate temperature is beneficial for secondary phase precipitation and basal texture weakening by particle stimulated recrystallization nucleation (PSN), and lower temperature is beneficial for grain refinement. The alloy has the highest yield strength after CEC at 250 °C because of grain refinement and basal texture strengthening, while it has the highest elongation after being processed with 8 passes of CEC due to grain refinement and basal texture weakening. The processing passes have more important effects on microstructure evolution and mechanical properties than that of temperature during CEC.

Microstructure evolution and mechanical properties of quasicrystal-reinforced Mg–Zn–Gd alloy processed by cyclic extrusion and compression

Mg–1.5Zn–0.25Gd (at.%) alloy reinforced by icosahedral quasicrystalline phase (I-phase) was fabricated and subjected to cyclic extrusion and compression (CEC) at 350°C to investigate the microstructure evolution during CEC and its effect on the mechanical properties. It is observed that, during CEC, the microstructure of the alloy was greatly refined by dynamic recrystallization (DRX), large numbers of I-phase particles precipitated and then grew up, the texture of the alloy was obviously weakened. These changes in microstructure improved the mechanical properties of the alloy significantly and the alloy processed by 8 passes CEC exhibited outstanding plasticity of 31.4% and moderate yield strength of 161MPa.

Microstructure Evolution in Magnesium Alloy ZK60 during Cyclic Extrusion and Compression

The microstructural evolution of of as-cast ZK60 magnesium alloy processed by cyclic extrusion and compression (CEC) were studied, and the effects of technical parameters on microstructural evolution were investigated. The results show that the grains of as-cast ZK60 magnesium alloy were obviously refined and uniformed by CEC, the average grain size was decreased from original 50 ~ 60 μm to about 2 μm when the extrusion ratio was 8 with 8-passes at 350°C, and the refinement effect was increased with the rising of extrusion ratio and passes. The effect of increasing passes on grain refinement was not obvious when it exceeds 8. Nevertheless, it is beneficial for the grain homogenization.

&lt;i&gt;In-Situ&lt;/i&gt; Study on Deformation Behavior of ZK60 Alloy Processed by Cyclic Extrusion and Compression

The effects of cyclic extrusion and compression (CEC) on the deformation behavior and failure of ZK60 alloy were examined using in-situ scanning electron microscope (SEM) uniaxial tensile testing at room temperature. Fracture surface was analyzed by SEM. Result shows that the tensile elongation of the extruded ZK60 alloy is obviously increased by CEC deformation. The change in fracture modes has been attributed to the suppression of twinning and the activation of non-basal slips due to the grain refinement and texture modification induced by CEC deformation. [doi:10.2320/matertrans.MC201405]

Influence of Grain Refinement and Texture Evolution on the Yield Strength of Mg Alloy Processed by Cyclic Extrusion and Compression

The microstructure, texture and room temperature tensile property of an extruded GW102K alloy processed by cyclic extrusion and compression (CEC) at 350°C were investigated. Results show that the microstructure was effectively refined and the initial fiber texture changed to a new texture. The strength and ductility were simultaneously increased obviously. In particular, yield strength increases with decreasing grain sizes, and exhibiting clear grain size dependency according to Hall­Petch relation. The grain refines strengthening is the largest contributor to the yield strength and the texture play relatively minor roles on yield strength in CEC-processed GW102K alloy. [doi:10.2320/matertrans.MA201306]

Finite element analysis of strain distribution in ZK60 Mg alloy during cyclic extrusion and compression

Finite element method was used to study the strain distribution in ZK60 Mg alloy during multi-pass cyclic extrusion and compression (CEC). In order to optimize the CEC processing, the effects of friction condition and die geometry on the distribution of total equivalent plastic strain were investigated. The results show that the strain distributions in the workpieces are inhomogeneous after CEC deformation. The strains of the both ends of the workpieces are lower than that of the center region. The process parameters have significant effects on the strain distribution. The friction between die and workpiece is detrimental to strain homogeneity, thus the friction should be decreased. In order to improve the strain homogeneity, a large corner radius and a low extrusion angle should be used.

Mechanical properties and biocorrosion resistance of Mg-Nd-Zn-Zr alloy improved by cyclic extrusion and compression

Mg-Nd-Zn-Zr alloy is a promising biodegradable magnesium alloy due to higher mechanical properties and better corrosion resistance than commercial AZ31 and WE43 alloys. However, the mechanical properties and the corrosion resistance of the alloy should be further improved to meet the requirement of clinical application. In this study, cyclic extrusion and compression (CEC) processing was adopted to refine grains of Mg-Nd-Zn-Zr alloy. Mechanical properties and biocorrosion resistance of the alloy were evaluated. The results show that the yield strength, ultimate tensile strength and elongation of the alloy under CEC processing has ~71%, ~28% and ~154% improvement, respectively. The biocorrosion resistance of the alloy under CEC processing was also improved apparently.

Microstructure and Mechanical Properties of Mg-3Y Binary Alloy Processed by Cyclic Extrusion and Compression

Mg-3wt.%Y alloys were processed by cyclic extrusion and compression (CEC) up to 7 passes at different temperatures from 375 to 450 °C, respectively. The microstructure was effectively refined and the mean grain size was decreased from 800 μm to 3–15 μm. Tensile and compressive tests were performed at room temperature at an initial strain rate of 1.11 × 10-3 s-1. The experimental results show that after 7-pass CEC processing the tensile yield strength and elongation-to-failure of Mg-3Y alloy increased simultaneously. Furthermore, the strength differential effect (SDE) of tension-compression of the alloy was weakened, especially the SDE value was only 3.3% when processed at 400 °C.

Microstructure and texture characteristics of ZK60 Mg alloy processed by cyclic extrusion and compression

The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression (CEC) up to 8 passes at 503 K were investigated. The local crystallographic texture, grain size and distribution, and grain boundary character distributions were analyzed using high-resolution electron backscatter diffraction (EBSD). The results indicate that the microstructure is refined significantly by the CEC processing and the distributions of grain size tend to be more uniform with increasing CEC pass number. The fraction of low angle grain boundaries (LAGBs) decreases after CEC deformation, and a high fraction of high angle grain boundaries (HAGBs) is revealed after 8 passes of CEC. Moreover, the initial fiber texture becomes random during CEC processing and develops a new texture.

Microstructure and enhanced mechanical properties of an Mg–10Gd–2Y–0.5Zr alloy processed by cyclic extrusion and compression

The evolution of microstructure and texture of an extruded GW102K Mg alloy processed by cyclic extrusion and compression (CEC) at 450°C were investigated. Tensile tests were performed at room temperature and strain rate 5×10−3s−1. The results show that the microstructure was effectively refined, and the initial fiber texture became disintegrated and developed a new texture after 14 CEC passes. It was found that the strength and ductility were simultaneously increased compared with the as-extruded alloy. In particular, the elongation and yield strength were related in a line relationship having a positive slope. As the texture changed and texture intensity decreased, substantial grain refinement was observed. The hard second-phase particles were considered to be responsible for the uncommon properties of the GW102K alloy processed by CEC.

Study on deformation behavior and strain homogeneity during cyclic extrusion and compression

In this paper, the plastic deformation behavior and strain homogeneity of the ZK60 Mg alloy during the multi-pass cyclic extrusion and compression (CEC) was simulated using the finite-element method (FEM) with a view to provide an insight into the mechanics of the process. Physical modeling (PM) experiment with same alloy was carried out to verify the results of the numerical simulations. The results show that two vortex flow regions with opposite flow direction are formed inside the cylindrical workpiece during CEC deformation. Although the deformation is inhomogeneous in both end regions of workpiece, a uniform region of equivalent strain exists, and the extent of uniform deformation increased with the increase in workpiece length.

Microstructure and high tensile ductility of ZK60 magnesium alloy processed by cyclic extrusion and compression

The microstructure and texture development of an extruded ZK60 Mg alloy during cyclic extrusion and compression (CEC) at 230 °C was investigated. Tensile tests were performed at room temperature at a strain rate of 1 × 10 −3 s −1. The results show that the microstructure was effectively refined by the CEC processing. The initial fiber texture became disintegrated during CEC processing and developed a new texture. After CEC 4-passes, the elongation-to-failure significantly increased almost three times compared with that of as-extruded alloy. Texture change and grain refinement were considered to be responsible for the large tensile ductility in the CEC processed ZK60 alloy. Furthermore, the smaller intensity of texture of CEC processed specimen may be another reason for the large ductility.

Effect of the Cyclic Extrusion and Compression Processing on Microstructure and Mechanical Properties of As-Extruded ZK60 Magnesium Alloy

The effects of cyclic extrusion and compression (CEC) processing on the microstructure and mechanical properties of ZK60 Mg alloy were investigated at room temperature. ZK60 alloy was dramatically refined by CEC processing at 350°C. In addition, the initial fiber texture became disintegrated and changed into a {1013}(3032) + {1011}(1543) texture. Due to microstructure refining and texture variation, the compressive yield stress of ZK60 alloy increased remarkably while the tensile yield stress decreased slightly. As a result, the intensity of strength-differential effect (SDE) of ZK60 alloy was decreased noticeably. The ductility of ZK60 alloy also enhanced, especially under compression test condition.