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| 1 | Microstructure and mechanical properties of Mg-Gd-Y-Sm-Al alloy and analysis of grain refinement and strengthening mechanism显示文摘The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture. | Xiaoya Chen Quanan Li Jun Chen Limin Zhu | 2019 | Journal of Rare Earths2019，37，12： | 12 |
| 2 | Effect of grain refinement on the hydrogen embrittlement of 304 austenitic stainless steel显示文摘The effect of grain size(in the range from 4 μm to 12 μm) on the hydrogen embrittlement(HE) of 304 austenitic stainless steel(ASS) was studied. HE susceptibility result shows that HE resistance increases with grain refinement. Electron backscattered diffraction kernel average misorientation(EBSD-KAM)mapping shows that the strain localization can be mitigated by grain refinement. Hence, strain localization sites which act as highways for hydrogen diffusion and preferred crack initiation sites can be reduced along with grain refinement, leading to a high HE resistance. Meanwhile, grain size shows no influence on the strain induced martensite(SIM) transformation during the hydrogen charging slow strain tensile test(SSRT). Hence, the SIM formed during hydrogen charging SSRT is not responsible for the different HE resistance of 304 ASSs with various grain sizes. Hydrogen diffusion is supposed to be controlled by a competition between short-circuit diffusion along random grain boundary(RGB) and hydrogen trapping at dislocations, leading to a maximum hydrogen diffusion coefficient in the 304 ASS with an average grain size of 8 μm. | Y.H.Fan B.Zhang J.Q.Wang E.-H.Han W.Ke | 2019 | Journal of Materials Science & Technology2019，35，10： | 10 |
| 3 | Effect of scanning speeds on electrochemical corrosion resistance of laser cladding TC4 alloy显示文摘In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhardness variation, and impedance spectrum have been studied in comparison with the TC4 titanium alloy. The results show that the main phase of cladding coating is α-Ti, and the change of scanning speed has no obvious effect on it; therefore, the supersaturated α-Ti solid solution is formed, and the acicular α martensite is obtained. As the scanning speed increases, the microstructure of cladding coating is orthogonal basket-weave, the crystal surface spacing decreases, and the average microhardness of laser cladding TC4 alloy slightly increases. When the scanning speed increases to 10 mm/s, the microhardness is about 14.71%higher than that of the substrate, and the electrochemical corrosion resistance of laser cladding TC4 alloy is also improved,which is about 2.48 times more than the substrate. Grain refinement has a great effect on enhancing the anti-electrochemical corrosion. | 冯晓甜 雷剑波 顾宏 周圣丰 | 2019 | Chinese Physics B2019，28，2： | 10 |
| 4 | Microstructure and mechanical properties of AZ91 magnesium alloy with minor additions of Sm, Si and Ca elements显示文摘The effects of Sm, Si and Ca on the microstructure and mechanical property of AZ91 magnesium alloy were investigated by means of optical microscopy (OM), differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), X-ray diffraction (XRD) and tensile testing. The results indicated that the addition of 1.5 wt.% Sm with or without 0.8 Si/Ca led to a decrease in the volume fraction of the β-Mg17Al12 phase and the formation of the intermetallic compounds of Al-Sm, Mg2Si, MgAlCa and Al2Ca. The microstructure of AZ91 alloy was significantly refined and distribution became discrete with additions of Sm and Ca;the average grain size of the α-Mg matrix was reduced from 239.7 ± 16.9 μm to 66.34 ± 5.10 μm. The AZ91-Sm-Ca alloy exhibited a good combination of yield strength at 135 MPa, ultimate tensile strength at 199 MPa and elongation at 4.32%, which was ascribed to grain refinement strengthening. Furthermore, the T6 treated AZ91-Sm-Ca alloy possessed yield strength of 154 MPa and elongation of 7.1%, which was due to grain refinement strengthening and reduction in discontinuous precipitates. | Redeemina Comfort Bonnah Yu Fu Hai Hao | 2019 | China Foundry2019，16，5： | 9 |
| 5 | An improved process for grain refinement of large 2219 Al alloy rings and its influence on mechanical properties显示文摘The large 2219 Al alloy rings used to connect propellant tank components of a satellite launch vehicle to each other are conventionally manufactured by radial-axial ring rolling at 460°C with 50% deformation,but often suffer from coarse elongated grain and low ductility. An improved process(hot ring rolling at460°C with 30% deformation, then air cooling to 240°C, followed by ring rolling at 240°C with 20% deformation) was tested for ring manufacturing. The corresponding microstructure evolution and mechanical properties of the produced rings were studied. The results show that the improved process can successfully be applied to manufacture the large 2219 Al alloy rings without formation of macroscopic defects,resulting in a product with fine and uniform grains after heat treatment. The fracture mechanism of both rings was mainly intergranular fracture. With the resulting grain size refinement due to the improved process, more homogeneous slip occured and the crack propagation path became more tortuous during the tensile testing process. Thus, the elongation in all three orthogonal directions was greatly improved,and the axial elongation increased from 3.5% to 10.0%. | Hailin He Youping Yi Shiquan Huang Yuxun Zhang | 2019 | Journal of Materials Science & Technology2019，35，1： | 9 |
| 6 | Effect of Ce on the cleanliness, microstructure and mechanical properties of high strength low alloy steel Q690E in industrial production process显示文摘In order to improve the strength and toughness of Q690 E steel sheets,the effect of rare earth element Ce on the strength and toughness of Q690 E steel was studied by means of transmission electron microscopy,scanning electron microscopy,and metallographic microscope.The results showed that the addition of Ce in steel limited the combination of S with Mn and Ca,transformed Al2O3 inclusion into spherical CeAlO3 inclusion,and modified the precipitate form of some composite inclusions of TiN and sulfide oxides into TiN precipitation alone.The inclusions were spheroidizing.The size of inclusions was decreased from 3–5μm to 1–2μm,and the distribution was dispersed.Ce played a role in purifying molten steel through desulphurization and deoxidization.Meanwhile,the addition of Ce in steel effectively increased the nucleation particles in the liquid phase,improved the nucleation rate,enlarged the equiaxed grain refinement area,and limited the development of columnar crystals.The average grain size of slab decreased from 45.76 to 35.25μm,and the proportion of large grain size(>50μm)decreased from 40.41%to 23.74%.The macrostructural examination of slab was improved from B0.5 to C2.0,which realized the refinement of the solidified structure and reduced the banded structure of hot rolled plate.In addition,due to the inheritance of refined structure in the upstream,the recrystallization of deformed austenite and the growth of grain after recrystallization were restrained,and a refined tempered sorbite structure was obtained.When rare earth element Ce was added,the width of the martensite lath bundle was narrowed from about 500 nm to about 200 nm,which realized a remarkable grain refinement strengthening and toughening effect.Mechanical properties such as tensile,yield,and low-temperature impact toughness were significantly improved. | Hao Wang Yan-ping Bao Ming Zhao Min Wang Xiao-ming Yuan Shuai Gao | 2019 | International Journal of Minerals,Metallurgy and Materials2019，26，11： | 7 |
| 7 | Effect of the simultaneous application of a high static magnetic field and a low alternating current on grain structure and grain boundary of pure aluminum显示文摘Effect of the simultaneous application of a high static magnetic field and a low alternating electric current on the solidification structure of pure aluminum has been investigated. Results show that the refinement of the solidification structure is enhanced by the electric current under a certain magnetic field. However,when the magnetic field intensity exceeds a certain value, the refinement is impaired under a certain electric current. The observation by electron backscattered diffraction(EBSD) shows the complex fields have led to the increase of the low angle boundaries with the refinement. Moreover, the application of the static gradient magnetic field is capable of modifying the distribution of the refined grains. The above results may be attributed to the formation of the cavities during the electromagnetic vibration process and the high magnetic field. | Chengshuai Li Shaodong Hu Zhongming Ren Yves Fautrelle Xi Li | 2018 | Journal of Materials Science & Technology2018，34，12： | 7 |
| 8 | Microstructure refinement and work hardening in a machined surface layer induced by turning Inconel 718 super alloy显示文摘The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used.In this work,multiscale metallurgical observations using scanning electron microscopy,electron-backscatter diffraction microscopy,and transmission electron microscopy were conducted to quantitatively characterize the microstructure of the machined subsurface.Next,to elucidate the factors that affect the formation of the refinement microstructure,the distributions of the deformation parameters(strain,strain rate,and temperature) in the machined subsurface were analyzed.A dislocation–twin interaction dynamic recrystallization mechanism for grain refinement during machining of Inconel 718 is proposed.Furthermore,microhardness evolution induced by grain refinement in the machined surface is evaluated.The results suggest that the gradient microstructure and the work hardening can be optimized by controlling the cutting parameters during turning of Inconel 718. | Xiao-ping Ren Zhan-qiang Liu | 2018 | International Journal of Minerals,Metallurgy and Materials2018，25，8： | 7 |
| 9 | Surface grain refinement mechanism of SMA490BW steel cross joints by ultrasonic impact treatment显示文摘Ultrasonic impact treatment(UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe,which is considered as the main reason for the improvement of fatigue strength. In this paper,the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy(TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer,resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490 BW welded joints is related to the high density of dislocation tangles and dislocation walls. | Bo-lin He Lei Xiong Ming-ming Jiang Ying-xia Yu Li Li | 2017 | International Journal of Minerals,Metallurgy and Materials2017，24，4： | 6 |
| 10 | Microstructural evolution of aluminum alloy during friction stir welding under different tool rotation rates and cooling conditions显示文摘The microstructural evolution during friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the 'take-action' technique to freeze the microstructure of an Al-Mg-Si alloy during FSW, and then systematically investigated the microstructures along the material flow path under different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(DRV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(DRX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the DRX mechanisms were related to continuous DRX associated with subgrain rotation and geometric DRX at high and low rotation rates, respectively. Under the water cooling condition, we found a new DRX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase particles.Based on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of DRV and DRX was the efficient method to refine the grains during FSW. Besides, ultra-high strain rate and a short duration at high temperatures were the key factors to produce an ultrafine-grained material. | X.H. Zeng P. Xue L.H. Wu D.R. Ni B.L. Xiao K.S. Wang Z.Y. Ma | 2019 | Journal of Materials Science & Technology2019，35，6： | 6 |
| 11 | Evolution of secondary phase particles during deformation of Al-5Ti-1B master alloy and their effect on α-Al grain refinement显示文摘Addition of Al-5Ti-1B alloy to molten aluminum alloys can refine α-Al grains effectively and thereby improve their strength and toughness. TiAl_3 and TiB_2 in Al-5Ti-1B alloy are the main secondary-phase particles for refinement, while the understanding on the effect of their sizes on α-Al grain refinement continues to be fragmented. Therefore, Al-5Ti-1B alloys with various sizes and morphologies of the secondary-phase particles were prepared by equal channel angular pressing(ECAP). Evolution of the secondary-phase particles during ECAP process and their impact on α-Al grain refinement were studied by X-ray diffraction and scanning electron microscope(SEM). Results show that during the ECAP process, micro-cracks firstly appeared inside TiAl_3 particles and then gradually expanded, which resulted in continuous refinement of TiAl_3 particles. In addition, micro-distribution uniformity of TiB_2 particles was improved due to the impingement of TiAl_3 particles to TiB_2 clusters during deformation. Excessively large sizes of TiAl_3 particles would reduce the number of effective heterogeneous nucleus and thus resulted in poor grain refinement effectiveness. Moreover, excessively small TiAl_3 particles would reduce inhibitory factors for grain growth Q and weaken grain refinement effectiveness. Therefore, an optimal size range of 18-22 μm for TiAl_3 particles was suggested. | Hong Yu Ning Wang Renguo Guan Di Tie Zheng Li Yanan An Yang Zhang | 2018 | Journal of Materials Science & Technology2018，34，12： | 6 |
| 12 | Microstructure Refinement of Mg-Gd-Y-Zr Alloy Under Pulsed Magnetic Field显示文摘The effects of pulsed magnetic field on the solidified microstructure of Mg-Gd-Y-Zr alloy were investigated.Fine uniform equiaxed grains are acquired in the whole ingot by the pulsed magnetic field treatment,and the average grain size of the as-castφ50 mm and 100φmm ingots is refined to 37μm and 47μm with the pulsed magnetic field.The macrosegregation of solute elements of Mg-Gd-Y-Zr alloy is also reduced by the pulsed magnetic field treatment.Structure refinement is due to the electromagnetic undercooling zone in front of the solid/liquid interface by the magnetic pressure,and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field,which increases the nucleation rate and prohibits dendrite growth.In addition,primaryα-Mg dendrites break into fine crystals,resulting in a refined solidification structure of the magnesium alloys.The Joule heat effect induced in the melt also strengthens the grain refinement effect and the spheroidization of dendrite arms. | WANG Bin YANG Yuan-sheng | 2012 | Journal of Iron and Steel Research(International)2012，19，S1： | 6 |
| 13 | Effect of grain refinement and crystallographic texture produced by friction stir processing on the biodegradation behavior of a Mg-Nd-Zn alloy显示文摘The application of a single pass of friction stir processing(FSP) to Mg-Nd-Zn alloy resulted in grain refinement, texture evolution and redistribution of second phases, which improved corrosion resistance.In this work, an as-rolled Mg-Nd-Zn alloy was subjected to FSP. The microstructure in the processed zone of the FS-400 rpm alloy exhibited refined grains, a more homogenous grain size distribution, less second phases, and stronger basal plane texture. The corrosion behavior assessed using immersion tests and electrochemical tests in Hank’s solution indicated that the FS-400 rpm alloy had a lower corrosion rate, which was attributed to the increase of basal plane intensity and grain refinement. The hardness was lowered slightly and the elongation was increased, which might be attributed to the redistribution of the crushed second phases. | Wen Zhang Lili Tan Dingrui Ni Junxiu Chen Ying-Chao Zhao Long Liu Cijun Shuai Ke Yang Andrej Atrens Ming-Chun Zhao | 2019 | Journal of Materials Science & Technology2019，35，5： | 6 |
| 14 | Microstructure and Texture Evolution During the Direct Extrusion and Bending–Shear Deformation of AZ31 Magnesium Alloy显示文摘AZ31 alloys were extruded by direct extrusion and bending–shear deformation(DEBS).The microstructure characteristic and texture evolution of DEBSed AZ31 sheets were investigated by electron backscattered diffraction(EBSD).It is found that DEBS technique could effectively refine grains and weaken texture.Besides,we also investigate how twinning affects dynamic recrystallization during hot extrusion.{10–12}extension twins can offer nucleation sites and enough energy to trigger dynamic recrystallization.Moreover,the character of direct extrusion and bending–shear die can lead to the activation of non-basal slip system and further dramatically weaken the basal texture of the microstructure with many preactivated basal slip systems. | Xiao-Ye Liu Li-Wei Lu Kun Sheng Tao Zhou | 2019 | Acta Metallurgica Sinica(English Letters)2019，32，6： | 5 |
| 15 | Effects of Sc and Zr microalloying on the microstructure and mechanical properties of high Cu content 7xxx Al alloy显示文摘The effects of Sc and Zr microalloying on the microstructure and mechanical properties of a 7xxx Al alloy with high Cu content(7055)during casting,deformation,and heat treatment were investigated.The addition of Sc and Zr not only refined the grains but also transformed theθ-phase into the W-phase in the 7055 alloy.Minor Sc and Zr additions enhanced the hardness and yield strength of the 7055-T6 alloy by strengthening the grain boundaries and Al3(Sc,Zr)precipitates.However,a further increase in the Sc and Zr fractions did not refine the grains but instead resulted in the formation of the large-sized W-phase and primary coarse Al3(Sc,Zr)phase and subsequently deteriorated the mechanical properties of the alloys.The 7055 alloy with 0.25Sc addition exhibited the best mechanical property among the prepared alloys. | Chong-yu Liu Guang-biao Teng Zong-yi Ma Li-li Wei Bing Zhang Yong Chen | 2019 | International Journal of Minerals,Metallurgy and Materials2019，26，12： | 5 |
| 16 | Effect of refinement of grains and icosahedral phase on hot compressive deformation and processing maps of Mg-Zn-Y magnesium alloys with different volume fractions of icosahedral phase显示文摘The effect of the volume fraction of I-phase on the hot compressive behavior and processing maps of the extruded Mg-Zn-Y alloys was examined, and the obtained results were compared with those of the cast alloys in a previous work. The average grain sizes, fractions of dynamically recrystallized(DRXed) grains,and sizes of DRXed grains of the extruded alloys after compressive deformation were significantly smaller,higher and smaller, respectively, than those of the cast alloys after compressive deformation under the same experimental conditions. This was because the microstructures of the extruded alloys, having much more grain boundaries and more refined I-phase particles than the cast alloys, provided a larger number of nucleation sites for dynamic recrystallization than those of the cast alloys. The constitutive equations for high-temperature deformation of the extruded and cast alloys could be derived using the same activation energy for plastic flow, which was close to the activation energy for lattice diffusion in magnesium.Compared with the cast alloys, the onset of the power law breakdown(PLB) occurred at larger ZenerHolloman(Z) parameter values in the extruded alloys. This was because the extruded alloys had finer initial grain sizes and higher fractions of finer DRXed grains compared to the cast alloys, such that the onset of PLB caused by creation of excessive concentrations of deformation-induced vacancies was delayed to a higher strain rate and a lower temperature. The flow-stress difference between the extruded alloys and the cast alloys could be attributed to the difference in the fraction of DRXed grains. According to the processing maps, the extruded alloys exhibited higher power dissipation efficiency and flow stability than the cast alloys. This agreed with the microstructural observations. | T.Y.Kwak W.J.Kim | 2019 | Journal of Materials Science & Technology2019，35，1： | 4 |
| 17 | Effect of Sr on microstructure and aging behavior of Mg-14Li alloys | Bin Jiang a,b,c,Ying Zeng b,Hengmei Yin a,b,Ruihong Li a,b,Fusheng Pan a,b a National Engineering Research Center for Magnesium Alloys,Chongqing University,Chongqing 400030,China b College of Materials Science and Engineering,Chongqing University,Chongqing 400030,China c New Materials Center,Chongqing Academy of Science and Technology,Chongqing 401123,China | 2012 | Progress in Natural Science:Materials International2012，22，2： | 3 |
| 18 | Effect of equal channel angular pressing on aging treatment of Al-7075 alloy显示文摘The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined.Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BCat both the room temperature and 120 1C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 1C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 1C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 1C as a result of dynamic aging and formation of small η′ phase. | M.H.Shaeri M.Shaeri M.T.Salehi S.H.Seyyedein M.R.Abutalebi | 2015 | Progress in Natural Science:Materials International2015，25，2： | 2 |
| 19 | Effect of Sr addition on the grain refinement of AZ31 magnesium alloys显示文摘The grain refinement mechanisms of Sr in the AZ31 magnesium alloys were studied by both phase diagram calculation and experimental analysis.The influence of Sr content on the solute distribution coefficients of Al and Zn during solidification was investigated in order to find out whether Sr addition can enhance the grain refinement efficiency brought by Al and Zn.The results showed that Sr addition can promote the segregation in liquid phases for both Al and Zn during solidification,therefore enhance the grain refinement effects by Al and Zn in AZ31 magnesium alloys.And the effect of Sr addition on the solute distribution coefficients for Al is larger than that of Zn.Sr addition can improve the GRF values by itself and also improve the GRF values of Al and Zn to the AZ31 magnesium alloys,and the grains are refined consequently. | Renju Cheng Fusheng Pan Shan Jiang Cheng Li Bing Jiang Xianquan Jiang | 2013 | Progress in Natural Science:Materials International2013，23，1： | 2 |
| 20 | Surface nanocrystallization of Ti6AI4V induced by circulation rolling plastic deformation显示文摘A nanocrystallization surface layer was successfully obtained in a sample of Ti6Al4V. The microstructure features of the sample were characterized by using X-ray diffraction analysis(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM) observations. The average grain size in the top surface layer is about 10nm, and gradually increases with the distance from the surface increasing. | FAN Xin-min ZHU Lin HUANG Jie-wen | 2004 | 中国有色金属学会会刊:英文版2004，14，z1： | 2 |
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