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Tensile and cyclic deformation response of friction-stir-welded dissimilar aluminum alloy joints:Strain localization effect

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Journal of Materials Science & Technology 2021年第14期73卷 91-100页

作者： P.L.Niu W.Y.Li D.L.Chen State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding TechnologiesNorthwestern Polytechnical UniversityXi'an710072.China Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoOntarioM5B2K3Canada

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates,along with transmission electron microscopy examinations to characterize the precipitates required to assess internal *** backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSWed *** localization appeared in the heat affected zone(HAZ)of AA2024 *** cyclic deformation of 500 cycles at a total strain amplitude of 0.5%,the strength of the dissimilar joints resumed basically to that of AA2024 base *** the AA2024 HAZ was obviously hardened,which should be attributed to the introduced dislocations during cyclic deformation *** hardening capacity of the joints increased with decreasing strain rate.

关键词： Friction stir welding Dissimilar aluminum alloys Strain localization Cyclic hardening Slip irreversibility

De-twinning and Texture Change in an Extruded AM30 Magnesium Alloy during Compression along Normal Direction

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Journal of Materials Science & Technology 2015年第3期31卷 264-268页

作者： D.Sarker J.Friedman D.L.Chen Department of Mechanical and Industrial Engineering Ryerson University

Twinning and de-twinning are the salient deformation mechanisms in hexagonal close-packed(hcp)metals. The aim of this study was to examine and quantify the de-twinning process involving a reversible motion of twin boundaries in an extruded AM30 magnesium alloy after re-compression along the normal direction(ND) of pre-compressed samples along the extrusion direction(ED). {1012} extension twins were first introduced at a compressive strain of 3.7% along the ED. The subsequent compressive deformation along the ND induced a gradual shrinkage of twins with increasing cumulative true strain,and the complete de-twinning occurred at a strain of ~7.7%. The twin width decreased linearly with increasing true strain. Texture measurements verified the rotation of c-axes of hcp unit cells towards the anti-compression direction due to {1012} extension twinning after compression along the ED, and a gradual return of c-axes to the initial orientation due to twin shrinking or de-twinning during the following compression along the ND. The {1012} twinning corresponded to the formation of new texture components C{1210} and D{0110} and a decrease in the initial texture components A{0001} and B{0001}, while the twin shrinking or de-twinning was characterized by a gradual vanishing of components C{1210} and D{0110} and an increase in the components A{0001} and B{0001}.

关键词： Magnesium alloy Compressive deformation Twinning D

A modified Johnson-Cook constitutive relationship for a rare-earth containing magnesium alloy

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Journal of Rare Earths 2013年第12期31卷 1202-1207页

作者： F.A.Mirza 陈道伦李德江曾小勤 Department of Mechanical and Industrial Engineering Ryerson University The State Key Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong University

Lightweight magnesium alloy has recently attracted a considerable interest in the automotive and aerospace industries to improve fuel efficiency and reduce CO2 emissions via the weight reduction of ***-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through weakening crystallographic textures associated with the strong mechanical anisotropy and tension-compression yield *** the addition of RE elements sheds some light on the alteration in the mechanical anisotropy,available information on the constitutive relationships used to describe the flow behavior of RE-containing magnesium alloys is *** establish such a constitutive relationship,uniaxial compressive deformation tests were first conducted on an extruded Mg-10Gd-3Y-0.5Zr（GW103K） magnesium alloy at the strain rates ranging from 1×10–1 to 1×10–4s–1 at room temperature.A modified Johnson-Cook constitutive equation based on a recent strain hardening equation was proposed to predict the flow stresses of GW103K *** between the predicted and experimental results showed that the modified Johnson-Cook constitutive equation was able to predict the flow stresses of the RE-containing magnesium alloy fairly accurately with a standard deviation of about 1.8%.

关键词： magnesium alloy rare-earth element compression constitutive equation

Microstructure and low cycle fatigue of a Ti2AlNb-based lightweight alloy

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Journal of Materials Science & Technology 2020年第9期44卷 140-147页

作者： Yinling Zhang Aihan Feng Shoujiang Qu Jun Shen Daolun Chen School of Materials Science and Engineering Tongji UniversityShanghai 201804China Department of Mechanical and Industrial Engineering Ryerson UniversityTorontoOntario M5B 2K3Canada Shanghai Key Laboratory of D&A for Metal-Functional Materials School of Materials Science&EngineeringTongji UniversityShanghai 201804China College of Mechatronics and Control Engineering Shenzhen UniversityShenzhen 518060China

Ti2AlNb-based intermetallic compounds are considered as a new category of promising lightweight aerospace materials due to their balanced mechanical *** aim of this study was to evaluate monotonic and cyclic deformation behavior of an as-cast Ti-22A1-20Nb-2V-1Mo-0.25Si(at.%)intermetallic compound in relation to its *** alloy containing an abundant fine lamellar O-Ti2AlNb phase exhibited a good combination of strength and plasticity,and superb fatigue resistance in comparison with other intermetallic *** stabilization largely remained except slight cyclic hardening occurring at higher strain *** fatigue life could be described using the common Coffin-Mason-Basquin equation,it could be better predicted via a weighted energy-based *** crack growth was characterized mainly by crystallographic cracking,along with fatigue striationlike features being unique to appear in the *** results obtained in this study lay the foundation for the safe and durable applications of Ti2AlNb-based lightweight intermetallic compounds.

关键词： Ti2AlNb-based alloy Cyclic deformation Low cycle fatigue Fatigue life prediction Fracture

Strengthening mechanisms in magnesium alloys containing ternary Ⅰ,W and LPSO phases

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Journal of Materials Science & Technology 2018年第7期34卷 1110-1118页

作者： N.Tahreen D.F. Zhang F.S. Pan X.Q. Jiang D.Y. Li D.L. Chen Department of Mechanical and Industrial Engineering Ryerson University Toronto Ontario MSB 2K3 Canada College of Materials Science and Engineering Chongqing University Chongqing 400045 China National Engineering research Center for Magnesium Alloys Chongqing University Chongqing 400044 China Advanced Materials research Center ChongqingAcademy of Science and Technology Chongqing 401123 China Faculty of Materials and Energy Southwest University Chongqing 400715 China Department of Chemical and Materials Engineering University of Alberta Alberta T6G 11-19 Canada

This study was aimed at identifying underlying strengthening mechanisms and predicting the yield strength of as-extruded Mg-Zn-Y alloys with varying amounts of yttrium （Y） element. The addition of Y resulted in the formation of ternary 1 （Mg3YZn6）, W （Mg3Y2Zn3） and LPSO （Mg12YZn） phases which subse- quently reinforced alloys ZM31 ＋ 0.3Y, ZM31 ＋ 3.2Y and ZM31 ＋ 6Y, where the value denoted the amount of Y element （in wt%）. Yield strength of the alloys was determined via uniaxial compression testing, and grain size and second-phase particles were characterized using OM and SEM. In-situ high-temperature XRD was performed to determine the coefficient of thermal expansion （CTE）, which was derived to be 1.38 x 10^-5 K^-1 and 2.35 x 10^-5 K^-1 for W and LPSO phases, respectively. The individual strengthening effects in each material were quantified for the first time, including grain refinement, Orowan looping, thermal mismatch, dislocation density, load-bearing, and particle shearing contributions. Grain refinement was one of the major strengthening mechanisms and it was present in all the alloys studied, irrespective of the second-phase particles. Orowan looping and crE mismatch were the predominant strengthening mechanisms in the ZM31＋0.3Y and ZM31 ＋ 3.2Y alloys containing I and W phases, respectively, while load-bearing and second-phase shearing were the salient mechanisms contributing largely to the superior yield strength of the LPSO-reinforced ZM31 ＋ 6Y alloy.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： Magnesium alloy I-phase W-phase LPSO phase Strengthening mechanism

Hot Deformation and Work Hardening Behavior of an Extruded Mg–Zn–Mn–Y Alloy

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Journal of Materials Science & Technology 2015年第12期31卷 1161-1170页

作者： N.Tahreen D.F.Zhang F.S.Pan X.Q.Jiang D.Y.Li D.L.Chen Department of Mechanical and Industrial Engineering Ryerson University College of Materials Science and Engineering Chongqing University National Engineering research Center for Magnesium Alloys Chongqing University Advanced Materials research Center Chongqing Academy of Science and Technology Faculty of Materials and Energy Southwest University Department of Chemical and Materials Engineering University of Alberta

The aim of this study was to evaluate the strain hardening and hot deformation behavior of asextruded Mg-Zn-Mn （ZM31） magnesium alloy with varying Y contents （0.3, 3.2, and 6 wt%） via compression testing along the extrusion direction at room temperature, 200℃ and 300 ℃. Texture and phases were identified by X-ray diffraction. Alloy ZM31 ＋ 0.3Y consisted of a mixture of fine equiaxed grains and elon- gated grains with 1-phase （Mg3YZno）; alloy ZM31 ＋ 3.2Y contained 1-phase and W-phase （Mg3Y2Zn3）; alloy ZM31 ＋ 6Y had long-period stacking-ordered （LPSO） X-phase （Mg12YZn） and Mg24Y5 particles. With increasing Y content the basal texture became weakened significantly. While alloys ZM31 ＋ 0.3Y and ZM31 ＋ 3.2Y exhibited a skewed true stress-true stain curve with a three-stage strain hardening feature caused by the occurrence of {1072} extension twinning, the true stress-true stain curve of alloy ZM31 ＋ 6Y was normal due to the dislocation slip during compression. With increasing temperature the extent of skewness decreased. While the compressive yield stress, ultimate compressive stress, strain hardening exponent, and hardening capacity all decreased as the temperature increased, the retention of the high- temperature deformation resistance increased with increasing Y content mainly due to the presence of thermally-stable LPSO X-ohase.

关键词： Magnesium alloy Yttrium effect Temperature effect Strain hardening I and W-phase LPSO X-phase

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Theoretical & Applied Mechanics Letters 2014年第4期4卷 26-33页

作者： V.K.Patel D.L.Chen S.D.Bhole Department of Mechanical and Industrial Engineering Ryerson UniversityTorontoOntario M5B 2K3 Canada

Sound dissimilar lap joints were achieved via ultrasonic spot welding （USW）, which is a solid-state joining technique. The addition of Sn interlayer during USW effectively blocked the formation of brittle Al12Mg17 intermetallic compound in the Mg-Al dissimilar joints without interlayer, and led to the presence of a distinctive composite-like Sn and Mg2Sn eutectic structure in both Mg- Al and Mg-high strength low alloy （HSLA） steel joints. The lap shear strength of both types of dissimilar joints with a Sn interlayer was significantly higher than that of the corresponding dissimilar joints without interlayer. Failure during the tensile lap shear tests occurred mainly in the mode of cohesive failure in the Mg- Al dissimilar joints and in the mode of partial cohesive failure and partial nugget pull-out in the Mg-HSLA steel dissimilar joints.

关键词： magnesium alloy ultrasonic spot welding intennetallic compounds tin interlayer