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Improvement of Microstructure and Mechanical Properties of Rapid Cooling Friction Stir-welded A1050 Pure Aluminum

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Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 134-141页

作者：许楠 LIU Lutao SONG Qining ZHAO Jianhua bao yefeng College of Materials Science and Engineering Hohai UniversityChangzhou 213200China

Two-mm thick A1050 pure aluminum plates were successfully joined by conventional and rapid cooling friction stir welding(FSW), respectively. The microstructure and mechanical properties of the welded joints were investigated by electron backscatter diffraction characterization, Vickers hardness measurements, and tensile testing. The results showed that liquid CO_(2) coolant significantly reduced the peak temperature and increased the cooling rate, so the rapidly cooled FSW joint exhibited fine grains with a large number of dislocations. The grain refinement mechanism of the FSW A1050 pure aluminum joint was primarily attributed to the combined effects of continuous dynamic recrystallization, grain subdivision, and geometric dynamic recrystallization. Compared with conventional FSW, the yield strength, ultimate tensile strength, and fracture elongation of rapidly cooled FSW joint were significantly enhanced, and the welding efficiency was increased from 80% to 93%. The enhanced mechanical properties and improved synergy of strength and ductility were obtained due to the increased dislocation density and remarkable grain refinement. The wear of the tool can produce several WC particles retained in the joint, and the contribution of second phase strengthening to the enhanced strength should not be ignored.

关键词： aluminum alloy friction stir welding recrystallization microstructure mechanical properties

Microstructure and Corrosion Resistance of Arc Additive Manufactured 316L Stainless Steel

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Journal of Wuhan University of Technology(Materials Science) 2020年第5期35卷 930-936页

作者： YANG Ke WANG Qiuyu QU Yang JIANG Yongfeng bao yefeng College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213022China Nantong Ocean and Coastal Engineering Research Institute Hohai UniversityNantong 226019China

The gas tungsten arc welding based additive manufacturing (GTAW-AM) was carried out by printing 316L austenitic stainless steel on carbon steel substrate with different arc currents (140,160,180 A).Microstructure and corrosion resistance of additive manufactured components were *** results show that the microstructure of the GTAW-AM austenitic stainless steel is obviously changed by the arc *** arc current increasing from 140 to 180 A,the austenite grains become coarse due to the effect of welding heat ***,the quantity of ferrites in the austenite matrix is decreased and the morphology transforms from lath to ***,σ phases are finally formed under the arc currents of 180 A owing to high welding heat ***,as the microstructure transform into coarse-grained austenites,low-quantity ferrites and new-generated σ phases,the GTAW-AM austenitic stainless steel presents a significantly decrease in corrosion *** the reduction of corrosion resistance is mainly due to the formation of σ phase as a result from consuming the large amounts of Cr element from the matrix.

关键词： austenitic stainless steel additive manufacturing microstructure corrosion resistance

The Effects of WC on the Microstructures and Wear Resistance of FeCoCrNiB_(0.2) High Entropy Alloy

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Journal of Wuhan University of Technology(Materials Science) 2023年第2期38卷 416-422页

作者： bao yefeng GUO Linpo ZHONG Chonghui XIE Bingqi WANG Zirui SONG Qining JIANG Yongfeng College of Mechanical and Electrical Engineering Hohai UniversityChangzhou213022China Zhejiang Sanhua Automotive Components Co. LtdHangzhou310018China

To improve the wear resistance of the FeCoCrNiB_(0.2)high entropy alloy(HEA),the FeCoCrNiB_(0.2)(WC_(0))and FeCoCrNiB_(0.2)+20wt%WC(WC_(20))HEA coatings were prepared on Q235 steel by laser cladding(LC).The microstructure,hardness,and tribometer of the HEA coatings were investigated using scanning electron microscopy with spectroscopy(SEM/EDS),X-ray diffraction(XRD),vickers microhardness tester,and pin-on-disc tribometer,*** experimental results show that the WC0HEA coating comprises a simple BCC phase mixed with an M_(2)B *** 20wt%WC,the WC_(20)HEA coating is composed of a simple BCC phase mixed with the Cr_(23)C_(6)carbide *** microstructure of the WC_(20)HEA coating is simple,which consists of equiaxed grain and *** microhardness also increases from 625.5HV to 806.0HV,and the wear mass loss correspondingly decreases from 30.9 to 14.9 mg.W and C atoms formed by WC dissolution are mainly dissolved in the BCC phase,which leads to the solution strengthening ***,Cr_(23)C_(6)carbides inhibit the growth of the grains,play the role of fine-grain strengthening,and further improve the hardness and wear resistance of the HEA coating.

关键词： high-entropy alloys laser processing and cladding microstructures hardness wear-resistance

High-temperature Tensile Behavior of Laser Welded Ti-22Al-25Nb Joints at Different Temperatures

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Journal of Wuhan University of Technology(Materials Science) 2020年第6期35卷 1116-1121页

作者： ZHANG Kezhao LEI Zhenglong CHEN Yanbin YAN Chunyan FU Qiang bao yefeng College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213022China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

The high-temperature tensile behavior of laser welded Ti-22Al-25Nb (at%) joints was investigated at 500,650,800,and 1 000 ℃.The temperatures for tensile tests were selected according to the phase transformation sequence of Ti2AlNb-based *** temperatures lower than the B2+O phase field (500 ℃) and higher than the B2+O phase field (1 000 ℃),the joints fracture in the base metal in ductile fracture *** contrast,the joints exhibit obvious high-temperature brittleness in the B2+O phase field (650 °C and 800 ℃).Heat treatments were conducted with respect to the thermal history of tensile *** microcracks along the grain boundary of B2 phase are found in the fusion zone after the heat treatments at 650 ℃ and 800 ℃.The high-temperature brittleness at 650 ℃ and 800 ℃ is attributed to the B2→O transformation along the grain *** stress concentration caused by the volume change of B2→O transformation also contributes to the high-temperature brittleness of laser welded Ti-22Al-25Nb joints.

关键词： high-temperature tensile behavior laser welding Ti2AlNb-based alloys phase transformation

Microstructure and Wear Resistance of Fe_(4)CoCrNiB_(0.2)Mo_(x)(x=0,0.5,1) High Entropy Alloys

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Journal of Wuhan University of Technology(Materials Science) 2022年第2期37卷 261-269页

作者： bao yefeng GUO Linpo ZHONG Chonghui SONG Qining YANG Ke JIANG Yongfeng WANG Zirui College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213002China

To improve the wear resistance of Fe_(4)CoCrNiB_(0.2) high-entropy alloy(HEA),the Fe_(4)CoCrNiB_(0.2)Mo_(x)(where,x in Fe_(4)CoCrNiB_(0.2)Mo_(x) is a molar content,and the value is 0,0.5,1,respectively)HEAs were prepared on the Q235 substrate by laser *** structure,hardness,and wear resistance of Fe_(4)CoCrNiB_(0.2)Mo_(x) HEAs were investigated using scanning electron microscopy with spectroscopy(SEM/EDS),X-ray diffraction(XRD),Vickers microhardness tester,and pin-on-disc *** influences of Mo content on the phase structures and mechanical properties of Fe_(4)CoCrNiB_(0.2)Mo_(x) HEAs are *** experimental results show that the Fe_(4)CoCrNiB_(0.2)Mo_(x) HEA cladding layers are composed of a simple BCC phase mixed with M_(2)B phase,BCC phase,and BCC+FCC dual-phase,*** wear resistance and hardness of the Fe_(4)CoCrNiB_(0.2)Mo HEA sample are 2 and 1.35 times those of the Fe_(4)CoCrNiB_(0.2) HEA sample,*** microhardness and wear resistance of the Fe_(4)CoCrNiB_(0.2)Mo_(x) HEAs increase with the increase of Mo *** is found that the Fe_(4)CoCrNiB_(0.2)Mo_(x) HEA cladding layers are mainly strengthened by the solid solution strengthening and fine-grained strengthening.

关键词： SEM XRD high-entropy alloys laser cladding

Study on prediction model of cavitation erosion incubation period of duplex stainless steel surfacing layer in a benign medium

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Acta Mechanica Sinica 2022年第8期38卷 112-121页

作者： yefeng bao Chong Cao Bingqi Xie Qining Song Yongfeng Jiang Nan Xu College of Mechanical and Electrical Engineering Hohai UniversityChangzhou213022China Fujian Fuqing Nuclear power Co. LtdFuqing350300China

In order to estimate the cavitation incubation period of duplex stainless steel(DSS)under ultrasonic cavitation erosion(CE),this paper analyzed the loading process of material during ultrasonic *** strain theory,cumulative damage theory,and Bernoulli probability model were used to derive the minimum number of cavitation impacts required for the initiation of fatigue cracks,and the predictive equation of the material cavitation incubation period was *** was obtained by tungsten inert gas welding(TIG)powder surfacing *** test and ultrasonic CE test were performed,and the tensile test data were used to calculate the cavitation incubation period by using the predictive *** to the possible presence of precipitates and micro-cracks in the sample,there was an error between the calculated and the test *** results showed that the max error between the calculated results and the test results was 8.1%,and the errors of the remaining two groups were within 3.5%.

关键词： Duplex stainless steel Ultrasonic cavitation erosion Incubation period Calculation Tensile properties

微观组织对镁合金FSW焊缝应变硬化行为的影响

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焊接学报 2020年第11期41卷 7-12,I0001页

作者：许楠冯若男宋亓宁包晔峰河海大学常州213022

采用传统搅拌摩擦焊和冷源辅助搅拌摩擦焊对3 mm厚的AZ31B镁合金进行焊接.利用电子背散射衍射、透射电子显微镜和静拉伸试验研究焊缝区的微观组织对力学性能的影响.结果表明,液态二氧化碳不仅降低焊接峰值温度,还提高焊后冷却速度.焊缝... 详细信息

采用传统搅拌摩擦焊和冷源辅助搅拌摩擦焊对3 mm厚的AZ31B镁合金进行焊接.利用电子背散射衍射、透射电子显微镜和静拉伸试验研究焊缝区的微观组织对力学性能的影响.结果表明,液态二氧化碳不仅降低焊接峰值温度,还提高焊后冷却速度.焊缝峰值温度的降低为激活{10-12}孪生行为创造了有利条件.{10-12}孪晶可降低基面织构的强度,也可进一步分割晶粒,起到细化晶粒的作用.焊后冷却速度的提高使焊接过程中产生的大量位错保留在晶粒内部.因此冷源辅助搅拌摩擦焊缝表现为具有大量{10-12}孪晶和位错的细晶结构.在拉伸过程中,细晶强化和位错强化为主要强化机制.孪晶界面可有效吸收和分解变形时产生的位错,从而协调应变和减小应力集中,使焊缝具有合理的应变硬化行为和强塑性匹配.

关键词：镁合金搅拌摩擦焊微观组织应变硬化行为力学性能

T2纯铜大载荷超低速搅拌摩擦焊接头强韧化机理

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焊接学报 2018年第12期39卷 63-66,131,132页

作者：许楠梁庆津周璐包晔峰河海大学机电工程学院常州213022

采用大载荷超低速搅拌摩擦焊工艺对2 mm厚的T2纯铜进行焊接,利用光学显微镜、扫描/透射电子显微镜、电子背散射衍射、硬度测试以及静拉伸试验对焊接接头的微观组织和力学性能进行研究.结果表明,焊接热循环得到显著改善,有效抑制了由焊... 详细信息

采用大载荷超低速搅拌摩擦焊工艺对2 mm厚的T2纯铜进行焊接,利用光学显微镜、扫描/透射电子显微镜、电子背散射衍射、硬度测试以及静拉伸试验对焊接接头的微观组织和力学性能进行研究.结果表明,焊接热循环得到显著改善,有效抑制了由焊后余热带来的退火软化作用,彻底消除热影响区.搅拌区由含有大量孪晶组织的超细晶构成,搅拌区抗拉强度和断后伸长率分别较母材提高了94%和69%.文中提供了一种简单有效的方法,可同时提高纯铜搅拌摩擦焊搅拌区的强度和韧性.

关键词：纯铜搅拌摩擦焊再结晶微观组织力学性能

敏化处理对2209双相不锈钢堆焊层点蚀行为的影响

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焊接学报 2020年第2期41卷 33-38,I0002,I0003页

作者：柳昱包晔峰宋亓宁蒋永锋河海大学常州213000 河海大学疏浚技术教育部工程研究中心常州213000

在850℃下,对2209双相不锈钢堆焊试样进行不同时间(15 min,30 min,1 h,2 h)的敏化处理.通过浸泡试验和交流阻抗试验研究了敏化时间对2209双相不锈钢堆焊层耐点蚀性能的影响.结果表明,对于不同时间敏化处理的试样,点蚀均起源于铁素体相;... 详细信息

在850℃下,对2209双相不锈钢堆焊试样进行不同时间(15 min,30 min,1 h,2 h)的敏化处理.通过浸泡试验和交流阻抗试验研究了敏化时间对2209双相不锈钢堆焊层耐点蚀性能的影响.结果表明,对于不同时间敏化处理的试样,点蚀均起源于铁素体相;点蚀速率与敏化时间相关,敏化处理时间小于30 min时,堆焊层的点蚀失重不明显,当敏化时间大于30 min时,点蚀失重量明显上升.阻抗谱结果显示容抗弧曲率半径随着敏化时间的增加呈不断减小的趋势,说明钝化膜的稳定性下降,耐点蚀性能下降,与浸泡试验的结果吻合.

关键词： 2209双相锈钢堆焊层敏化处理点蚀

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