Traditional high strength engineering alloys suffer from serious surface brittleness and inferior wear performance when servicing under sliding contact at cryogenic temperature.Here,we report that the recently emergin...Traditional high strength engineering alloys suffer from serious surface brittleness and inferior wear performance when servicing under sliding contact at cryogenic temperature.Here,we report that the recently emerging CoCrNi multi-principal element alloy defies this trend and presents dramatically enhanced wear resistance when temperature decreases from 273 to 153 K,surpassing those of cryogenic austenitic steels.The temperature-dependent structure characteristics and deformation mechanisms influencing the cryogenic wear resistance of CoCrNi are clarified through microscopic observation and atomistic simulation.It is found that sliding-induced subsurface structures show distinct scenarios at different deformation temperatures.At cryogenic condition,significant grain refinement and a deep plastic zone give rise to an extended microstructural gradient below the surface,which can accommodate massive sliding deformation,in direct contrast to the strain localization and delamination at 273 K.Meanwhile,the temperature-dependent cryogenic deformation mechanisms(stacking fault networks and phase transformation)also provide additional strengthening and toughening of the subsurface material.These features make the CoCrNi alloy particularly wear resistant at cryogenic conditions and an excellent candidate for safety–critical applications.展开更多
The deformation mechanism of CoCrNi alloy with high density of annealing twins was studied by in situ transmission electron microscopy. Dislocation transmission and reflection at the twin boundary were observed during...The deformation mechanism of CoCrNi alloy with high density of annealing twins was studied by in situ transmission electron microscopy. Dislocation transmission and reflection at the twin boundary were observed during in situ loading. We characterized these reaction processes by combining TEM, dislocation theory and crystallography of twin. Twin boundary not only strengthens the material by impeding the motion of dislocation, but also acts as dislocation source to produce large of slip bands. These processes generate large of slip bands to accommodate the plastic deformation or strengthening material.展开更多
采用涂敷和预制2种方式加入CoCrNi中熵粉末,研究该合金化粉末对铝/钢TIG熔钎焊接头形貌和组织性能的影响。试验结果表明:钢侧坡口涂敷中熵合金粉时,钎接面有椭球状未熔CoCrNi颗粒层存在,颗粒周围缝隙由灰色的Al基体和Al 0.7 Si 3Fe 0.3...采用涂敷和预制2种方式加入CoCrNi中熵粉末,研究该合金化粉末对铝/钢TIG熔钎焊接头形貌和组织性能的影响。试验结果表明:钢侧坡口涂敷中熵合金粉时,钎接面有椭球状未熔CoCrNi颗粒层存在,颗粒周围缝隙由灰色的Al基体和Al 0.7 Si 3Fe 0.3填充,界面两侧Al、Fe无明显元素扩散,残余CoCrNi颗粒一定程度上起到了增强相作用,但是其大小和分布的不均匀性影响了液态AlSi_(5)焊丝的流动,背面焊缝包覆性差,形成了较高余高和底部未熔合缺陷。预制方式下CoCrNi粉熔化与钢界面结合良好,熔敷金属在铝和钢表面有较好铺展,接头成形好,界面两侧各元素发生相互扩散,界面生成了Al_(0.7)Si_(3)Fe_(0.3)、Co_(3)Fe_(7)、Fe(Cr,Ni)和Al_(0.9)Ni_(1.1),金属间化合物(IMC)层平均厚3.15μm。CoCrNi中熵粉末有效阻隔了Al-Fe金属间化合物生成,2种方式下接头强度均大于未添加中熵合金粉的接头,其中预制中熵合金粉的强度较高(86 MPa)。涂敷中熵合金粉的接头维氏硬度最高达到467HV,位于钎接界面近焊缝侧,预制中熵合金粉的钢侧出现软化区,接头维氏硬度最高为248HV,位于近钎接界面钢侧。展开更多
基金supported by the National Natural Science Foundation of China(52175188 and 51975474)National Key R&D Program of China(2022YFB3705300)+3 种基金Key Research and Development Program of Shaanxi Province(2023-YBGY-434)the Fundamental Research Funds for the Central Universities(3102019JC001)Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(LKLAMTF202301)C.G.acknowledges funding by the German Research Foundation(DFG)under Project G.R.4174/5 and by the European Research Council(ERC)under Grant No.771237.
文摘Traditional high strength engineering alloys suffer from serious surface brittleness and inferior wear performance when servicing under sliding contact at cryogenic temperature.Here,we report that the recently emerging CoCrNi multi-principal element alloy defies this trend and presents dramatically enhanced wear resistance when temperature decreases from 273 to 153 K,surpassing those of cryogenic austenitic steels.The temperature-dependent structure characteristics and deformation mechanisms influencing the cryogenic wear resistance of CoCrNi are clarified through microscopic observation and atomistic simulation.It is found that sliding-induced subsurface structures show distinct scenarios at different deformation temperatures.At cryogenic condition,significant grain refinement and a deep plastic zone give rise to an extended microstructural gradient below the surface,which can accommodate massive sliding deformation,in direct contrast to the strain localization and delamination at 273 K.Meanwhile,the temperature-dependent cryogenic deformation mechanisms(stacking fault networks and phase transformation)also provide additional strengthening and toughening of the subsurface material.These features make the CoCrNi alloy particularly wear resistant at cryogenic conditions and an excellent candidate for safety–critical applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.51571046 and 51421001)the Fundamental Research Funds for the Central Universities(Grant No.2018CDJDCL0019)the“111”Project(Grant No.B16007)by the Ministry of Education and the State Administration of Foreign Experts Affairs of China。
文摘The deformation mechanism of CoCrNi alloy with high density of annealing twins was studied by in situ transmission electron microscopy. Dislocation transmission and reflection at the twin boundary were observed during in situ loading. We characterized these reaction processes by combining TEM, dislocation theory and crystallography of twin. Twin boundary not only strengthens the material by impeding the motion of dislocation, but also acts as dislocation source to produce large of slip bands. These processes generate large of slip bands to accommodate the plastic deformation or strengthening material.
