A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It...A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It was shown that a combination of high scan speed and high laser energy density made WC on the edge of WC-12 Co composite powders partially melt in liquid Co and 304 stainless steel matrix, and then new carbides consisting of lamellar WC and herringbone M3 W3 C(M=Fe,Co) were formed. Meanwhile, WC-12 Co composite coatings with no porosity, cracks and drawbacks like decarburization were obtained, showing high densification and good metallurgical bonding with the substrate. Furthermore, a considerably high microhardness of HV0.3 1500-1600, low coefficient of friction of 0.55 and wear rate of(2.15±0.31)×10-7 mm3/(N·m) were achieved owing to the synergistic effect of excellent metallurgical bonding and fine microstructures of composite coating under laser power of 1500 W.展开更多
The evolution of microstructure and microhardness was studied in a commercial tungsten-25%rhenium(mass fraction)(W-25Re)alloy processed by the high pressure torsion(HPT)procedure under a pressure of7.7GPa up to10revol...The evolution of microstructure and microhardness was studied in a commercial tungsten-25%rhenium(mass fraction)(W-25Re)alloy processed by the high pressure torsion(HPT)procedure under a pressure of7.7GPa up to10revolutions at different temperatures.The results show that the samples processed by10revolutions at room temperature could have the smallest grain size at around0.209μm.High saturation hardness(HV^1200)could be achieved after the rapid strengthening stage for samples processed by10revolutions both at room temperature and at573K.Microstructural observation and analysis from Hall-Patch relationship could reveal that grain refinement and grain boundaries strengthening are the main factors of hardening mechanism in W-25Re alloy.It is also demonstrated that sintered W-25Re sample may have brittle phase separation phenomenon after HPT processing.展开更多
A solution-treated AZ91 bulk material was deep-surface-rolled at room temperature to investigate the effect of deep surface rolling on the microstructure and mechanical properties of the alloy. Microhardness and micro...A solution-treated AZ91 bulk material was deep-surface-rolled at room temperature to investigate the effect of deep surface rolling on the microstructure and mechanical properties of the alloy. Microhardness and microstructure along the depth of the treated surface layer were characterized. The results show that the affected layer was up to 2.0 mm thick and consisted of three sublayers: a severe deformation layer with thickness of about 400 μm from the topmost surface, a medium deformation layer with thickness of around 600 μm and a small deformation layer up to 1000 μm thick. In addition to grain refinement in the deformation layer, strain-induced precipitation of β phase (Mg17Al12) was observed, particularly in the severe and medium deformation layers. It is believed that the cooperative effects of grain refinement, strain hardening and precipitation strengthening led to the significant increase in hardness of the AZ91 alloy after the deep surface rolling.展开更多
基金Project(20171ACE50018)supported by the Key Research and Development Program of Jiangxi Province,ChinaProject(2017-YZD2-16)supported by the Key Research Project of Jiangxi Academy of Sciences,China。
文摘A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It was shown that a combination of high scan speed and high laser energy density made WC on the edge of WC-12 Co composite powders partially melt in liquid Co and 304 stainless steel matrix, and then new carbides consisting of lamellar WC and herringbone M3 W3 C(M=Fe,Co) were formed. Meanwhile, WC-12 Co composite coatings with no porosity, cracks and drawbacks like decarburization were obtained, showing high densification and good metallurgical bonding with the substrate. Furthermore, a considerably high microhardness of HV0.3 1500-1600, low coefficient of friction of 0.55 and wear rate of(2.15±0.31)×10-7 mm3/(N·m) were achieved owing to the synergistic effect of excellent metallurgical bonding and fine microstructures of composite coating under laser power of 1500 W.
基金Project(11402264)supported by the National Natural Science Foundation of ChinaProject(BK20160182)supported by the Natural Science Foundation of Jiangsu Province,ChinaProjects(JUSRP116027,JUSRP51732B)supported by the Fundamental Research Funds from Jiangnan University,China
文摘The evolution of microstructure and microhardness was studied in a commercial tungsten-25%rhenium(mass fraction)(W-25Re)alloy processed by the high pressure torsion(HPT)procedure under a pressure of7.7GPa up to10revolutions at different temperatures.The results show that the samples processed by10revolutions at room temperature could have the smallest grain size at around0.209μm.High saturation hardness(HV^1200)could be achieved after the rapid strengthening stage for samples processed by10revolutions both at room temperature and at573K.Microstructural observation and analysis from Hall-Patch relationship could reveal that grain refinement and grain boundaries strengthening are the main factors of hardening mechanism in W-25Re alloy.It is also demonstrated that sintered W-25Re sample may have brittle phase separation phenomenon after HPT processing.
基金Project(2016ZE53046)supported by the Aviation Science Foundation of ChinaProject(201606295009)supported by the China Scholarship CouncilProject supported by Top International University Visiting Program for Outstanding Young Scholars of Northwestern Polytechnical University,China
文摘A solution-treated AZ91 bulk material was deep-surface-rolled at room temperature to investigate the effect of deep surface rolling on the microstructure and mechanical properties of the alloy. Microhardness and microstructure along the depth of the treated surface layer were characterized. The results show that the affected layer was up to 2.0 mm thick and consisted of three sublayers: a severe deformation layer with thickness of about 400 μm from the topmost surface, a medium deformation layer with thickness of around 600 μm and a small deformation layer up to 1000 μm thick. In addition to grain refinement in the deformation layer, strain-induced precipitation of β phase (Mg17Al12) was observed, particularly in the severe and medium deformation layers. It is believed that the cooperative effects of grain refinement, strain hardening and precipitation strengthening led to the significant increase in hardness of the AZ91 alloy after the deep surface rolling.
