The influence of solid-solution temperature on the dissolution of carbide precipitates, the average grain size and the microhardness of the austenite matrix in an Fe-Ni based high strength low thermal expansion （HSLT...The influence of solid-solution temperature on the dissolution of carbide precipitates, the average grain size and the microhardness of the austenite matrix in an Fe-Ni based high strength low thermal expansion （HSLTE） alloy was investigated to obtain the proper temperature range of the solid-solution process. The XRD analysis, microstructure observations, and the theoretical calculations showed that the Mo-rich M2C-type precipitates in the Fe-Ni based HSLTE alloy dissolve completely at about 1100℃. The average grain size of the studied alloys increases from 14 to 46 μm in the temperature range of 1050 to 1200℃. The microhardness of the matrix decreases gust for the sake of solid-solution treatment, but then increases later with increasing solution temperature because of the solution strengthening effect.展开更多
A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, che...A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.展开更多
Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . ...Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .展开更多
It is important to inhibit the precipitation of η phases in precipitation strengthened Fe-Ni based alloys,as they will deteriorate not only the mechanical property but also the hydrogen resistance.The present investi...It is important to inhibit the precipitation of η phases in precipitation strengthened Fe-Ni based alloys,as they will deteriorate not only the mechanical property but also the hydrogen resistance.The present investigation shows that grain boundary engineering(GBE) can retard the formation and growth of ηphase in J75 alloy.After GBE treatment with 5% cold rolling followed by annealing at 1000℃ for 1 h,the fraction of special boundaries(SBs) increases from 38.4% in conventional alloy to 77.2% and the fraction of special triple junctions increases from 10% to 74%.During 800℃ aging treatment,quite amount of cellular η phases adjacent to random grain boundary(RGB) will be found in conventional alloy,and only a few small η phases have been observed in GBE treatment alloy subjected to the same aging treatment for long time.The reason for GBE in inhibiting precipitation of η phase can be attributed to not only introducing high fraction of SBs but also breaking the connectivity of RGB networks.As nucleation and growth of η phases on SBs are difficult due to their lower Ti concentration and diffusion rate,and the disruption of RGB networks reduces supply of Ti atoms to the η phases significantly,which impedes their growth at RGB.展开更多
Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been prop...Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.展开更多
使用镍基焊缝连接铁素体基耐热钢和奥氏体不锈钢(或镍基合金)形成的异种金属焊接接头(DMWs,Dissimilar Metal Welds)在核电、火电、石化等行业有着广泛的应用。DMWs在高温低应力服役条件下经常会出现早期失效,导致机组非正常停机,带来...使用镍基焊缝连接铁素体基耐热钢和奥氏体不锈钢(或镍基合金)形成的异种金属焊接接头(DMWs,Dissimilar Metal Welds)在核电、火电、石化等行业有着广泛的应用。DMWs在高温低应力服役条件下经常会出现早期失效,导致机组非正常停机,带来巨大的经济损失和安全隐患,故DMWs的早期失效问题一直受到工程界和学术界的重点关注。围绕DMWs的早期失效问题,回顾并总结了近几十年来该领域的相关研究成果。首先,介绍了DMWs的组织特点,重点关注了铁素体基耐热钢与焊缝界面附近区域的冶金特点,包括界面马氏体层、碳迁移、Ⅰ/Ⅱ型碳化物等;其次,简要总结了DMWs焊接残余应力的特点及其影响因素;再次,汇总了DMWs的高温蠕变数据,针对DMWs蠕变断裂位置转移的特点进行了分析,其中沿铁素体基耐热钢与焊缝界面断裂是DMWs失效的显著特征,这种失效方式与界面处应变集中、热应力、基体组织退化、碳化物粗化以及氧化等有关;最后,给出了若干种延长DMWs服役寿命的方法和建议。展开更多
基金This work was financially supported by the S&T Research Development Project of the Ministry of Science and Technology, China (No.05021050).
文摘The influence of solid-solution temperature on the dissolution of carbide precipitates, the average grain size and the microhardness of the austenite matrix in an Fe-Ni based high strength low thermal expansion （HSLTE） alloy was investigated to obtain the proper temperature range of the solid-solution process. The XRD analysis, microstructure observations, and the theoretical calculations showed that the Mo-rich M2C-type precipitates in the Fe-Ni based HSLTE alloy dissolve completely at about 1100℃. The average grain size of the studied alloys increases from 14 to 46 μm in the temperature range of 1050 to 1200℃. The microhardness of the matrix decreases gust for the sake of solid-solution treatment, but then increases later with increasing solution temperature because of the solution strengthening effect.
基金The paper is supported by country-level Spark Plan in 2003,project No.: 2003EA690034.
文摘A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.
文摘Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .
基金supported by the National Natural Science Foundation of China and China Academy of Engineering Physics[No.U1730140]National Key Research and Development Program of China[Grant No.2019YFB1505201]。
文摘It is important to inhibit the precipitation of η phases in precipitation strengthened Fe-Ni based alloys,as they will deteriorate not only the mechanical property but also the hydrogen resistance.The present investigation shows that grain boundary engineering(GBE) can retard the formation and growth of ηphase in J75 alloy.After GBE treatment with 5% cold rolling followed by annealing at 1000℃ for 1 h,the fraction of special boundaries(SBs) increases from 38.4% in conventional alloy to 77.2% and the fraction of special triple junctions increases from 10% to 74%.During 800℃ aging treatment,quite amount of cellular η phases adjacent to random grain boundary(RGB) will be found in conventional alloy,and only a few small η phases have been observed in GBE treatment alloy subjected to the same aging treatment for long time.The reason for GBE in inhibiting precipitation of η phase can be attributed to not only introducing high fraction of SBs but also breaking the connectivity of RGB networks.As nucleation and growth of η phases on SBs are difficult due to their lower Ti concentration and diffusion rate,and the disruption of RGB networks reduces supply of Ti atoms to the η phases significantly,which impedes their growth at RGB.
基金supported financially by the National Natural Science Foundation of China (Nos. 51431007, 51831006 and 51771012)
文摘Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.
文摘使用镍基焊缝连接铁素体基耐热钢和奥氏体不锈钢(或镍基合金)形成的异种金属焊接接头(DMWs,Dissimilar Metal Welds)在核电、火电、石化等行业有着广泛的应用。DMWs在高温低应力服役条件下经常会出现早期失效,导致机组非正常停机,带来巨大的经济损失和安全隐患,故DMWs的早期失效问题一直受到工程界和学术界的重点关注。围绕DMWs的早期失效问题,回顾并总结了近几十年来该领域的相关研究成果。首先,介绍了DMWs的组织特点,重点关注了铁素体基耐热钢与焊缝界面附近区域的冶金特点,包括界面马氏体层、碳迁移、Ⅰ/Ⅱ型碳化物等;其次,简要总结了DMWs焊接残余应力的特点及其影响因素;再次,汇总了DMWs的高温蠕变数据,针对DMWs蠕变断裂位置转移的特点进行了分析,其中沿铁素体基耐热钢与焊缝界面断裂是DMWs失效的显著特征,这种失效方式与界面处应变集中、热应力、基体组织退化、碳化物粗化以及氧化等有关;最后,给出了若干种延长DMWs服役寿命的方法和建议。
