【作者】 罗明亮；

【导师】 李宁； 杨德勇；

【作者基本信息】 四川大学 ， 机械工程（专业学位）， 2021， 硕士

【摘要】 Fe-11Cr-2.5Mo-1Ni双相阻尼合金具有优良的力学性能,同时兼备良好的阻尼性能,相较于传统的单相Fe-Cr阻尼合金,解决了后者在较大应力下阻尼性能衰减较快的问题,拥有广阔的工程应用前景。但作为结构功能一体化的材料,在实际工程应用时肯定会遇到连接问题,如输气管道、桥梁支撑架的连接,焊缝的性能会直接对连接的可靠性及减振降噪的效果产生影响。本文首先用TIG焊对阻尼钢板进行本体焊接、316L焊接;然后用WDW-RD100疲劳试验机、动态机械分析仪(DMA)、万能拉伸试验机(RGM-4300)、盐雾试验机、夏比冲击试验机(JB-300B)、HV-50A硬度测试仪等设备研究了焊后阻尼钢板的疲劳性能、阻尼性能和力学性能,用金相显微镜(Olympus GX51)和扫描电子显微镜(SEM)观察了焊缝的微观组织形貌,并对其成分做了(EDS)能谱分析,主要得出以下结论:(1)Fe-11Cr-2.5Mo-1Ni阻尼钢板焊缝经不同温度热处理后,微观组织呈现出明显差异,800℃保温1小时随炉冷却热处理的焊缝组织为单相铁素体,900℃热处理的阻尼钢板焊缝组织为马氏体和铁素体,马氏体主要分布在焊缝熔合线上,以团状和长条状的形态存在,1000℃热处理后焊缝的马氏体含量最多,在晶界上和晶粒内部都有广泛分布。(2)随着焊后热处理温度(800℃、900℃、1000℃)升高,焊接拉伸试样的屈服强度Rp0.2和抗拉强度Rm随之升高,断后延伸率变化规律与之相反,热处理温度越高,延伸率越低。经800℃-保温1小时-随炉冷却热处理的焊接拉伸试样屈服强度Rp0.2和抗拉强度Rm最低,只有264MPa和395MPa,但延伸率最高,有39.6%,1000℃热处理后的焊接拉伸试样屈服强度(Rp0.2)和抗拉强度(Rm)最高,Rp0.2为282MPa,Rm为413MPa,但其延伸率最低,为33.3%;此外,在进行拉伸实验时试样的断裂位置都位于母材处,说明焊缝的强度高于钢板母材。(3)随着热处理温度升高,焊缝的维氏硬度随之升高,1000℃保温1小时随炉冷却热处理的焊缝含有较多的马氏体,所以硬度值最高,有163HV,800℃热处理的焊缝因为母材和焊缝的组织都为铁素体,所以两个区域的硬度相差不大,都在143HV左右。900℃保温1小时随炉冷却热处理的焊缝试样冲击性能最好,有236J,1000℃热处理后的焊接试样在焊缝处有较多马氏体,所以冲击性能低一些,只有190J。(4)随着热处理温度升高(800℃~1000℃),钢板焊缝的内耗值呈现出先增加再减少的趋势。其中900℃-保温1小时-随炉冷却热处理的钢板焊缝阻尼性能最好,在预应力为24MPa,应变振幅为9.6×10-5时,内耗Q-1能达到0.056,并且随着预应力增加,合金内耗值的衰减幅度不大,这主要得益于引入马氏体相后增加的平行位错在预应力下使位错阻尼被激活,从一定程度上弥补磁机械滞后阻尼因外加应力增大而下降的部分;此外,不同温度热处理后的焊接阻尼钢板,横焊缝试样和纵焊缝试样的阻尼性能相差不大,说明焊缝的方向性并不会对焊后阻尼钢板的内耗值产生太大影响。(5)对900℃-保温1小时-随炉冷却热处理的焊接阻尼钢板进行疲劳试验,在应力上峰为0.6RP0.2(3.86KN),应力比R为0.1,下峰为0.386KN,频率为10HZ的条件下,试样疲劳200万次未断裂,当应力上峰提升至0.8Rp0.2(5.15KN),下峰为0.515KN时,合金疲劳至197万次时在焊缝处断裂,通过扫描电镜在其断口上看到了明显疲劳条带和疲劳辉纹。更多还原

【Abstract】 Fe-11Cr-2.5Mo-1Ni dual phase damping alloy has excellent mechanical properties and good damping properties.Compared with the traditional single-phase Fe-Cr damping alloy,It solves the problem that the damping performance of the latter decays rapidly under large stress,and has a broad engineering application prospect.However,as a material with integrated structure and function,it will definitely encounter connection problems in practical engineering application,such as the connection of gas transmission pipeline and bridge support frame.The performance of welding seam will directly affect the reliability of connection and the effect of vibration and noise reduction.In this paper,the damping steel plate is welded by TIG welding and 316 L welding;Then the fatigue properties,damping properties and mechanical properties of the damping steel plate after welding were studied by WDW-RD100 fatigue testing machine、Dynamic mechanical analyzer(DMA),universal tensile testing machine(RGM-4300),salt spray testing machine,Charpy impact testing machine(JB-300b),HV-50 A hardness tester.The microstructure of the weld was observed by optical microscope(Olympus GX51)and scanning electron microscope(SEM),and its composition was analyzed by energy dispersive spectroscopy(EDS),The main conclusions are as follows:(1)The microstructure of Fe-11Cr-2.5Mo-1Ni damping steel plate weld after heat treatment at different temperatures shows obvious differences.The microstructure of the weld after heat treatment at 800 ℃ for 1 hour is single-phase ferrite.The microstructure of the weld after heat treatment at 900 ℃ is martensite and ferrite.Martensite is mainly distributed in the weld fusion line and exists in the form of clusters and strips,After heat treatment at 1000 ℃,the martensite content in the weld is the most,which is widely distributed on the grain boundary and inside the grain.(2)With the increase of post weld heat treatment temperature(800 ℃,900 ℃,1000 ℃),the yield strength Rp0.2 and tensile strength rm of welded tensile specimens increase.The change rule of elongation after fracture is opposite to that.The higher the heat treatment temperature is,the lower the elongation is.The yield strength(Rp0.2)and tensile strength(Rm)of welded tensile specimens after 800 ℃-holding for 1 hour-cooling in furnace are the lowest,only 264 MPa and 395 MPa,but the elongation is the highest,39.6%.The yield strength(Rp0.2)and tensile strength(Rm)of welded tensile specimens after 1000 ℃ heat treatment are the highest,Rp0.2 is282 MPa,Rm is 413 MPa,but the elongation is the lowest,33.3%;In addition,in the tensile test,the fracture position of the sample is located in the base metal,which indicates that the strength of the weld is higher than that of the steel plate.(3)With the increase of heat treatment temperature,the Vickers hardness of the weld increases.The weld with 1000 ℃ heat treatment for 1 hour contains more martensite,so the hardness value is the highest,with 163 HV.Because the microstructure of base metal and weld with 800 ℃ heat treatment is ferrite,the hardness of the two areas is almost the same,about 143 HV.The weld samples with900 ℃ holding for 1 hour and furnace cooling heat treatment have the best impact property,236 J.The weld samples with 1000 ℃ heat treatment have more martensite,so the impact property is lower,only 190 J.(4)With the increase of heat treatment temperature(800 ℃ ~ 1000℃),the internal friction value of steel plate weld first increases and then decreases.The results show that the damping property of the steel plate weld is the best when the prestress is 24 MPa and the strain amplitude is 9.6 × 10-5 The results show that the internal friction Q-1can reach 0.056,and the attenuation of internal friction is small with the increase of prestress,which is mainly due to the activation of dislocation damping due to the increase of parallel dislocations after the introduction of martensite phase,which makes up for the decrease of magnetomechanical hysteresis damping due to the increase of applied stress to a certain extent;In addition,there is no significant difference in the damping properties between the transverse weld and the longitudinal weld after heat treatment at different temperatures,which indicates that the directivity of the weld does not have much influence on the internal friction value of the damping steel plate after welding.(5)The fatigue test of welded damping steel plate was carried out at 900 ℃-holding for 1 hour-furnace cooling heat treatment.Under the condition of stress peak of 0.6Rp0.2(3.86KN),stress ratio R of 0.1,lower peak of 0.386 KN and frequency of 10 Hz,the sample did not fracture for 2 million times of fatigue.When the stress peak of 0.8Rp0.2(5.15KN)and lower peak of 0.515 KN,the alloy fractured at the weld for 1.97 million times of fatigue,Obvious fatigue bands and striations were observed on the fracture surface by SEM.更多还原