Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： With the development of hydrogen economy, the demand of structural materials with high strength suitable for service in hydrogen or hydrogen-bearing environments such as storage of hydrogen gas was incremental. An optional structural materials is J75 alloy, which is mainly strengthened by an ordered fcc g' phase, Ni3(Al, Ti), coherent with the austenite matrix. Investigation on J75 alloy indicated that the commercial alloy free of B would lose about half its ductility when charged with hydrogen, accompanied by a change of fracture mode from ductile rupture to brittle-appearing intergranular fracture. Otherwise, an improvement in ductility and hydrogen resistant performance was observed in the J75 alloy with trace B, however, its role in the alloy is unclear. So, in present work, mechanism of B in the J75 hydrogen-resistant alloy was investigated by means of OM, SEM, TEM, EPMA, 3DAP, SIMS, hydrogen penetration, thermal hydrogen charging experiments and tensile tests. It was found that a lot of Ti segregated at grain boundaries (GBs) in the alloy free of B, resulted in abundant precipitation of cellular h phases. However, the cellular h phase was not observed in the alloy with B, and it could be attributed to the segregation of B atoms at GBs and inhibited the segregation of Ti. A lower hydrogen diffusion coefficient was observed in the alloy with B than that in the alloy free of B by hydrogen permeation, indicating that diffusion velocity of H atoms in the alloy had been decreased by the addition of B. Moreover, segregation of B at GBs could not only inhibit the precipitation of h phases but also decrease the number of H atoms there, which would improve the hydrogen-resistant performance of the alloy.
Subjects: Materials Science >> Materials Science (General) submitted time 2017-11-21 Cooperative journals: 《金属学报》
Abstract：采用熔化极活性气体保护焊（MAG焊）对一种Fe-Cr-Ni-Mo高强高韧合金钢板进行多道次焊接，利用SEM、EPMA、TEM以及拉伸、冲击等实验研究了焊接接头的组织和力学性能。结果表明，焊缝金属由柱状晶和等轴晶组成，其中上部焊缝以柱状晶为主，而下部焊缝的等轴晶含量增加。焊缝上部因冷速较快形成回火马氏体组织；下部因合金元素含量较高，淬硬倾向较强，形成了粒状贝氏体组织。靠近焊缝的热影响区为较粗大的马氏体组织，其硬度最大（620HV），明显高于母材（410HV）。上部焊缝金属的硬度为365HV，低于母材，而下部焊缝的硬度高于焊缝上部和母材，为450HV。因此，焊接接头上部拉伸试样在焊缝处发生断裂，断裂强度为1109 MPa，而焊缝的下部拉伸样在母材处发生断裂，断裂强度为1183 MPa。本实验用Fe-Cr-Ni-Mo合金钢的焊接接头强度较高，焊接强度系数不小于0.93，焊缝金属的冲击功为53 J。
Subjects: Materials Science >> Materials Science (General) submitted time 2017-11-21 Cooperative journals: 《金属学报》
Abstract：利用透射电子显微镜（TEM）与扫描电子显微镜（SEM）探究了回火时间（10 min、20 min、40 min、120 min）对不同V含量（0%、0.08%、0.14%，质量分数）Fe-Cr-Ni-Mo高强钢碳化物转变和力学性能的影响。结果表明：淬火态0V钢在马氏体板条间析出了少量的M7C3型碳化物，而含V钢中无碳化物析出，故淬火态0V钢的强度最高（2060 MPa）。回火处理过程中，短时间回火（20 min）时，0V钢仅在板条间析出了M3C型碳化物，随着回火时间的延长（120 min），该碳化物逐渐转变为M23C6，这两种碳化物尺寸均较粗大（150~300 nm），对合金钢强度的贡献相对较弱，导致0V钢的强度逐渐下降，由回火20 min时的1197 MPa下降到回火120 min后的1088 MPa。加入V后，合金钢经短时间回火（20 min）后不仅在晶界析出M3C，还在晶内析出了数量较多的M2C，且尺寸细小（不大于80 nm），随着时间的延长，M3C逐渐分解并形成了数量较多的M6C和更稳定的MC，对合金钢的沉淀强化效果较强，且对塑韧性的影响相对较小。因此随着回火时间的延长，含V钢的强度基本保持不变，而塑韧性呈现增加的趋势，获得了良好的强韧性配合。
Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《金属学报》
Abstract：采用扫描透射电镜（STEM）和动态机械分析仪（DMA）研究了FeCrMoCu合金（Cu添加量为1.0%和2.0%）在不同冷速条件下Cu的析出行为及其对阻尼性能和力学性能的影响。结果表明：在1.0Cu合金中Cu主要以过饱和的形式固溶在基体，当冷速较慢时会析出少量的富铜bcc-Cu相，该相尺寸较小（< 5 nm），与基体共格；Cu增加到2.0%后，随着冷速的降低，先析出数量较少、尺寸较小的富铜bcc-Cu相，随后析出相长大呈球状（10~15 nm）且数量增多，最后粗化成圆棒状（100~400 nm）但数量显著减少，后两种析出相均为非共格的ε-Cu相。含Cu第二相的析出，明显增加合金平均内应力，使合金的阻尼性能显著下降，因此有第二相析出的2.0Cu合金的阻尼性能明显低于1.0Cu合金。与此同时，合金的强度随着Cu相的析出而明显提高，其中富铜bcc-Cu相的析出强化效果较好，且对塑韧性的影响相对较小。含1.0%Cu的FeCrMoCu合金可以同时获得较好的阻尼性能和力学性能。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：在9Cr2WVTa低活化铁素体/马氏体钢中添加合金元素Al及Si，研究了Al、Si对9Cr2WVTa钢显微组织、力学性能、冲击性能以及耐液态Pb-Bi共晶合金（LBE）腐蚀性能的影响。结果表明Al、Si缩小9Cr2WVTa合金的奥氏体相区，促进δ铁素体的生成，且Al元素的影响更加明显。位于马氏体与δ铁素体界面的M23C6碳化物处易产生应力集中进而形成孔洞，严重降低9Cr2WVTa合金的室温冲击性能，断口呈现脆性断裂特征。通过Al、Si的复合添加，获得了具有较好力学性能和冲击性能的9Cr2WVTa合金，合金在550℃静态LBE中的腐蚀性能明显提高，其原因在于合金内层氧化层中形成的Al和Si的氧化物，提高了内层氧化层的致密性，降低了合金元素及氧的扩散速率，从而显著提高合金的耐铅铋腐蚀性能。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract：利用透射电子显微镜研究了一种低合金钢中马氏体的微结构. 研究发现, 淬火态的马氏体由铁素体基体和弥散于基体中的高密度纳米小颗粒组成, 这种小颗粒的晶体结构可标定为六角结构的?相. ?相与铁素体基体(α-Fe)的取向关系为:[113]α//[2113]ω，(110)α//(1101)ω 和(211)α//(0110)ω, 点阵常数aω =1.414aα, cω =0.866aα. 马氏体中的碳原子呈非均匀分布, 铁素体基体具有很低的碳含量, 合金中的碳原子主要富集在ω相中.
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