应变速率对Fe-20Mn-3Al-3Si钢的力学性能及其微观组织的影响

分别采用分离式Hopkinson压杆和MTS Landmark电液伺服疲劳试验机对冷轧退火态Fe-20Mn-3Al-3Si相变诱导塑性(transformation induced plasticity,TRIP)钢进行900 s^(-1)~3500s^(-1)范围内的动态冲击实验和应变速率为3×10^(-3)s^(-1)准静态压缩实验.采用X射线衍射技术(X-ray diffraction,XRD)、电子背散射衍射技术(electron backscatter diffraction,EBSD)和透射电镜(transmission electron microscope,TEM)等对变形试样的微观组织结构进行表征.结果表明,该TRIP钢表现出正应变速率敏感性,且动态冲击变形的屈服强度明显高于准静态变形的屈服强度.无论是在动态冲击样品还是准静态压缩样品中,都可以观察到大量的ε-马氏体和α'-马氏体,且动态冲击样品中ε-马氏体和α'-马氏体的体积分数明显低于准静态变形样品中ε-马氏体和α'-马氏体的体积分数.在动态冲击样品中,除了能观察到大量的ε-马氏体和α'-马氏体以外,也可以观察到大量的{1011}ε_(T)孪晶和{1012}ε_(T)孪晶,并且,{1011}ε_(T)孪晶和α'-马氏体之间的取向关系为(110)α'//(0002)ε_(T),<111>α'//<2110>ε_(T).

Spray deposition of FeCrNiMn and high carbon steel coatings by thermite reaction

A novel surface cladding technique was developed to prepare the FeCrNiMn alloy and high carbon steel cladding layers,and the microhardness,bonding strength,abrasion wear and corrosion resistance were investigated.The microstructures of the cladding layers were analyzed by using X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).The results show that the bonding strength between the substrate and the two cladding layers were(432.6±21)and(438.3±12)MPa,respectively.Vickers hardness values of the two cladding layers were HV418.5and HV329.6,respectively.The corrosion current densities of the two coatings were2.926×10–6and6.858×10–6A/cm2after electrochemical corrosion test in3.5%NaCl solution,and the wear rate were1.78×10–7and1.46×10–6mm3/mN after sliding wear test,respectively.This indicates that a well metallurgical bonding between the coating and the substrate was achieved,the abrasion wear and corrosion resistance of both coatings had been greatly improved compared with the substrate.The novel cladding technology is promising for preparing wear-and-corrosion resistant coatings.

冷轧变形量对Mn12Ni2MoTi(Al)钢层状双相结构的影响

采用扫描电镜(SEM)、X射线衍射(XRD)、电子背散射衍射(EBSD)、电子探针(EPMA)和室温单轴拉伸实验研究了冷轧变形量及后续退火对Mn12Ni2MoTi(Al)钢的层状结构微观组织及其拉伸性能的影响。结果表明:冷轧变形量越大,退火后越容易形成奥氏体(γ)、马氏体或铁素体(α)交替排列的层状双相结构;745℃1 h+480℃12 h二次退火有利于材料中奥氏体含量的提高,并有利于γ/α’层状结构的形成;层状双相结构组织往往存在强烈的织构和Mn元素的偏聚。当双相钢具有层状结构时,其强度和塑性同时提高。