形变温度对FeMnSiCrNiC合金第二相方向性析出及记忆效应的影响

基于控制第二相方向性析出提高铁基合金形状记忆效应的构想,研究了不同形变温度对Fe13.53Mn4.86Si8.16Cr3.82Ni0.16C合金γ/ε界面(母相丫与诱发马氏体ε之间界面)的数量和结构及随后时效第二相析出的数量和方向性的影响,以及第二相析出的数量和方向性对马氏体相变和形状记忆效应的影响.扫描电镜分析显示,形变温度远高于Ms时,无γ/ε面产生,时效后第二相析出少;形变温度接近Ms时,产生大量γ/ε面,时效后析出第二相数量很多,且方向性良好;形变温度进一步接近Ms时,γ/ε界面交叉,导致时效后方向性的第二相也交叉.透射电镜分析显示,析出方向性Cr23C6第二相的合金再次进行预变形时,产生的应力诱发马氏体具有单一方向.原因在于方向性Cr23C6及其产生的应力场对马氏体相交产生约束作用,避免马氏体片之间的交叉,使其具有更好的可逆转变性.     

控制第二相方向性析出对铁基合金记忆效应的影响

研究了直接时效和形变时效对Fe-13．53Mn-4．86Si-8．16Cr-3．82Ni-0．16C合金第二相析出、马氏体相变和形状记忆效应的影响．SEM和XRD分析表明,时效后有大量Cr23C6第二相析出,但直接时效析出的Cr23Ca无方向性,而形变时效后Cr23C6呈方向性析出．相同时效时间下,形变时效析出的Cr23C6数量显著增多,且尺寸减小．两种时效均都能显著提高合金的形状记忆效应,且都存在一个最佳的时效时间．形变时效后的形状记忆效应达到82％,显著高于直接时效的记忆效应（43％）．通过控制第二相方向性析出,可制备出不需训练的高形变回复能力的铁基形状记忆合金．     

形变时效温度对Fe-Mn-Si-Cr-Ni合金形状记忆效应的影响

研究了直接时效和形变时效温度对Fe-13Mn-5Si-8Cr-4Ni-0.2C合金形状记忆效应和微观组织的影响.结果表明,直接时效后Fe-Mn-Si-Cr-Ni合金在奥氏体晶界和晶内只有少量Cr23C6第二相弥散析出,而形变后再时效有大量的Cr23C6在奥氏体晶内沿某些特定的方向析出,显著强化基体的同时提高了ε马氏体的可逆逆转变性.形变时效温度影响第二相的析出数量和方向性,从而影响合金的形状记忆效应,存在一个最佳的时效温度.当形变后在1073 K时效300 min时,不仅第二相数量多且在晶内析出的方向性好,合金的形状记忆效应达到89%.     

Phase precipitation behavior and tensile properties of as-cast Ni-based superalloy during heat treatment

The phase precipitation behavior and tensile properties of an as-cast Ni-based alloy, IN617B alloy, after solution heat treatment and long-term aging treatment were investigated. Ti(C,N), M₆C and M₂₃C₆ are the primary precipitates in as-cast microstructure. After solution heat treatment, most of carbides dissolve into the matrix except a few fine Ti(C,N) within grains. During long-term aging at 700 °C, the phase precipitation behaviors of the alloy are characterized as follows: (1) M₂₃C₆ carbides at grain boundaries (GBs) transform from film-like shape to cellular shape and gradually coarsen due to the decrease of the surface energy and element aggregation to GBs; (2) M₂₃C₆ carbides within grains have a bar-like morphology with a preferential growth direction [110] and have a cube-on-cube coherent orientation relationship with the matrix γ; (3) γ′ particles inhibit the coarsening of M₂₃C₆ within grains by constraining the diffusion of formation elements. Furthermore, the tensile strength of the alloy obviously increases, but the ductility significantly decreases after the aging for 5000 h. The alloy has a relatively stable microstructure which guarantees the excellent tensile properties during long-term aging.     

Principle and realization of improving shape memory effect in Fe–Mn–Si–Cr–Ni alloy through aligned precipitations of second-phase particles

A principle that the shape memory effect of Fe–Mn–Si–Cr–Ni alloys can be remarkably improved through aligned precipitations of second-phase particles has been proposed and realized through ageing after pre-deformation at room temperature. A 79% shape recovery of an initial 5% strain in Fe–13.53Mn–4.86Si–8.16Cr–3.82Ni–0.16C alloy was attained by ageing at 1073 K after 10–20% tensile pre-deformation at room temperature. Transmission electron microscopy and in situ scanning electron microscopy observations showed that the aligned Cr₂₃C₆ particles were produced by directional interfaces resulting from stress-induced martensite. The aligned particles subdivided grains into even smaller domains, thus reducing and even suppressing the collisions between martensite bands belonging to different smaller domains. The aligned particles caused the stress-induced martensite to form in domains. It is expected that through ageing after moderate pre-deformation, other aligned carbides and nitrides can be attained and the shape memory effect improved further.     

Effect of Post-weld Heat Treatment on the Microstructure and Corrosion Resistance of Deposited Metal of a HighChromium Nickel-Based Alloy

The evolution of Cr_(23)C_6 carbides in the deposited metal(DM) of a high-chromium nickel-based alloy was investigated after the post-weld heat treatment(PWHT) at 650,750,850,and 950 ℃,respectively.With the increase in temperature,the morphology of the Cr_(23)C_6 carbides at the grain boundaries was transformed from the continuous lamellarlike to the semi-continuous rod-like and then to the discontinuous granular.Besides,the needle-like Cr_(23)C_6 carbides precipitated from γ matrix after PWHT at 850 ℃.The coarsening kinetics of the needle-like Cr_(23)C_6 carbides obeyed the Lifshitz-Slyozov-Wagner law with the growth speed of 4.93 μm~3/h in length and 5.56 × 10~(-3) μm~3/h in width.Moreover,the ratio of the carbide length to width increased rapidly at first and then flattened as the holding time increased to 850 ℃.The results of electrochemical corrosion experiment indicated that the needled-like Cr_(23)C_6 carbides impaired the corrosion resistance of DM due to the formation of chromium depletion around the carbides.     

Remarkable improvement of shape memory effect in Fe–Mn–Si–Cr–Ni–C alloy by ageing with deformation

The effects of ageing with and without deformation on shape memory effect and microstructures in Fe–14.8Mn–4.78Si–7.95Cr–4.16Ni–0.18C alloy were investigated. The shape memory effect after the ageing with deformation is much greater than that after ageing without deformation. The reason is that carbides after ageing with deformation is much smaller and lie mainly at grain boundaries.     

电脉冲处理对不同预变形量Fe17Mn5Si8Cr5Ni0.5NbC合金NbC析出相与形状记忆效应的影响(英文)

为进一步提高铁基形状记忆合金的记忆效应并改善处理技术,研究了电脉冲处理对不同预变形量Fe17Mn5Si8Cr5Ni0.5NbC合金性能的影响。结果表明:当预变形量低于 10%时,电脉冲处理后合金的形状回复率随着预变形量的增大而增大,且最大值比800 °C热处理的合金高 8%左右。与热处理状态相比,当预变形量低于10%时,随着预变形量的增大,电脉冲处理诱导出NbC颗粒的数量更多、尺寸更小、析出速度更快,进而有效改善合金的记忆性能。     

Effects of amount of pre-deformation on precipitation of NbC particles and shape memory effect of Fe17Mn5Si8Cr5Ni0.5NbC alloy during electropulsing treatment

To further enhance shape memory effect (SME) and improve treatment technique in Fe-based shape memory alloys, an Fe17Mn5Si8Cr5Ni0.5NbC alloy was subjected to electropulsing treatment after pre-deformation. The results show that the shape recovery ratio increases with the amount of pre-deformation up to 10%. The maximum shape recovery ratio after electropulsing treatment is 8% greater than that after ageing at 1073 K. The number of NbC particles induced by electropulsing treatment is increased and the size of the particles is decreased with the amount of tensile pre-deformation up to 10%, and NbC carbides are precipitated more quickly through electropulsing treatment than by ageing.     

Co-Cr-W-Ni合金中碳化物析出机制的研究

Co-Cr-W-Ni合金中碳化物的类型和析出机制对合金的力学性能影响显著,因此,本文用XRD、SEM-EBSD和TEM技术研究了Co-Cr-W-Ni合金时效后碳化物的析出类型、分布特征和析出机制。实验结果表明,Co-Cr-W-Ni合金中碳化物的主要类型为M₇C₃、M₆C和M₂₃C₆;M₂₃C₆型碳化物主要分布于孪晶与g相晶粒的三叉交界处,与基体g相是立方-立方的取向关系;M₆C型碳化物退化分解并原位析出M₇C₃型碳化物是Co-Cr-W-Ni合金中一种重要的碳化物析出机制。     

长期时效对GH4586B合金组织及高温拉伸性能的影响

研究了一种新型镍基合金在750℃下长期时效1500 h过程中的组织变化及其对750℃高温拉伸性能的影响。利用扫描电子显微镜对合金长期时效过程中的显微组织和高温拉伸断口进行了观察分析。结果表明:GH4586B合金在时效过程中晶界和晶内均有碳化物析出,晶界析出碳化物的形貌呈弥散的颗粒状,并随时效时间的延长有逐步转变为连续链状的趋势,同时合金内未见有害拓扑密堆(TCP)相析出;合金在750℃高温下拉伸,随着时效时间的延长合金的强度和塑性在500 h时表现为峰值,且随着时效时间的延长略有降低,这与晶界析出碳化物的形貌、分布、数量直接相关;通过750℃高温拉伸断口的形貌分析,合金断裂均具有塑性断裂特征。     

Ageing behavior study of 5Cr–0.5Mo steel by magnetic Barkhausen emissions and magnetic hysteresis loop techniques

Magnetic hysteresis loop and Barkhausen emissions were recorded and analysed for 5Cr–0.5Mo steel after ageing at 600 °C for various lengths of time. At the initial stage of ageing the interstitial carbon diffuses towards the grain boundary making the matrix magnetically softer. During this stage, extending up to 200 h of ageing, magnetic softness was found to be increasing. This was associated with a decrease in coercivity and increase in Barkhausen voltage. Beyond 200 h of ageing the precipitation of alloy carbides attain subsequent growth, making the material magnetically harder. The evolution of carbides was studied using SEM-EDAX analysis. It was observed that most of the carbides transformed into M₂₃C₆ type after ageing for 400 h.     

Alloy carbide precipitation in tempered 2.25 Cr–Mo steel under high magnetic field

The influence of a high magnetic field on carbide precipitation during the tempering of a 2.25 Cr–Mo steel was investigated by means of transmission electron microscopy. As-quenched specimens were tempered at 200, 550 and 700 °C for various times in the absence and presence of a 12 T magnetic field. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M₂₃C₆ carbides at low temperature (200 °C) and M₇C₃ and M₂₃C₆ carbides at intermediate temperature (550 °C). The increased Fe content in the M₂₃C₆ and M₇C₃ carbide significantly increases the magnetization. The magnetic Gibbs free energy, which influenced the alloy carbide precipitation behavior, was considered to be mainly determined by the intrinsic magnetization energy for M₂₃C₆ and M₇C₃ carbides. With the increase of the tempering temperature (700 °C), there was no pronounced effect of the high magnetic field on the precipitation sequence and the concentration of substitutional solute atoms in paramagnetic carbides. The investigation of alloy carbide precipitation under high magnetic fields could contribute to a better understanding of phase transformation of alloy carbides and to the heat treatment and fabrication of heat-resistant steels.     

Precipitation related anomalies in kinetics of phosphorus grain boundary segregation in low alloy steels

It has been shown that particles of M₆C in Cr–Mo–V low alloy steels can influence phosphorus grain boundary segregation in a similar manner to Laves phase particles in 12CrMoV steel. The influence of these particles arises from their ability to dissolve non- metallic elements such as phosphorus and silicon. As phosphorus is progressively segregated to the grain boundaries during prolonged ageing, the precipitation of M₆C particles leads to an anomalous decrease in the phosphorus grain boundary concentration as the ageing time is extended. This phenomenon originally observed for the Laves phase in long-term aged 12CrMoV steel at temperatures of 753, 773, and 803 K has now been observed for M₆C carbide in a 2.5Cr–0.4Mo–0.25V low alloy steel aged at 853 K.     

固溶处理对53Cr21Mn9Ni4N耐热钢组织及碳化物的影响

利用FactSage软件中的FSstel数据库对53Cr21Mn9Ni4N耐热钢的相图进行计算,分析了氮元素对凝固及冷却过程中相变及析出相的影响,得到了53Cr21Mn9Ni4N耐热钢平衡凝固及冷却相变路径图,并用OM、SEM、XRD、EDS等对53Cr21Mn9Ni4N耐热钢在1200 ℃固溶3、10、20、40和60 min后的显微组织及碳化物演变规律进行了研究。结果表明,53Cr21Mn9Ni4N耐热钢由1600 ℃平衡冷却至300 ℃的过程中完整的平衡相变路径为:液相+气体→液相→液相+δ铁素体→液相+δ铁素体+奥氏体→液相+奥氏体→奥氏体→奥氏体+M₂₃C₆→奥氏体+M₂(C,N)+M₂₃C₆→奥氏体+M₂(C,N)+M₂₃C₆+α铁素体→奥氏体+M₂(C,N)+M₂₃C₆+α铁素体+σ相。M₂₃C₆的析出温度随着氮含量的增加而降低,M₂(C,N)的析出物温度随着氮含量的增加而升高,M₂₃C₆会因M₂(C,N)的析出受到抑制。53Cr21Mn9Ni4N耐热钢的铸态组织非常不均匀,奥氏体呈树枝晶状生长,枝晶间析出大量层片状碳化物。随着固溶时间的增加,分布在枝晶间的层片状碳化物逐渐变成块状及短棒状,碳化物的数量逐渐减少,粗壮的树枝晶也逐渐变得细小。53Cr21Mn9Ni4N耐热钢在1200 ℃固溶后的组织及碳化物均得到明显改善。     

铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ＡＴＥＭ研究了铁基多元合金ＦｅＣｒＷＮｉＣ激光熔覆层的微观组织、亚稳相结构特征以及高温时效时的亚稳相转变机制。结果表明组织为亚共晶组织,即γ＋（γ＋Ｍ７Ｃ３）,γ奥氏体为具有较高合金度的过饱和亚稳相,Ｍ７Ｃ３（Ｍ为Ｃｒ,Ｆｅ,Ｗ）为六方结构的Ｃｒ基亚稳合金碳化物。熔覆组织在高温时效时存在两类碳化物形成机制,即亚稳γ中析出Ｍ２３Ｃ６、Ｍ２Ｃ与ＭＣ碳化物以及Ｍ７Ｃ３→Ｍ２３Ｃ６与Ｍ７Ｃ３→Ｍ６Ｃ的碳化物原位转变机制。熔覆组织具有较高的显微硬度并存在显著的二次硬化特征     

A Novel Method to Calculate the Carbides Fraction from Dilatometric Measurements During Cooling in Hot-Work Tool Steel

Dilatometry is a useful technique to obtain experimental data concerning transformation. In this paper, a dilation conversional model was established to calculate carbides fraction in AISI H13 hot-work tool steel based on the measured length changes. After carbides precipitation, the alloy contents in the matrix changed. In the usual models, the content of carbon atoms after precipitation is considered as the only element that affects the lattice constant and the content of the alloy elements such as Cr, Mo, Mn, V are often ignored. In the model introduced in this paper, the alloying elements (Cr, Mo, Mn, V) changes caused by carbides precipitation are incorporated. The carbides were identified using scanning electron microscope and transmission electron microscope. The relationship between lattice constant of carbides and temperature are measured by high-temperature X-ray diffraction. The results indicate that the carbides observed in all specimens cooled at different rates are V-rich MC and Cr-rich M₂₃C₆, and most of them are V-rich MC, only very few are Cr-rich M₂₃C₆. The model including the effects of substitutional alloying elements shows a good improvement on carbides fraction predictions. In addition, lower cooling rate advances the carbides precipitation for AISI H13 specimens. The results between experiments and mathematical model agree well.     

GH3230合金M23C6型碳化物的析出行为

研究了固溶态GH3230合金在800~1100 ℃时效不同时间下的碳化物析出行为。结果表明:GH3230合金固溶态组织主要为γ相+初生粒状碳化物M₆C+少量晶界粒状碳化物M₂₃C₆。试验合金在800~1100 ℃短时时效后,晶界和晶内析出的碳化物主要为M₂₃C₆型。其中晶界粒状M₂₃C₆型碳化物有沿着晶内长大的倾向,并逐渐变成胞状碳化物。在同一时效温度下,晶内碳化物析出数量会随着时效时间的增加而增加,此后会逐渐回溶,回溶开始的时间会随着时效温度的提高而逐渐提前。     

Analytical electron microscopy of C-free and C-containing Ti–15–3

Optical microscopy, analytical scanning and transmission electron microscopy have been used to interpret the influence of C on the ageing response of Ti–15–3 (Ti–15V–3Al–3Sn–3Cr (wt.%)). It has been found that the addition of carbon reduces the extent of oxygen segregation to grain boundaries and thus reduces the tendency for grain boundary alpha to form during ageing. The ageing response and the scale of precipitation at 600 °C have been found to depend on the heating rate used. The as-quenched microstructure is characterised by striations typical of pre-martensite-type contrast with a spacing of about 20–25 nm. Diffraction patterns in as-quenched samples show diffuse scattering in addition to the maxima associated with this large spacing. The striations and diffuse scattering anneal out at ageing temperatures above 400 °C. Contrary to earlier work no evidence has been obtained for omega in as-quenched or aged samples. The alpha precipitation is on a finer scale than can be accounted for by the carbides or by the dislocations punched out by the carbides. This conclusion, taken together with the absence of any evidence for omega, leads to the view that the presence of carbon in solution, rather than the carbides, limits diffusion of oxygen and provides additional nucleation sites for alpha – perhaps through vacancy–carbon–oxygen complexes.     

直流电对7B04铝合金固溶与时效组织和性能的影响

本文采用拉伸试验、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等手段,研究了7B04铝合金在施加和不施加直流电条件下,经470℃固溶和100-140℃时效处理后的组织和力学性能。与传统的T6处理(470 oC/30 min+120 oC/24h)相比,固溶和/或时效处理时施加500A的电流,可显著提高GPII区的析出密度,进而提高峰时效状态下的拉伸强度和延伸率。固溶过程中施加直流电可将随后时效合金达到峰值强度的时间明显缩短12h。