热等静压处理对选区激光熔化成形Inconel 718合金各向组织及力学性能的影响

目的 研究热等静压处理对选区激光熔化（SLM）成形不同沉积方向Inconel 718合金试样显微组织和力学性能的影响规律,提升Inconel718合金的综合力学性能。方法 采用SLM技术制备平行沉积方向和垂直沉积方向的Inconel 718合金试样,并对试样进行热等静压（HIP）处理和热等静压+固溶时效（HIP+HT）处理。利用金相显微镜（OM）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射仪（XRD）和电子背散射衍射（EBSD）,对合金的显微组织、断口形貌、物相组成、晶粒形貌及取向进行分析。对试样进行显微硬度和拉伸强度性能测试,对比分析不同沉积方向SLM、HIP及HIP+HT试样的显微硬度、拉伸强度、屈服强度以及断口延伸率。结果 SLM成形的Inconel718合金经热等静处理后,平行方向的晶粒形态由柱状晶转变为等轴晶,晶粒尺寸增大,并伴随有孪晶形成。晶界处的Laves相基本溶解,同时有许多MC碳化物在γ基体中析出。不同处理状态下平行方向试样的拉伸强度、屈服强度和硬度值均小于垂直方向。平行和垂直方向SLM成形件的拉伸强度σb分别为996.3MPa和1051.1MPa...     

Inconel 738合金选区激光熔化成形工艺优化及组织性能的研究

采用SEM、EBSD、OM等方法,研究了激光体能量密度E对SLM成形Inconel 738合金致密度、微观组织和显微硬度影响。研究表明：在SLM成形过程中,激光体能量密度E对试样致密度起决定性作用,随着激光体能量密度的增大,致密度呈现先上升后下降的趋势,并且在65.2 J/mm<sub>3</sub>可以实现最高致密度(99.4％);凝固过程中冷却速率高达2.44×10<sub>5</sub> K/s,SLM成形Inconel 738合金的组织垂直与打印方向和平行与打印方向有明显的各向异性,平行于打印方向的组织呈“棋盘状”形貌,垂直与打印方向为“鱼鳞状”形貌,层与层之间、不同道次之间的熔池搭接区为晶粒细化的胞晶;显微组织表现出明显的织构,随着激光体能量密度的增大,＜001＞方向的织构逐渐增强;试样的硬度随着激光体能量密度的增大而增大,当硬度值超过65.2 J/mm<sub>3</sub>时,SLM成形Inconel 738合金的硬度值超过精铸试样(410 HV),硬度值在各个面上的分布是定向独立的。     

磷硼复合添加对Inconel 718合金铸态组织及均匀化处理参数的影响(英文)

研究磷硼复合添加对Inconel 718高温合金铸态组织及均匀化处理参数的影响。结果表明:磷硼的加入促进块状Laves相的形成。由于硼在最后残余液相中大量富集,形成一种富含Nb、Mo和Cr的含硼相。根据DSC和电子探针分析结果,确定磷硼复合添加Inconel 718高温合金的凝固顺序为L→L+γ→L+γ+MC→L+γ+MC+Laves→γ+MC+Laves+含硼相。由于低熔点含硼相的存在,磷硼复合添加Inconel 718高温合金的均匀化处理温度应比标准Inconel 718合金低至少40°C。     

选区激光熔化成形Inconel 625合金的激光焊接头组织及高温蠕变性能

采用光学显微镜、扫描电镜、X射线衍射仪和能谱仪等对选区激光熔化 (SLM) 成形Inconel 625合金的激光焊接头组织特征及高温蠕变性能进行研究分析. 结果表明,SLM成形Inconel 625合金的激光焊接头质量良好,无明显的制造缺陷存在. SLM成形Inconel 625合金激光焊焊接试样的组织主要由母材区的等轴奥氏体组织以及焊缝区的柱状枝晶组成. 高温蠕变试验结果显示,试样的蠕变时间随着应力的增大急剧下降. 较高的应力水平（200 MPa）对合金在同一温度下的蠕变性能影响很大,会导致蠕变变形直接进入蠕变第三阶段——加速阶段,引发试样较早发生断裂. 断口分析表明,所有试样断裂均发生在母材区或近热影响区,母材区观测有大量二次裂纹,熔覆区未观察到明显裂纹. 蠕变断口形貌呈冰糖块状特征,表明断裂模式主要为沿晶断裂. 高温下晶界滑移引发的形变位移是晶界空洞形核的主要机制.     

激光选区熔化生物医用Ti-6Al-4V合金的弯曲疲劳行为

分析了SLM Ti-6Al-4V合金的弯曲疲劳行为及相应的微观组织和断口形貌,设置与SLM试样化学成分相同的轧制态Ti-6Al-4V合金进行对比研究.采用X射线衍射(XRD)、结合电子背散射衍射(EBSD)的扫描电子显微镜(SEM)对合金的微观组织进行分析.结果表明,三点弯曲疲劳裂纹起始于准解理断裂表面附近的应力集中,随后向内扩展.SLM成形Ti-6Al-4V合金的弯曲疲劳寿命高于轧制成形Ti-6Al-4V合金,SLM Ti-6Al-4V合金内部孔洞缺陷导致表面附近应力集中,促进疲劳裂纹形核;而SLM Ti-6Al-4V合金中随机取向的α+β晶粒、二次裂纹和孔洞延缓了裂纹扩展,提高了疲劳寿命.对于轧制态Ti-6Al-4V合金,由大量近似取向α晶粒组成的宏观区引起应力集中,形成微裂纹,导致疲劳裂纹形核,而且宏观区对裂纹扩展的阻碍作用较小,不利于材料的疲劳寿命.     

去应力退火SLM成形Inconel 738合金组织和性能演变

由于选区激光熔化(SLM) 制备Inconel 738合金过程中快速熔化凝固的特点，成形合金中存在较高的残余应力，影响合金的服役。本文主要研究了不同退火温度 (700 ~900 ℃)下保温24 h后合金中残余应力、析出相行为、组织和性能演变。结果表明：退火过程中，组织演变机制为静态回复，发生位错迁移和晶界类型转变；形成的短棒状γ"相(240~440 nm)和球状γ"相(50~250 nm)；晶界碳化物分布由点状向连续状转变，类型由MC向M23C6转变；800 ℃退火后，残余应力由380.94 MPa(沉积态)下降至-66.7 MPa，残余应力得到释放；随着退火温度升高，硬度和抗拉强度先增大后减小，延伸率先减小后增加，800 ℃退火后，合金具有最高的硬度、抗拉强度 (581.2 HV、1330 MPa)为铸造性能(410 HV、945 MPa)的1.42倍、1.41倍。     

热处理工艺对316L不锈钢粉末激光选区熔化成形的残余应力及组织的影响

对316L不锈钢粉末进行了激光选区熔化(Selective laser melting, SLM)成形,采用光学显微镜、扫描电镜和电子背散射衍射技术等研究了其热处理前后的残余应力及组织的变化。结果表明:热处理前试样的残余应力值从上表层向靠近基板的底层逐渐增大,残余应力较大;热处理后试样的残余应力降低,转变为较小压应力的稳定态;SLM直接成形试样的晶粒非常细小、晶粒尺寸为1～2μm,以月牙状铁素体组织为主,晶面位向差异与晶界间距大,相互之间形成了不平衡态的熔融热应力,导致产生了较大残余应力;固溶+时效热处理后,合金元素进行固溶重晶,晶粒长大,晶粒尺寸达到10～30μm,形成椭圆形的奥氏体组织,晶面位向差减小,为较均匀的各向同性配置,这种重晶促进了应力释放,残余应力明显降低或消除。     

基于扫描间距调控Inconel 738合金的微观组织和力学性能

采用EBSD技术系统地研究了扫描间距h对选区激光熔化(SLM)成形Inconel 738合金微观组织、动态再结晶行为、织构演变和力学性能的影响。研究表明,随着h的增加,平行于沉积方向的细长柱状晶晶粒长/径比减小,晶粒的形貌由粗大的细长柱状晶向细小的等轴晶转变,晶粒的取向变得更加随机;随着h的增加,动态再结晶体积分数增加,再结晶区域位错密度和应变低于未再结晶区域;随着h的增加,其铸造织构的类型发生变化,织构主要由Rotated-Goss织构{110}110转变为Rotated-Goss织构{110}110+Cube织构{001}100,Cube织构的强度逐渐增强,而Rotated-Goss织构的强度逐渐减弱;此外,通过选择合适的扫描间距(h=70μm),沉积态Inconel 738合金可获得优异室温力学性能(σ_y=933 MPa,σ_(uts)=1209 MPa,ε_f=38%),达到良好的强度与塑性匹配。     

不同工艺条件下A356合金的力学性能、微观组织和热疲劳特性研究

研究了不同工艺条件下A356微观组织、力学性能和热疲劳特性。结果表明:细化变质+微合金化+T6工艺的A356合金力学性能、热疲劳性能最优。热疲劳裂纹萌生期为沿晶生长,扩展期为沿晶+穿晶混合生长。裂纹扩展速率呈先增加后减缓的趋势,未脱落的Al_2Cu相、裂纹分叉与二次裂纹的产生均会减缓裂纹扩展速率。循环初期形成的氧化膜可抵消部分拉应力,阻碍氧化腐蚀;后期氧化膜遭到破坏,氧化腐蚀加剧,裂纹扩展加速。裂纹生长过程:位错滑移→空位→微坑→微裂纹→尖端闭合、张开→扩展。     

激光选区熔化成形K4202镍基铸造高温合金的组织和性能

针对激光选区熔化(selective laser melting,SLM)制造K4202合金复杂金属零件在航空航天等领域的应用需求,以K4202合金粉末为材料,研究了该合金的SLM成形工艺、成形态和热处理后的显微组织和力学性能.结果表明,K4202合金SLM成形试样显微组织由树枝晶和等轴晶构成,树枝晶生长方向多与熔池边界近似垂直.固溶+时效处理后,由于再结晶的发生,SLM成形所形成的树枝晶结构完全消失,同时晶界和晶内有金属碳化物析出.时效处理后的组织与SLM成形态相比,变化并不明显,其树枝晶结构保存较完整,晶界处同样有碳化物析出.SLM成形试样的拉伸性能优于传统铸造方法,通过固溶+时效处理和时效处理,试样的屈服强度、抗拉强度均提升显著,但塑性下降明显,其中时效处理后的拉伸强度最高.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.