Observation of etch pits in Fe-36wt%Ni Invar alloy

To indirectly investigate the dislocation behavior of Fe-36wt%Ni Invar alloy by the etch pit method, polished Invar specimens were etched by a solution containing 4 g copper sulfate, 20 mL hydrochloric acid, and 20 mL deionized water for 2 min. Etch pits in the etched surfaces were observed. All the etch pits in one specific grain exhibited similar shapes, which are closely related to the grain orienta-tions. These etch pits were characterized as dislocation etch pits. It was observed that etch pits arranged along grain boundaries, gathered at grain tips and strip-like etch pit clusters passed through a number of grains in the pure Invar specimens. After the addition of a small amount of alloying elements, the identification of a single dislocation etch pit is challenging compared with the pure Invar alloy. Thus, the observation of etch pits facilitates the investigation on the dislocation behavior of the pure Invar alloy. In addition, alloying elements may affect the densities and sizes of etch pits.

The numerical simulation of laser-MIG hybrid welding for Invar alloy

Composites are widely applied to the manufacturing of aircraft in aviation. Forming of large-scale composite component in aircraft requires the corresponding mold with precise size. The laser-MIG hybrid welding has a significant advantage in the manufacturing of Invar mold for aircraft composites. This paper mainly introduces the application of the laser-MIG hybrid welding,and the distribution of thermal field and flow field on the Invar alloy laser-MIG hybrid three-layer welding is analyzed and discussed specifically.

THERMODYNAMICS OF MARTENSITIC TRANSFORMATION IN Fe-Mn-C AND Fe-Ni-C ALLOYS

A Central Atom Model is introduced and the LFG and Hsu models are modified in order to evaluate the driving force for the martensitic transformation in Fe-Mn-C and Fe-Ni-C al- loys.The results show that the relationship between the driving force and the yield strength of austenite at Ms temperature,σ_(0.2)~γ/M_s,fits Hsu's formula;ΔG~=2.1σ_(0.2)~γ/M_s+907 J/mol.The M_s temperatures of Fe-Mn-C and Fe-Ni-C alloys are also calculated.The calculated results are in good agreement with experimental values.

Quantitative research on the heat affected zone of weave bead welding for Invar alloy

Quantitative research on the heat affected zone （ HAZ） o f weave bead welding （ WBW） joint fo r Invar alloy is carried out in this paper. Based on the morphology and related data analysis of the weld seam, the width difference o f each layer and the forming mechanism are analyzed. Results show that the bottom layer （ Layer 1 ） has the widest HAZ and the smallest fluctuation, which reaches 1 200 ｜jLm. HAZ width o f layer 2 to 5 is relatively narrower which is basically below 600 jjim, while the amplitude fluctuation is greater. The main reason lies in the welding path. The long straight welding without weave causes the base metal near the groove fully melts which causes by the long straight welding without weave, while welding with weave leads to the uneven and inadequate melting of metal near groove.

Electrochemical preparation of the Fe-Ni36 Invar alloy from a mixed oxides precursor in molten carbonates

The Fe-Ni36 alloy was prepared via the one-step electrolysis of a mixed oxides precursor in a molten Na2CO3-K2CO3 eutectic melt at 750℃,where porous Fe_(2)O_(3)-NiO pellets served as the cathode and the Ni10 Cu11 Fe alloy was an inert anode.During the electrolysis,Ni O was preferentially electro-reduced to Ni,then Fe_(2)O_(3)was reduced and simultaneously alloyed with nickel to form the Fe-Ni36 alloy.Different cell voltages were applied to optimize the electrolytic conditions,and a relatively low energy consumption of 2.48 k W·h·kg^(-1) for production of Fe Ni36 alloy was achieved under 1.9 V with a high current efficiency of 94.6%.The particle size of the alloy was found to be much smaller than that of the individual metal.This process provides a low-carbon technology for preparing the Fe-Ni36 alloy via molten carbonates electrolysis.

ANOMALOUS EFFECT OF PRESSURE ON THE CURIE TEMPERATURE IN MECHANICALLY ALLOYED Fe-Ni INVAR

Measurements of magnetic susceptibility in mechanically alloyed Fe-Ni Invar alloys were taken under pressures up to 7.5GPa. The rate of decrease in the Curie temperature for 700℃ annealed specimen was larger than that annealed at 1000℃. This result can be explained by considering the fact that the width of the concentration fluctuation becomes larger in the specimen annealed at lower temperature.

Investigation on the hot ductility of Fe- 36Ni invar alloy with cerium addition

The hot ductility of Fe-36Ni invar alloy with different additions of the element cerium was investigated using a Gleeble-3800 thermal-mechanical simulator over the temperature range 850 - 1 050℃, and the improvement mechanism of the hot ductility was analyzed using a combination of SEM, EDS, and OM. The results indicated that Fe-36Ni invar alloy exhibited poor hot ductility below 1 050℃, which was mainly attributed to weak grain boundaries and the action of grain boundary sliding. However, the alloys with cerium contents of 0. 016% and 0.024% both demonstrated substantial improvement in the hot ductility over the entire testing temperature range. The observed improvement of the hot ductility of the alloy with 0. 016% cerium at 950 ~C and the alloy with 0.024% cerium at 900℃ was associated mainly with the grain boundary strengthening and the restriction of the grain boundary sliding because the addition of cerium reduced the segregation of sulfur at grain boundaries and refined the grain structure. The occurrence and acceleration of dynamic recrystallization were found to be responsible for the high hot ductility of the alloy with 0.016% cerium at 1 000℃ and the alloy with 0. 024% cerium at 950 - 1 000℃ as a result of the refinement of the grain structure by addition of cerium.

精细金属掩模板用近零夹杂Invar合金制备技术

Invar合金是制备精细金属掩模板(Fine Metal Mask,简称FMM)的重要基材,其纯净度直接影响FMM的质量以及有机发光二极管(Organic Light EmittingDiode,简称OLED)技术的发展水平。首先概述了FMM的主要制备技术,介绍了对FMM基材Invar合金的质量要求,并对国产Invar合金箔和国外进口Invar合金箔内的夹杂物进行了表征分析。结果表明,国产Invar合金箔的纯净度与进口Invar合金箔相比,仍存在很大的差距,主要体现在夹杂物的尺寸和数量等方面。为实现OLED配套产业全国产化,攻克Invar合金的近零夹杂难题,开发新型制备技术是关键突破点。最后详细论述了超重力技术在Invar合金除杂方面的研究成果和电铸Invar合金箔应用的可行性,并指出超重力技术和电铸技术有望解决近零夹杂金属材料的制备难题。

The effect of rare earths on the solidification structure of Fe-36Ni invar alloy

The effect of Ce, La and mischmetal on the solidification structure of Fe-36Ni invar alloy was investigated. The results show that great amounts of high-melting point compounds （ Ce2O3, La202S and （ Ce, La）2O2S ） respectively formed in the alloy with the addition of Ce, La or mischmetal. Based on the theory of lattice misfit, the lattice misfit between the （0001） surfaces of Ce2O3,Ce2O2S and La2O2S and （100） surface of Fe-36Ni invar alloy were 6.21%, 5.77 % and 5.42 %, respectively, which are relatively low. Therefore, Ce2 O3, La2 O2 S and （ Ce, La） 2 O2 S could serve as the core of heterogeneous nucleation, improve the equiaxed grain ratio, reduce the equiaxed grain size and refine the solidification structure of alloy.

Effect of Arc Energy on Morphology and Microstructure of Laser-MIG Hybrid Welded Joints of Invar Alloy

Laser-MIG hybrid welding experiments of 7 mm thick Invar alloy are carried out.The macro appearance of joints is observed and the influence of arc energy on the cross-section morphology is analyzed.The distribution of temperature field is simulated to explain the relationship between heat effect and microstructure.Besides,the average grain size of weld under different arc energies is quantitatively studied.The results indicate that welded joints with uniformity and good formation are obtained.The weld width and the weld seam area increase and the depth to width ratio decreases with the increase of arc heat input.The transition of columnar crystals to equiaxed crystals is observed from the fusion line to the weld center.It is found that the higher the arc energy,the coarser the columnar crystal.

焊丝成分对国产Invar合金GTAW接头组织差异性的影响

采用钨极惰性气体保护焊(Gas tungsten arc welding,GTAW)工艺完成15 mm厚国产Invar合金的焊接,研究了焊丝成分对接头组织差异性的影响。结果表明:三种焊丝所获得的显微组织均由焊缝边缘垂直于熔合线生长的粗大柱状晶和焊缝中部的等轴晶组成,等轴晶内部的亚晶结构明显细化。使用不同成分焊丝后在焊缝形成的析出相种类、形态与分布位置存在较大差别。采用添加0.40%Ti的焊丝在晶界析出较多规则的块状颗粒,而添加1.42%Nb的焊丝在亚晶界析出白色链状或柱状连续相。析出相不仅能作为异质形核的核心或钉扎晶界的质点细化晶粒,还可以作为沉淀相阻碍位错运动从而提高焊缝强度。试样拉伸结果表明:焊丝加入0.40%Ti、1.42%Nb后,接头的抗拉强度大幅提升,分别达到638.2 MPa和653.5 MPa,相较原始焊丝分别提高60.6%、64.4%。断口形貌表明采用含铌焊丝(1.42%Nb)后断口韧窝尺寸和深度增大,接头断裂模式由脆性断裂转变为韧性断裂,说明Nb元素对Invar合金接头组织细化、力学性能改善具有显著作用。

变形与热处理对Invar合金组织及性能的影响

针对实际生产中Invar合金抗跌落性能差的问题 ,对Invar合金试样进行了不同温度 (80 0℃、90 0℃、10 0 0℃ )的退火、不同变形量的冷变形及不同温度 (5 0 0℃、6 0 0℃ )的二次退火试验 ,并进行了显微组织观察和力学性能试验 ,分析各种工艺参数对Invar合金的组织和性能的影响。结果表明 ,经 80 0℃退火 + 2 3%变形 + 5 0 0℃二次退火处理的Invar合金具有最佳综合性能。

4J42 Invar合金粉末注射成形工艺研究

以羰基Fe，Ni粉为原料，蜡基聚合物为粘结剂，采用粉末注射成形技术制备了4J42 Invar合金零件。研究了粉末注射成形Invar合金的脱脂及烧结工艺。结果显示：“溶剂脱脂＋热脱脂”工艺能有效快速地实现粘结剂的完全脱除；经1350℃氢气烧结，可以获得致密度98．5％，30-300℃内平均热膨胀系数为4．5×10^-6 K^-1、漏气率〈1．4×10^-9 Pa·m^3·s^-1的PIM 4J42 Invar合金。金相显微组织及XRD分析表明合金为单一稳定的奥氏体（γ相）组织。

迈克尔逊干涉仪研究Fe-Ni-Co超因瓦合金的热膨胀性能

采用改装后的迈克尔逊干涉仪测量了不同化学成分的三元Fe-Ni-Co合金和二元Fe-Ni合金在25 - 65℃的热膨胀系数.实验发现,三元Fe64 Ni36-x Cox合金的化学成分对其热膨胀系数有很大的影响,Fe64 Ni31 Co5合金的热膨胀系数最小,达到0.79×10-6/℃;偏离该成分,合金的热膨胀系数升高.二元Fe-Ni合金的化学成分对其热膨胀系数也有很大的影响,Fe65 Ni35合金的热膨胀系数最小,达到1.58×10-6/℃;偏离该成分,合金的热膨胀系数升高.Fe64 Ni31 Co5超因瓦合金的热膨胀系数比Fe65 Ni35因瓦合金更低.Fe-Ni合金的热膨胀系数随Ni含量的变化相对较大;而Fe64 Ni36-x Cox合金的热膨胀系数随Co含量的变化相对较小.

Invar合金电子封装零件的制备及性能

研究了粉末注射成型技术生产Invar合金电子封装零件的工艺.设计一种新型蜡基多聚合物组元粘结剂,其组成：PW,PEG,LDPE,PP,SA的质量分数分别为50 %,20 %,15 %,10 %,5 %.并依其差热分析结果制定了合理的脱脂工艺.在1 350 ℃氢气烧结时,可制备出性能优良的PIM Invar合金电子封装零件,其致密度、抗拉强度、30～300 ℃温度内的平均热膨胀系数α30～300 ℃分别为98.5 %、420 Mpa、4.5×10-6℃-1,其漏气率小于1.4×10-9 Pa·m3·s-1.

Invar 36合金搅拌摩擦焊焊缝的低温韧性

为了研究Invar36合金搅拌摩擦焊焊缝的低温韧性,采用小冲杆试验方法(small punch test)对焊接速度2 mm/s,搅拌头旋转频率200～1 000 r/min的Invar36合金焊缝进行低温(77 K)和室温(298 K)韧性测试.298 K下,所有焊接工艺的焊缝小冲杆试验能均高于母材,焊缝韧性随搅拌头旋转频率的提高而降低.77 K下,搅拌头旋转频率小于等于400 r/min的焊缝的低温韧性明显优于母材.所有焊缝在77 K下的小冲杆试验能均高于298 K下的结果,未发生脆性转变.结果表明,Invar合金搅拌摩擦焊焊缝具有优异的低温韧性,但随着搅拌头旋转频率的提高,焊接热输入增加使焊缝组织粗化,从而导致焊缝韧性降低.

激光加工工艺参数对Invar 36合金表面微织构质量的影响

目的提高微织构的加工效率和加工质量,为改善Invar 36合金的表面性能及微织构加工工艺参数提供理论依据。方法为了保证该研究的合理性和可行性,采用光纤激光加工技术并结合正交试验法研究了激光功率,激光频率,激光扫描速度和扫描次数4种不同加工参数对微织构凹槽表面形貌结构尺寸及加工质量的影响,并通过摩擦学试验方法测试了其对应的摩擦学性能。最后,通过三维形貌测试仪和扫描电子显微镜对微织构加工结果进行测量表征。结果微织构凹槽的加工质量与激光扫描次数和扫描速度的关系更大,随着激光扫描次数的增加,微织构的深度明显增加,但是其宽度逐渐减少。当扫描次数在5~15次时,随着扫描次数的增加,微织构表面及边缘熔融物不规则凸起逐渐平整。激光扫描速度与微织构凹槽的宽度成正比,但是与微织构凹槽的深度及边缘不规则凸起的高度成反比关系。此外,当激光扫描次数为15次,激光扫描速率为400~500μm/s时,加工的微织构表面粗糙度更低,且根据摩擦试验结果,发现该条件下加工的微织构摩擦副的减摩耐磨效果更佳。结论激光扫描次数和激光扫描速度是影响凹槽型微织构加工质量和表面性能的关键因素,试验结果表明在适当的激光加工工艺参数下(P=0.04 W,f=20 kHz,v=500μm/s,n=15)微织构凹槽具有较高的加工质量,从而有效改善Invar 36合金的摩擦学性能,对未来进一步提高Invar 36合金的表面性能及加工质量具有一定的指导意义。

非晶态Fe_（90－x）Co_xZr_（10）合金的Invar效应研究

研究了作晶态Ｆｅ_（９０－ｘ）Ｃｏ_ｘＺｒ_（１０）合金的磁体积效应和广义声子谱．通过热膨胀测量和磁测量给出了自发体积磁致伸缩ωｓ和平均磁矩μ_（ＦｅＣｏ）与平均价电子数Ｎ_（ｅｆｆ）的关系，发现ωｓ的峰值位置与μ_（ＦｅＣｏ）开始急剧下降的位置（Ｎ_（ｅｆｆ）＝８．１－８．２）相对应，从而证实了金属－金属型非晶态因瓦合金中的Ｉｎｖａｒ效应与铁磁态的不稳性有关．用非弹性中子散射方法测量了广义声子谱，从中观察到了与Ｉｎｖａｒ效应相关的声子谱软化现象．

4J32 Invar合金的注射成形

以铁粉、镍粉和钴粉为原料，研究了4J32 Invar合金的注射成彤工艺。选择了一种适合4J32 Invar合金注射成形的粘结剂体系。在烧结温度为1350℃，烧结时间为120min，烧结气氛为H2时，烧结样品的致密度达到97．1％。在低于100℃的范围内，烧结样品的膨胀系数小于0．64×10^-6／K，完全符合低膨胀系数的合金的要求：在20～100℃范围内，其热膨胀系数α≤1.8 ×10^- 6/℃.

4J36 Invar合金注射成形研究

以羰基铁粉及镍粉为原料,多组元蜡基聚合物为粘结剂,对4J36 Invar合金的粉末注射成形工艺及其性能进行了深入研究。结果表明,提高烧结温度或采用合适的烧结气氛都有助于获得高性能的PIM 4J36 Invar合金;在优化烧结工艺条件下,即烧结温度1350℃、烧结时间120min、氢气气氛,合金的致密度达到98.1%,其热膨胀性能低于传统工艺制备的4J36 Invar合金,其室温～100℃温度范围内平均热膨胀系数仅为0.97×10-6℃-1,适应于精密零器件的制备。金相显微组织及XRD分析表明合金为单一稳定的奥氏体(γ相)组织。