厚板铝合金搅拌摩擦焊接头显微组织与力学性能

对14 mm厚板铝合金搅拌摩擦焊(FSW)接头焊核区微观组织,整体和分层切片力学性能进行了研究.结果表明,当旋转速度为400 r/min,焊接速度为60-100 mm/min时,接头抗拉强度σb、屈服强度σ0.2和延伸率δ随焊速的升高而降低.焊缝分层切片的σb,σ0.2和δ上部最高,分别达到了186.7 MPa,100.3 MPa和14.1%;下部最低,分别为157.5 MPa,80.2 MPa和10.1%.微观断口中存在大量的网状韧窝,切片上部韧窝最深,焊缝根部可见沿晶界的二次裂纹和浅韧窝.显微硬度分布为焊缝上部高于下部,沿焊缝中心呈不对称分布.焊核区上部等轴再结晶晶粒尺寸大于焊缝下部.焊核区上部的第二相粒子相对下部更均匀和细小,强化作用增强.     

镁合金AZ91D焊接接头组织与性能

在镁合金(AZ91D)TIG焊接头中,同质焊缝的相组成主要为α-Mg和β-Al12Mg17;β-Al12Mg17非连续地分布于α-Mg的晶界;β-Al12Mg17的体积分数为7.3%.焊接热影响区(特别是近缝区)最突出的显微组织特点是晶粒粗化和连续分布于晶界的β-Al12Mg17金属间化合物.由于晶粒细化焊缝区硬度值高于母材,而热影响区的硬度值则明显低于母材.与母材相比(σb=156 MPa,δ=4.8%),同质焊缝金属有更高的力学性能(σb=192 MPa,δ=4.9%).焊接接头的力学性能明显低于母材,接头强度为母材强度的69%;接头塑性为母材的72%;断裂主要发生在热影响区的近缝区.降低焊接热输入有利于改善焊接接头的力学性能.     

激光增材制造GH3625高温合金激光焊接头组织及力学性能

对激光增材制造GH3625高温合金进行激光对接焊实验,分析了焊接接头的显微组织演变规律和力学性能。结果表明,在热影响区,仅在上层晶界处析出大量Laves相,导致晶界发生明显粗化。沿焊缝上层至下层,熔合区和中间区由上层的胞状晶、柱状晶和等轴细晶逐渐转变为下层的柱状晶,且紧贴熔合线生长的等轴细晶的数量逐渐增多,中心区均为树枝晶。细小颗粒状γ′相弥散分布于焊缝;大量Laves相在中间区枝晶间析出,且形态由上层的条状逐渐转变为下层的颗粒状。接头抗拉强度为872MPa,达到母材抗拉强度的98.2%,伸长率达到母材的90.7%。接头断面近似呈45°斜面,断裂形式为脆性和韧性混合断裂方式。     

焊后热处理对铝锂合金激光焊接头微观组织的影响

采用Nd:YAG激光对3 mm厚5A90铝锂合金薄板进行激光焊接,焊后对接头进行了固溶-时效处理,对热处理前后接头微观组织和显微硬度的分布进行了对比研究。研究结果表明,焊态5A90铝锂合金激光焊焊缝组织晶粒形态为等轴枝晶,未观察到强化相;经过焊后处理后,接头不同区域组织均呈现明显的晶界,焊缝金属晶粒形态转变为等轴晶,焊缝组织均匀性得到改善,并且焊缝金属晶粒内部弥散析出较多的δ'强化相。焊态下5A90铝锂合金激光焊焊缝的显微硬度低于母材,焊后热处理使焊缝金属中δ'强化相析出从而使焊缝的硬度显著提高。     

BTW热轧中锰钢MAG焊接性能研究

研究了BTW热轧中锰钢MAG焊焊接性能,利用金相显微镜、拉伸试验机、冲击试验机、维氏硬度计等分析了焊接接头组织结构、力学性能等。实验结果表明,焊接接头平整、光滑,未发现夹渣、宏观裂纹等焊接缺陷。焊缝室温组织由铁素体和奥氏体组成,热影响区奥氏体晶界和晶粒内部有碳化物析出。焊接接头力学性能高于母材,室温抗拉强度在750 MPa以上,焊缝区冲击功为116 J。焊接接头热影响区显微硬度高于焊缝显微硬度,焊缝清根部显微硬度高于焊缝表面显微硬度。清根处焊缝显微硬度为290 HV,热影响区显微硬度在300 HV以上,焊接接头在(160 mm,180°)的弯曲试验中表现为合格。     

厚板铝合金搅拌摩擦焊接头不同状态微观组织与力学性能

对14 mm厚2219～O铝合金板进行了搅拌摩擦焊接,研究了无缺陷、有缺陷和经焊后热处理的接头分层切片的微观组织、力学性能和断裂方式.结果表明:无缺陷接头的抗拉强度σb和屈服强度σMM0.2分别从上部的160.8和96.8 MPa下降至底部的146和86 MPa;有缺陷接头的σb和σ0.2分别从上部的132.9和94 MPa下降至底部的126和78.8 MPa;经焊后热处理的试样中部的σb最高,达到243.8 MPa,而上部的σ0.2最高,为123.3 MPa;延伸率δ则依次升高,无缺陷,有缺陷和热处理后接头的δ分别由上部的6.7%,4.8%和7.5%升高至底部的10.1%,8.5%和14%.经焊后热处理的接头焊核区晶粒沿厚度方向更均匀和细小,力学性能明显提高,并以韧性断裂为主,显微硬度波动很小.对于有缺陷接头,焊接缺陷严重降低了接头的力学性能,主要以韧-脆混合方式断裂,各分层的显微硬度均低于无缺陷接头.     

20CrMn2SiMo钢与20CrNi3Mo钢摩擦焊接头的组织和性能

研究了20CrMn2SiMo钢与20CrNi3Mo钢摩擦焊焊接接头的组织和力学性能。结果表明,未进行热处理时,其焊缝区显微硬度最高,热影响区其次,母材硬度最低;热处理后,焊缝和基体组织均为板条状贝氏体和马氏体以及少量的残余奥氏体,焊缝区和基体硬度基本相同;热处理后的焊接接头具有良好的强韧性:σb=1351MPa,δ5=11%,ψ=43%。     

6061铝合金激光填丝焊接接头组织与性能

以2mm厚6061-T651铝合金的激光填丝焊对接接头为研究对象,利用光学显微镜、SEM、EDS、显微硬度计分析了优化试验条件下焊接接头的显微组织、析出相形态、分布及成分,并测试了接头的显微硬度。分析结果表明,由于激光焊具有能量集中、热输入小的特点,焊缝晶粒细小且热影响区较窄。在焊缝内部,大量条状和颗粒状的析出相均匀分布于其中,对焊缝的力学性能有显著影响。此外,焊后焊缝区的硬度远高于热影响区和母材,这与焊缝中大量析出的增强相、硅硬质点等因素有关。     

新型Al-Zn-Mg-Cu合金TIG焊接头组织与性能

对一种Al-Zn-Mg-Cu-Mn-Zr-Er合金薄板进行了全自动TIG填丝焊接,观察接头微观组织形貌,并测试其力学性能。结果显示焊缝未出现典型的联生结晶形貌,而是由等轴细晶粒层和大量等轴树枝晶构成,在晶界或枝晶间断续分布复合T(AlZnMgCu)相;焊接热影响区因沉淀相变化,硬度值不同,分为近缝的固溶区和远缝的过时效区,晶粒保持与母材相同的拉长形貌,未见明显长大;接头横截面的显微硬度最低值在焊缝,HV约为1200 MPa,母材显微硬度HV约为1840 MPa,接头抗拉强度为421.75 MPa,达到母材的65.08%,拉伸断裂位置处于焊缝中,断口形貌为典型的韧性断裂,等轴韧窝底部存在破碎的第二相颗粒,其成分与焊缝中复合T相基本一致。     

TC21钛合金线性摩擦焊接头组织及性能分析

本文对TC21钛合金进行线性摩擦焊接试验,采用OM、SEM等测试手段对接头各区域显微组织演变规律进行了分析,并通过显微硬度仪和电子万能试验机对接头显微硬度及拉伸性能进行测试。结果表明：TC21钛合金线性摩擦焊可以得到良好的焊接接头,接头明显分为母材区、热力影响区和焊缝区；焊接过程中焊缝区发生了相变及动态再结晶过程,形成细小的再结晶晶粒,板条状α相在晶界处析出,针状马氏体α′相在晶粒内部析出,并有少量的残余α相保留至室温；热力影响区主要以变形α相为主,随着向两侧母材靠近,再结晶程度逐渐减弱,α相比例逐渐增加。由于飞边形成阶段及焊后冷却速率大小不同,导致沿着焊缝中心向飞边端部靠近,晶粒尺寸逐渐变大。TC21钛合金线性摩擦焊接头显微硬度呈拱形分布,焊缝中心显微硬度值达到最大值460HV,拉伸性能测试结果表明,接头强度与母材相当。     

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。     

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.     

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.     

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.     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.     

Structural Optimization of Electromagnetic Swirling Flow in Nozzle of Slab Continuous Casting

During the slab continuous casting process, the flow field of molten steel in the mold plays a decisive role in the quality of the slab. In this paper, electromagnetic swirling flow in nozzle technology is proposed to control the flow field in mold.This technology can drive molten steel to rotate inside the submerged entry nozzle by electromagnetic force, thereby controlling the flow field. This research shows that it can reduce the impact of molten steel on the bottom of nozzle and partly reduce the negative pressure at the upper part of nozzle outlet which is even eliminated by optimizing the structure and angle of nozzle. The area of heat flux of the mold wall becomes larger, and the crest value of heat flux gets lower than that without swirling in nozzle and any nozzle optimization. The meniscus fluctuates smoothly, and the flow velocity at the top surface is within a reasonable range. The temperature field distribution in the mold is uniform which was beneficial to the growth of equiaxed crystal and decreased element segregation.