固溶热处理对热旋锻粉末冶金Ti-Nb-Ta-Zr-O合金微观结构与力学性能的影响

研究固溶热处理对采用热旋锻加工制备的粉末冶金Ti-Nb-Ta-Zr-O合金微观结构和力学性能的影响。结果表明,固溶热处理可使合金晶粒长大。在热旋锻和热处理后的合金中均可观察到α″马氏体相和孪晶存在。热旋锻加工后的合金中α″马氏体相是由加工过程中的应力诱发产生。而固溶热处理后合金中均匀分布的α″马氏体相则形成于热处理过程中。固溶热处理可使合金的塑性提高,伸长率由热处理前的29%增加至热处理后的37%,弹性模量降低,同时强度保持不变。固溶热处理使得合金的"多峰应力振动"现象消失。     

中间热处理温度对DSM11合金组织和性能的影响

研究了不同中间热处理温度对DSM11合金力学性能的影响.实验结果表明中间热处理温度为1120℃时,该合金的拉伸性能和持久性能好于其它热处理制度下合金的性能,从而得出DSM11合金的最佳中间热处理温度为1120℃.     

热处理对Nd-Fe-B系合金磁性能和显微组织的影响

通过对Nd-Fe-B系合金在烧结后的一系列热处理,分析研究了造成热处理后磁性能和显微结构变化的原因。指出烧结后的热处理对不同成分合金的矫顽力会产生不同的影响,某些成分的合金易于通过热处理提高矫顽力,而另一些成分的合金则较为困难。     

热处理工艺对GH4169合金蠕变性能的影响

通过蠕变性能测试和组织观察,研究了不同热处理工艺对GH4169合金蠕变性能的影响。结果表明:经过标准热处理之后,热连轧合金较径锻合金析出的δ相更少,蠕变性能更好。直接时效热处理后的热连轧合金几乎不析出δ相,其蠕变寿命接近于标准热处理径锻合金的两倍。径锻合金蠕变过程产生穿晶断裂,而热连轧合金蠕变过程产生沿晶断裂。     

热处理对W-Ni-Fe合金性能的影响

本报告叙述了热处理对W-Ni-Fe合金性能的影响,烧结态90W-7Ni-3Fe合金的抗张强度和延伸率较低,但经真空热处理后,其强度和延伸率都有很大提高,本试验研究了不同热处理工艺对W-Ni-Fe合金力学性能的影响,比较了合金在热处理前后的显微硬度、氢含量、相成分和断口形貌。实验表明,真空热处理消除了氢的有害影响,增加了基体相的塑性,使合金性能得到明显改善。     

热处理对快淬贮氢合金组织和电化学性能的影响

通过XRD、SEM分析和电化学实验,研究了热处理对快淬贮氢合金组织和电化学性能的影响。研究表明,400℃热处理对快淬合金晶粒变化不明显,900℃热处理后合金晶粒明显长大,1100℃热处理使合金部分熔化,随后发生了平衡凝固;900℃热处理后,单胞体积和放电容量均达到最大值,但充放电循环稳定性最差,400℃和1100℃热处理后,放电容量稍有降低,但充放电循环稳定性较好。     

退火处理对激光熔覆制备FeCrMnCo1.5Ni高熵合金涂层组织的影响

采用激光熔覆技术在Inconel 718合金难体表面制备了FeCrMnCo1.5Ni高熵合金涂层,使用X射线衍射仪、扫描电镜和UMT-3型摩擦磨损试验机研究了退火热处理对合金涂层组织和性能的影响.研究结果表明:经热处理后FeCrVlnCo1.5Ni合金涂层的宏观形貌无明显变化,退火热处理对合金的相结构无影响.合金元素均...     

热处理对热等静压制备的TaW10合金氧含量及力学性能的影响

以氢化-脱氢后的TaW10合金粉末为原料,采用热等静压技术制备了TaW10合金,并对其进行1 800~2 200℃热处理,研究了热处理温度与TaW10合金氧含量及力学性能之间的关系。结果表明,随热处理温度升高,TaW10合金拉伸断裂模式从脆性解理断裂先转变为脆性沿晶断裂,再转变为塑性韧窝断裂。合金强度随热处理温度升高先增大后减小,经2 100℃热处理后达到最大值。当热处理温度升至2 150℃时,热等静压制备的TaW10合金开始表现出塑性变形特征。经2 000℃热处理后,合金氧含量明显降低,此后随热处理温度升高,氧含量变化不明显。热等静压制备的TaW10合金仅在氧含量足够低且经2 150℃以上温度热处理后才具有较好的强度与塑性。     

第三代粉末冶金高温合金René104的研究进展

概述了粉末冶金高温合金的发展历程,并简要介绍了几个典型的第三代粉末冶金高温合金,重点讲述了第三代粉末冶金高温合金:René104的成形工艺、热处理工艺和经不同热处理得到的典型组织,以及René104的单合金双组织热处理工艺.     

热处理温度对Ti-36Nb-2Ta-3Zr-0.3O合金组织和阻尼性能的影响

采用真空自耗熔炼法制备了Ti-36Nb-2Ta-3Zr-0.3O (%,质量分数)合金,通过光学显微镜(OM), X射线衍射仪(XRD)和动态热机械分析仪等测试方法研究了热处理温度对合金的组织和阻尼性能的影响。结果表明:热锻态合金中存在大量的α相,阻尼值较低。在α相转变终了温度以下进行热处理时,合金由β相和α相组成,随着热处理温度升高,α相含量降低,阻尼值升高。在α相转变终了温度以上进行热处理时,α相完全消失,合金仅由β相组成,阻尼值升高。随着热处理温度进一步升高,β晶粒稍有长大,导致合金的阻尼值稍有降低。在不同温度进行热处理的合金均具有较高的阻尼值,其阻尼机制为Snoek型弛豫,与间隙氧原子在体心立方晶格中的基质原子和置换原子附近的重新分布有关。其中,在700℃进行热处理的合金的阻尼值和抗拉强度分别为0.035和670 MPa,是一种具有良好发展前景的高强高阻尼合金。     

工业海洋大气环境下阳极氧化6061铝合金的电偶腐蚀行为

在青岛典型的工业海洋大气环境下,进行硼硫酸阳极氧化6061铝合金与不同表面状态的30CrMnSiNi2A结构钢偶接件的户外大气暴露试验,通过电化学测试、腐蚀产物分析、力学性能检测、断口分析等,研究了偶接件中阳极氧化6061铝合金的腐蚀规律与机理.结果表明:经1 a户外大气暴露试验后,与镀镉钛结构钢偶接的6061阳极氧化铝合金力学性能最优,其强度σ_b和延伸率δ分别比原始试样下降6.45%和4.39%,远优于与结构钢裸材偶接的阳极氧化6061铝合金试样(分别下降10%和62.28%),略优于未偶接试样(分别下降6.77%和10.74%).沿晶腐蚀和表面点蚀是导致阳极氧化6061铝合金力学性能下降的主要原因,最严重的沿晶腐蚀裂纹深度达150 μm.青岛大气中的硫化物不仅会侵蚀试样表面形成硫酸铝,还会浸入到晶界促进沿晶腐蚀.     

Enhancement of strength and superplasticity in a 6061 Al alloy processed by equal-channel-angular-pressing

Pre-equal-channel-angular-pressing (ECAP) solution treatment combined with post-ECAP aging treatment has been found to be effective in enhancing the room-temperature strength of 6061 aluminum alloy. The largest increase in ultimate tensile strength (UTS) (=460 MPa) and yield stress (YS) (=425 MPa) is obtained in post-ECAP aged 6061 Al with six pressings. The strength increases by a factor of 1.4 when compared to T6 treated commercial 6061 Al. The strength of 6061 Al obtained in the present research is higher than that of ECA-pressed 6061 Al with pre-ECAP peak-aging treatment studied by other investigators. The more effective strengthening of post-ECAP low-temperature aging may be linked with the higher dislocation accumulation rate in the solutionized matrix and the presence of higher density particles in the aged matrix. Modest low-temperature (523 K) and high-temperature (813 K) superplasticity is observed in the ECAP 6061 Al, which may be a result of increased grain bundary area from grain refinement.     

Gallium-induced magnesium enrichment on grain boundary and the gallium effect on degradation of tensile properties of aluminum alloys

By applying a controlled amount of gallium (3 mg or 5 mg) to double-notched samples, the effects of the gallium on the grain boundary chemistry and tensile properties of AA6061-T4 alloy were investigated. Commercial-purity aluminum AA1050 was used for comparison to determine whether alloying elements would correlate with Ga-induced embrittlement and to elucidate the physical reason that governed the occurrence of intergranular fracture in the AA6061 Al-Mg-Si alloy. The AA6061 and AA1050 samples wetted by 3 mg or 5 mg of Ga were held statically for 7 days before tensile tests were conducted. The 6061 Al-Mg-Si samples with gallium were fractured intergranularly. However, the Ga-treated AA1050 samples had a mixed fracture mode, showing better strength and ductility than the Ga-treated AA6061 alloy, independent of whether the samples had their longitudinal axis parallel or perpendicular to the rolling direction, or the holding temperatures before tensile tests. Auger electron spectroscopy scanning the intergranular facets on fracture surfaces showed that the Auger peak-to-peak ratio I_Ga/I_Al of 6061 samples was similar to that of 1050 samples, but the high intensity of Mg signal was detected from the intergranular fracture surface of the AA6061 alloy. Magnesium being induced by Ga to enrich on the grain boundary and free surface of the AA6061 alloy was confirmed. The intergranular embrittlement of the 6061 T4 Al-Mg-Si alloy wetted by small amount of Ga involves the combination of the following two effects: Ga metal on grain boundary embrittlement, and Ga-induced magnesium enrichment on grain boundary that further decreases the strength of the grain boundary.     

Recycling of aluminum matric composites

Separation of matrix metals in composites was tried on alumina short fiber-reinforced aluminum and 6061 alloy composites and SiC whisker-reinforced 6061 alloy composite for recycling. It is possible to separate molten matrix metals from fibers in the composites using fluxes that are used for melt treatment to remove inclusions. About 50 vol pct of the matrix metals was separated from the alumina short fiber-reinforced composites. The separation ratio of the matrix from the SiC swisker-reinforced 6061 alloy composite was low and about 20 vol pct. The separation mechanism was discussed thermodynamically using interface free energies. Since the flux/fiber interface energy is smaller than the aluminum/fiber interface energy, the replacement of aluminum with fluxes in composites takes place easily. Gases released by the decomposition of fluxes act an important role in pushing out the molten matrix metal from the composite. The role was confirmed by the great amount cavity formed in the composite after the matrix metal flowed out.     

Mechanical Properties and Microstructural Characteristics of Friction Welded Dissimilar Joints of Aluminium Alloys

Joining of similar and dissimilar combinations of aluminium alloys 2024 and 6061 were performed using friction welding technique. Microstructure, hardness and tensile properties of the joints were characterized. Microstructure of the alloy were found to change significantly across the joint such as fully deformed, partially deformed and undeformed regions due to deformation, frictional heat and alloy characteristics. Extensive fine grain size was observed in the fully deformed region and volume fraction of finer grains was higher in the alloy 2024 as compared to alloy 6061. Hardness was lower in the weld interface region of the similar joints of AA2024 and AA6061. The lower hardness in the dissimilar metal joint was observed in the heat affected zone of alloy 6061. The tensile strengths of the similar joints were 80 and 85% of respective base metal of alloys 2024 and 6061. The strength of the dissimilar metal joint was observed to be similar to the base metal strength of 6061 alloy. Tensile fracture occurred in the region of joints where lower hardness was observed. The maximum elongation were obtained in dissimilar joints of alloys and characterized by scanning electron microscope. It revealed deep dimple patterns unlike what was observed in similar joints.     

Recycling of aluminum matrix composites

Separation of matrix metals in composites was tried on alumina short fiber-reinforced aluminum and 6061 alloy composites and SiC whisker-reinforced 6061 alloy composite for recycling. It is possible to separate molten matrix metals from fibers in the composites using fluxes that are used for melt treatment to remove inclusions. About 50 vol pct of the matrix metals was separated from the alumina short fiber-reinforced composites. The separation ratio of the matrix from the SiC whisker-reinforced 6061 alloy composite was low and about 20 vol pct. The separation mechanism was discussed thermodynamically using interface free energies. Since the flux/fiber interface energy is smaller than the aluminum/fiber interface energy, the replacement of aluminum with fluxes in composites takes place easily. Gases released by the decomposition of fluxes act an important role in pushing out the molten matrix metal from the composite. The role was confirmed by the great amount cavity formed in the composite after the matrix metal flowed out.     

Water Cooling Effects on the Microstructural Evolution and Mechanical Properties of Friction-Stir-Processed Al-6061 Alloy

Water cooling was applied during friction stir processing (FSP) of an Al-6061 alloy, and it was found that the strengthening efficiency induced by water cooling was varied, which was dependent on the initial base metal temper. As to the natural-aged Al-6061 alloy (6061-NA), the stir zone (SZ) was strengthened significantly by water cooling. Compared with the air-cooled FSP sample, the relatively high strength of the water-cooled FSP sample mainly arose from grain refinement, increased density of dislocations and large amounts of fine re-precipitated Guinier–Preston zones in the SZ. On the contrary, as to the annealed Al-6061 alloy (6061-O), the difference in the microstructural evolution between the FSP samples with and without water cooling was nonsignificant, where only finer grain morphology was observed in the water-cooled SZ, and thus the strengthening effects caused by water cooling became less.     

6061铝合金带筋圆管在线淬火模拟分析

通过喷水淬火实验获得6061铝合金的冷却曲线,结合数值计算方法获得材料的在线淬火换热系数,运用ABAQUS有限元软件对带筋圆管在线淬火过程进行了动态模拟。结果表明：在淬火开时阶段,换热系数较小,随着淬火温度降低,换热系数逐渐增大至峰值2kW／m。℃,随后又逐渐减小;在圆管筋部外边缘处冷却最快,型材内表面与筋的连接处冷却最慢;淬火开始2s内型材的整体温差近100℃,随后温差显著减小,型材各部分的温度趋于均匀;淬火初始阶段,管外壁及筋外壁表现为拉应力,管内壁和筋内壁表现为压应力,随着淬火的进行,压应力和拉应力互相转变,最大拉应力和压应力分别为21．7MPa和28．7MPa。     

Simulation of microstructure formation in technical aluminum alloys using the multiphase-field method

Simulation results of microstructure evolution in technical aluminum alloys are presented. The examples comprise solidification and further heat treatment of three different alloy classes, namely for the hypoeutectic alloy AA6061, the near eutectic alloy A356 and the highly alloyed, hypereutectic commercial alloy KS1295 being used in automotive applications. After a short introduction to the simulation models being applied — especially to the multiphase-field approach coupled to thermodynamic databases — the evolving microstructures are discussed in the context of the interplay between thermodynamics, kinetics, interfacial properties and nucleation.     

High-Cycle Fatigue Behavior of Microarc Oxidation Coatings Deposited on a 6061-T6 Al Alloy

The objective of this article is to evaluate the influence of microarc oxidation (MAO) coatings on the high-cycle rotating bending fatigue behavior of the 6061-T6 aluminum alloy. Toward this purpose, the influence of the MAO coating process parameter (current density) and coating thickness on the fatigue life of the 6061-T6 Al alloy has been evaluated in the present study. In addition, the influence of the coating roughness on the fatigue life of the MAO-coated 6061-T6 Al-alloy sample has also been investigated. The results indicate that the high-cycle fatigue life of the 6061-T6 Al alloy is substantially degraded due to the presence of MAO coatings, especially at lower alternating stress values and for thicker coatings. Surface roughness, altered by polishing, does not have any effect on fatigue life. An examination of coated samples interrupted at various fractions of fatigue life leads to the conclusion that the crack propagates from the coating surface to the coating-substrate interface very rapidly and thus fatigue life is largely controlled by the propagation of the crack into the substrate.