烧结工艺对汽车用高硅铝合金组织和性能的影响

研究了不同烧结工艺对汽车用高硅铝合金密度、显微硬度和力学性能的影响。结果表明,当烧结压力一定时,随着烧结温度的增大,硅铝合金的密度先增大后减小,当烧结温度为1 000℃时,合金的密度取得极大值。当烧结压力小于200 MPa且一定时,随着烧结温度的增大,硅铝合金的显微硬度持续上升。当烧结压力为250 MPa时,随着烧结温度的增大,硅铝合金的显微硬度先增大后减小,当温度为1 000℃时,合金致密度具有极大值。当烧结压力一定时,随着烧结温度的升高,硅铝合金的热导率持续增大。当烧结温度一定时,随着烧结压力的增大,硅铝合金的致密度、显微硬度以及热导率均逐渐增大。     

放电等离子烧结制备高铌TiAl合金

以Ti-45Al-8．5Nb-0．2B-0．2W-0．1Y合金粉末为原料,采用放电等离子烧结工艺制备了高铌TiAl合金。结果表明,当烧结温度高于1000℃时,可制备出致密度高、组织均匀的高铌TiAl合金;烧结温度对合金的显微组织影响显著,通过改变烧结温度可得到具有近γ（NG）、双态（DP）、近片层（NL）、全片层（FL）4种典型组织的高铌TiAl合金：合金的室温力学性能与显微组织密切相关,当烧结温度为1100℃时,所制备合金显微组织为细小双态组织,其抗拉强度为1024MPa,延伸率为1．16％,显示出较好的室温力学性能。     

Mn对W-Ni-Fe合金性能的影响

通过液相烧结制备不同Mn含量的90%W-7%Ni-3%Fe合金,研究Mn对合金的烧结温度、保温时间和力学性能的影响。采用SEM观察试样断口形貌;利用金相显微镜观察样品显微组织并检测W晶粒尺寸;并对烧结试样的相对密度、抗拉强度和硬度等性能进行测定与分析。结果表明,当w(Mn)=0.25%时,1425℃保温1h,合金相对密度达到98.3%;1400℃保温45min,合金抗拉强度达到928MPa,硬度HRC达到37.2。W晶粒由20～25μm减少到12～15μm。Mn在相界面上生成的中间相,阻止了W原子在粘接相中的扩散,阻止了W晶粒长大,提高合金的力学性能。     

真空热处理对微波烧结93W-Ni-Fe合金显微组织及力学性能的影响

研究真空热处理对微波烧结挤压棒坯93W-Ni-Fe合金显微组织及力学性能的影响,采用高倍SEM和光学金相分别对合金断口和显微组织进行观察,采用能谱分析仪对合金真空热处理前后各元素含量进行定量分析,并对真空热处理样的相对密度、抗拉强度、延伸率和硬度进行测定和分析.结果表明:经真空热处理后,钨合金的各项力学性能都得到了提高,抗拉强度和延伸率提高显著,抗拉强度从920 MPa提高到了988 MPa,延伸率从9.7％提高到了18.6％;真空热处理后,显微组织中钨晶粒的连接度降低,合金断口中钨晶粒的穿晶解理断裂和粘结相的延性撕裂增多;真空热处理后合金粘结相中的钨含量明显降低.     

Fe含量和烧结温度对Al-4Cu-xFe合金组织及性能的影响

采用粉末冶金法制备了Al-4Cu-xFe(x=0、1.5、2.5、3.5、4.5)合金,利用光学显微镜、扫描电子显微镜、显微硬度计和万能试验机等研究了不同Fe含量和烧结温度对合金组织及性能的影响。研究结果表明,随着Fe含量和烧结温度的提高,合金的致密度、硬度、抗拉强度和伸长率呈现先增大后减小的趋势;当Fe含量为1.5%,烧结温度为570℃,烧结时间为40 min时,可获得组织和力学性能良好的Al-Cu-Fe合金。     

再生高密度钨合金的性能

采用氧化-还原法回收钨合金切削废料,用回收粉末及镍、铁元素粉配制成91W-6Ni-3Fe系高密度合金的混合粉,经压制、脱胶、烧结制得再生高密度钨合金.结果表明:所得再生合金的性能同非回收粉末所制备的合金性能相当,再生钨合金的密度随着烧结温度的升高而先升高后有所降低,最大密度为17.12 g/cm3,硬度随着烧结温度的升高而降低;当烧结温度为1 440℃时再生合金的强度和塑性达到较好的配合,抗拉强度为922.95MPa,延伸率为20.18%;经真空热处理后,再生钨合金性能得到改善,抗拉强度和延伸率得到不同程度的提高,抗拉强度比热处理前提高了约6.44%,延伸率比热处理前提高了约43.42%.     

固溶处理温度对7075铝合金组织和性能的影响

研究了不同固溶处理温度对7075铝合金组织、显微硬度和力学性能的影响。结果表明,随着固溶温度的升高,合金组织中未溶相先减少后增多,铝合金的显微硬度、抗拉强度和屈服强度先增大后减小。当固溶温度为460℃时,合金中未溶相数目最少,合金硬度值最大(194.1 HV),抗拉强度和屈服强度达到最大值(709和653 MPa)。当固溶处理温度升高时,合金试样的伸长率先减小后增大;当固溶温度为470℃时,伸长率有最小值(4.9%)。     

时效制度对2A97铝-锂合金组织和性能的影响

通过拉伸测试和透射电镜分析,研究时效温度和时间对2A97铝锂合金组织和性能的影响。结果表明:经淬火后分别在135℃和155℃时效,随着时效温度升高,2A97合金强度升高,达到峰值强度的时间提前,延伸率降低;随着时效时间延长,合金屈服强度升高,抗拉强度则先升高而后降低,出现峰值强度,延伸率下降;当合金在155℃时效36 h,获得最佳强度和塑性匹配,抗拉强度为500 MPa,屈服强度为413 MPa,延伸率为7%;随着时效温度升高,合金组织中T1(Al2CuLi)相数量增加;135℃的过时效合金显微组织主要为θ′/θ″(Al2Cu)相和δ′(Al3Li)相,155℃的时效合金显微组织主要为T1相、θ′/θ″相和δ′相。     

INCO-617合金空心球颗粒的制备与力学性能研究

在1100-1230℃的温度下真空烧结表面涂覆一层由聚乙烯醇粘结剂、合金粉末和分散剂构成的浆料的聚苯乙烯球制得高孔隙率的INCO-617合金空心球颗粒,对不同烧结工艺下制备的空心球颗粒的显微组织和力学性能进行了研究.结果表明,INCO-617合金空心球颗粒的密度随烧结温度的升高和烧结时间的延长而增加,其密度值在1.504～2.113 g/cm3之间.烧结温度的升高和烧结时间的延长可以明显减少球壁的残余孔隙,这是空心球颗粒显微硬度和压缩性能提高的主要原因,并且,随着球壁内残余孔隙的降低,空心球颗粒压缩时脆性破坏的倾向被抑制.     

旋锻Mo-Ti-Zr合金棒材的退火行为

采用冷等静压、高温烧结和直接高温旋锻的方法制备Mo-Ti-Zr合金棒材,研究不同退火温度对合金力学性能与显微组织的影响以及对断面收缩率为30%的旋锻Mo-Ti-Zr合金棒材的退火行为。结果表明:当退火温度低于1000℃时,随着退火温度的升高,Mo-Ti-Zr合金硬度未急剧下降,抗拉强度和伸长率逐渐提高;经900℃退火后,合金抗拉强度达到669MPa,伸长率达到3.1%,获得良好的综合力学性能;当退火温度在800～1000℃范围内时,Mo-Ti-Zr合金晶粒发生再结晶细化;旋锻态Mo-Ti-Zr合金的断口主要为穿晶解理断裂,随着退火温度的提高,出现较多细晶粒的穿晶断裂和沿晶断裂。     

Transient Liquid-Phase Sintering Characteristic of W-Ni-Fe Alloy via Microwave-Assisted Heating

研究了W-Ni-Fe合金在2.45 GHz微波炉中瞬时液相烧结的致密化行为和力学性能。结果表明:微波辅助热场下的93W-Ni-Fe合金显示出优异的力学性能和快速的致密化过程,其压缩试样在1500℃下烧结5 min后,拉伸强度、延伸率、相对密度和硬度(HRC)分别是1200 MPa,16.6%,98.6%和42.0;在微波辅助热场下,试样烧结可以减少80%的烧结时间;微波辅助热场下的瞬时液相烧结有利于减少烧结时间,加快致密化过程,并且有利于钨晶粒的细化,获得组织均匀和综合性能高的W-Ni-Fe合金。     

Characterizations and mechanical properties of impregnated diamond segment using Cu-Fe-Co metal matrix

Diamond impregnated Cu-Fe-Co based saw-blade segments are directly processed by vacuum and pressure-assisted sintering at different temperature,with the purpose of reducing the cobalt content in diamond tools.Copper and iron are used as the bonding elements and cobalt-chrome pre-alloyed powder is used as the hardening phase.Effects of sintering temperature on microstructures and mechanical properties of the sintered matrix and diamond graphitization were investigated by X-ray diffraction analysis,electron probe micro-analyzer,universal testing machine,digital Rockwell hardness tester and Raman scattering analyzer.Results showed that microstructures of the sintered matrix were refined and porosities in the sintered matrix were closed to a more spherical-like shape with the increase of the sintering temperature.Densification,hardness and tensile strength of the matrix sintered at 820 ℃ were 12.75％,2.72％ and 156.38％ higher than that of the matrix sintered at 740 ℃,respectively.Diamond graphitization was not occurred at 820 ℃.The hardness and the tensile strength rose 32.8％ and 13.5％,respectively,after 7.5 h ageing treatment.The matrix densification ascent and the dispersed distribution of Co-Cr pre-alloyed powders contributed a hardness improvement and a tensile strength improvement to the Cu-Fe based matrix.     

Deoxidation and subsequent densification of sintered titanium by Ca deoxidizer

In this study, a sintering process involving simultaneous deoxidation and sintering was developed, using the vapor of a deoxidizer (Ca) to produce low-oxygen, high-density titanium. Compared to a series of reference titanium powder samples, the bodies sintered with Ca exposure had an ～1,400 ppm lower oxygen content, resulting in an ～2% increase in their density. This appears to be the result of decreased surface oxidation on the titanium, as increased oxidation suppresses densification at high sintering temperatures. The effect of the Ca deoxidizer was a lower oxidation, thereby increasing the sintered density. The Vickers hardness of sintered bodies from both experiments increased from an initial value of ～249 Hv at 900 °C to ～286 Hv at 1,400 °C, respectively. Moreover, both experiments revealed a tensile strength of ～170 MPa at 900 °C that finally increased to ～218 MPa at 1,400 °C. Meanwhile, the bodies sintered with Ca, the elongation was on average over 1% higher than contrary samples.     

高体积含量TiC/Fe复合材料的制备及力学性能

以TiC粉、还原铁粉和羰基铁粉为原料,采用行星球磨混料、冷压成型后无压烧结工艺制备了TiC颗粒体积含量为70%~90%的TiC/Fe复合材料,重点研究了羰基铁粉添加量、烧结温度及TiC体积含量对TiC/Fe复合材料的微观结构和力学性能的影响。结果表明:羰基铁粉的最佳添加量为铁基体粉体积含量的60%。当TiC体积含量一定时,随烧结温度的升高,TiC/Fe复合材料的相对密度、维氏硬度与弯曲强度均先增大后减小,经1500℃烧结后,复合材料的综合性能最佳。其中,70%TiC/Fe的相对密度及弯曲强度最高,分别为99.5%和437MPa;80%TiC/Fe的维氏硬度最大,为12.2GPa。     

Pressureless sintering of nanocrystalline hydroxyapatite at different temperatures

In this work, the sintering behaviour of hydroxyapatite (HA) at different temperatures was studied. Nano HA powders synthesized by sol-gel technique were uniaxially pressed at 30 MPa into pellets and cold isostatically pressed at 200 MPa. The pellets were sintered in air at temperatures ranging from 900 °C to 1400 °C with a holding time of 2 h. It was observed that, at a sintering temperature of 1200 °C when the material was composed of pure HA phase, the samples exhibited densities of > 98.5 % of the theoretical value and possessed a hardness value of 5.89 GPa. Decomposition of HA into the secondary phases of TCP and CaO was found to occur at 1300 °C and 1400 °C, respectively. Changes in the microstructure, relative density and hardness of the sintered HA ceramics with the sintering temperature were also analyzed. The variation in the hardness was found to be dependent on the relative density up to a threshold grain size limit of 2 μm. However, beyond this threshold, no correlation existed between the two properties. Porosity and grain size were found to play an important role in determining the properties of the sintered HA compacts.     

熔体温度对AZ31B镁合金铸态组织及力学性能的影响(英文)

采用自制的电阻炉研究熔体温度对AZ31B镁合金凝固组织与拉伸性能的影响。结果表明:在温度低于850℃水冷时,金属型AZ31B镁合金铸锭等轴枝晶的尺寸随着熔体温度的升高呈直线下降,超过850℃后变化不大。组织中第二相呈现出先细化后粗化的变化规律。AZ31B镁合金试样的抗拉强度、伸长率和屈服强度随着熔体温度的提高而先快速增大后略有减小,熔体温度为850℃时试样的抗拉强度达到260MPa,屈服强度达到75.4MPa,伸长率达到27.57%,比熔体温度为750℃时的分别提高了15%、13%和61%。DSC分析表明,升高熔体温度使凝固开始点温度降低,临界晶核半径减小,从而增加了熔体中的过冷度,提高了熔体中非均匀形核率,是镁合金晶粒细化和拉伸性能提高的主要原因。     

Sintering Behavior of Elemental Powders with FeB Addition in the Composition of Martensitic Stainless steel

The effect of sintering additive for the development of high-strength martensitic stainless steel from elemental powders was studied. The sintering parameters investigated were: sintering temperature, sintering time, and wt.% of FeB. In vacuum sintering, effective sintering took place between 1300 and 1350 °C with 1-1.5 wt.% FeB addition. The maximum sintered density and ultimate tensile strength (UTS) were achieved after sintering at 1350°C for 60 min with 1 wt.% FeB. Secondary pores were observed in samples containing more than 1.5 wt.% FeB sintered at 1350 °C for 60 min. More than 1.5 wt.% FeB content and temperature above 1350°C caused slumping of the specimens. Maximum UTS of 505 MPa was achieved with 1 wt.% FeB content. Above 0.5 wt.% FeB content, maximum increase in density was observed. Fracture morphologies of the sintered samples are reported.     

Effect of heat treatment on microstructure and properties of semi-solid squeeze casting AZ91D

Semi-solid AZ91D magnesium alloy billets were prepared by near-liquidus heat holding. Semi-solid squeeze casting was conducted at 575, 585 and 595 ℃, respectively, with 1 mm·s~(-1) squeeze speed. The semisolid squeeze casting AZ91D samples were heat treated by T4(solution at 415 ℃ for 24 h) and T6(solution at 415 ℃ for 24 h + 220 ℃ for 8 h) processes, respectively. The microstructure and mechanical properties of the alloy in different states were investigated by means of OM, SEM and tensile testing machine. The results show that compared to as-cast alloy, the grain size of the semi-solid squeezed AZ91D decreased significantly, and with the increase of semi-solid squeeze temperature, the grain size of AZ91D increased. The grains of the alloy were refined by T4 treatment, and further refined by T6 treatment. T6 treatment greatly improved the tensile strength, elongation, and hardness, but did not significantly improve yield strength. After 575 ℃ squeeze casting and T6 treatment, the ultimate tensile strength(UTS) reached 285 MPa, the elongation reached 13.36%, and the hardness also reached the maximum(106.8 HV), but the yield strength(YS) was only 180 MPa. During the process of semi-solid squeeze casting and heat treatment, the matrix grain was refined and a large number of precipitated and secondary precipitated phases of Mg_(17)Al_(12) appeared. Both the average size of matrix grain and secondary precipitated phase decreased, while the volume fraction of secondary precipitated phase increased. All these resulted in high tensile strength, elongation and hardness.     

烧结温度对振荡压力烧结工艺制备高性能氧化锆陶瓷的影响

采用新型振荡压力烧结技术制备了高性能氧化锆陶瓷,并系统研究了该工艺中烧结温度对于氧化锆陶瓷中致密度、晶粒尺寸、微观结构以及力学性能的影响。结果表明:在振荡压力烧结工艺下,随着烧结温度的提高,氧化锆试样致密度变化不明显,但晶粒尺寸不断增加,试样表面均几乎无气孔。当目标温度达到1300℃时,氧化锆陶瓷的硬度和抗弯强度均最大,分别为16.6 GPa和1455 MPa。相比常压和热压烧结工艺,振荡压力的引入明显降低了氧化锆陶瓷的致密化温度,且获得了更高的力学强度和断裂可靠性。     

Inconel718合金金属注射成形制备过程及力学性能

以Inconel718气雾化预合金粉末为原料,采用金属注射成形(MIM)工艺制备Inconel718合金材料.研究Inconel718合金烧结、热等静压(HIP)、热处理对合金显微组织、密度和力学性能的影响.结果表明:经1275 ℃烧结后,烧结体的相对密度达到98%.烧结体经HIP处理后,达到全致密.经烧结+HIP+热处理后,组织弥散析出了大量的γ″相和γ′相,其室温抗拉强度为1250 MPa,延伸率为21.7%;650 ℃抗拉强度为1177 MPa,延伸率为16.6%,其达到或超过了同牌号锻造合金的性能.