Effects of lubricant''''s friction coefficient on warm compaction powder metallurgy

1　INTRODUCTIONWarm compaction is a relatively simple and e conomical process that can produce sintered partswith density up to 94% of the theoretical pore freedensity[1 3], and its potential is tremendous. Withminor modification on the conventional powdermetallurgy equipment and approximately 20%higher cost than conventional cold compaction,green compact density of 7.5 g/cm3 can be obtainedby single press. The only difference between thewarm compaction and th…     

Warm compaction of Al2O3 particulate reinforced powder metallurgy iron-base composite

1　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｆｅｒｅｎｃｅｓｆｏｃｕｓｅｄｏｎｗａｒｍｃｏｍｐａｃｔｉｏｎｗｅｒｅｆｉｒｓｔｐｕｂｌｉｓｈｅｄｉｎ 1994 [1,2 ] .Ｉｔｉｓａｒｅｌａｔｉｖｅｌｙｓｉｍｐｌｅａｎｄｅｃｏｎｏｍｉｃａｌｐｒｏｃｅｓｓｔｈａｔｃａｎｐｒｏｄｕｃ     

Die wall lubricated warm compaction of iron-based powder metallurgy material

Lubricant is harmful to the mechanical properties of the sintered materials,Die wall lubrication was applied on warm compaction powder metallurgy in the hope of reducing the concentration level of the admixed lubricant.Iron-based samples were prepared by die wall lubricated warm compaction at 175℃,using a compacting pressure of 550MPa.Emulsified polytetrafluoroethylene(PTFE) was used as die wall lubricant.Admixed lubricant concentration ranging from 0 to 0.5% was tested.Extremely low admixed lubricant contents were used.Results show that in addition to the decrease in ejection forces,the green density of the compacts increases with the decrease of admixed lubricant content until it reaches the maximum at 0.06% of lubrcant content,then decreases with the decrease of admixed lubricant content.The mechanical properties of the sintered compacts that contain more than 0.06% admixed lubricant are better than those of the samples that contain lesser lubricant.No scoring was observed in all die wall lubricated experiments.     

Warm compaction behaviors of iron-based powder lubricated by different kinds of graphite

1　INTRODUCTIONConventionalpowdermetallurgy(PM ) process ingcanproduceiron basedPM partswithadensitylessthan 7.1g/cm3(arelativedensityofapproxi mately 90 % ) .Theirmechanicalpropertiesaresub stantiallylessthanthoseoftheirfulldensitycounter part.IncreasingdensityisthebestwaytoincreasetheperformanceofthePM parts .Therearemanyprocessesthatcanproduceiron basedPM partswithhighdensitysuchaspowderforging ,doublepress/doublesinter(DP/DS)andCuinfiltration ,butwarmcompactionisthemosteconomical…     

粉末冶金温压成形技术的研究现状

粉末冶金温压成形,在得到较高致密度零件的同时,可以较铸造和锻造显著的降低原料成本,缩短零件的研制周期,具有重要的研究价值。本文概述了国内外温压成形技术的应用、发展现状及温压成形工艺的关键技术,指出了粉末冶金温压成形技术的发展方向。     

Numerical simulation in powder compaction of metallurgy component

1Introduction Forming multi-level component in die compaction,the density is more or less inhomogeneous depending onthe part geometry,the tool design and the frictionbetween powder and die wall[1?3].The productdistortions are result of inhomogeneous densi…     

钛合金粉末温压成形行为

研究了钛合金粉末的温压成形行为。结果发现，在同一压制压力下，钛合金粉末的生坯密度均在140℃左右达到最大值，高于或低于这一温度，生坯密度反而降低。在压制压力为500MPa下，温压成形的脱模力比室温成形的脱模力降低27．7％。同时，温压成形较室温成形改善了钛合金件的显微组织。     

二次温压对铜粉和镍粉反应的影响

研究了铜和镍混合粉经冷压和一次冷压、二次温压两种压制方法成型后的烧结体的显微组织以及密度和硬度。结果发现，在铜粉和镍粉反应过程中，二次温压对烧结体显微组织、密度和硬度有重要的影响。二次温压较冷压有利于Cu-Ni单相固溶体的形成，可以提高铜粉和镍粉烧结体的密度和硬度。     

Warm compacted NbC particulate reinforced iron-base composite(Ⅰ)--Effect of fabrication parameters

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ (ＭＭＣｓ)ｃｏｍｂｉｎｅｓｔｈｅａｄｖａｎｔａｇｅｓｏｆｄｉｆｆｅｒｅｎｔｍａｔｅｒｉａｌｓ.Ｉｔｉｓａｈｏｔｓｐｏｔｉｎｔｈｅｐａｓｔｄｅｃａｄｅｓ .Ｐｏｗｄｅｒｍｅｔａｌｌｕｒｇｙ (     

润滑剂含量不同时W-Ni-Fe合金的温压行为

研究90W-7Ni-3Fe合金的温压成形工艺,探讨润滑剂含量不同时温压行为对硬粉的作用,并比较温压工艺与常温压制工艺的不同。结果表明：在相同单位压制压力下,温压压坯密度明显高于常温压制的;润滑剂含量为0.6%（质量分数）时压坯密度达到最大值,温压压制与常压压制相比,压坯密度增加0.26 g/cm3;润滑剂含量超过0.6%后,压坯密度又逐渐下降;添加润滑剂后合金的脱模力明显降低,其温压脱模力较常压脱模力小;试样的抗拉强度、伸长率在润滑剂含量为0.6%时达最大值,这与烧结体的密度随润滑剂含量的变化一致;同时温压烧结坯的密度与常压试样的区别不明显,但抗拉强度和伸长率都高于同批的常压试样。     

Sinter-hardening properties of partially-diffuse alloyed Fe-Cu-Ni-Mo-C material prepared by die wall lubricated warm compaction

The sinter-hardening properties of a partially-diffuse alloyed Fe-2Cu-2Ni- 1Mo- 1C material were investigated. Samples were formed by die wall lubricated warm compaction method, then, sintered in hydrogen atmosphere at 1 150 ℃ for 1 h and cooled at 4.6, 2.9 and 1.5 ℃/s, respectively, from 900 ℃ down to 600℃. Effects of cooling rate on mechanical properties and microstructure of the material were discussed. The results show that when the cooling rate increases, the tensile strength of the material increases, while, the elongation shows opposite result. The sintered material has a tensile strength of 872 MPa and an apparent hardness of HB 257 at a cooling rate of 4.6 ℃/s. Slight shrinkage is observed. Heterogeneous microstructures containing martensite, bainite, pearlite and nickel-rich retained austenite are observed in the material. Higher martensite content can be obtained at higher cooling rate, while, at lower cooling rate, pearlite and retained austenite dominated the microstructure.     

Worn surface characteristics of Cu-based powder metallurgy bake materials for aircraft

Cu-based powder metallurgy brake materials are used for aircraft widely and successfully.The characteristics of worn surface of Cu-based powder metallurgy brake materials for aircraft after working under service condition were studied,and two main wear mechanisms were discussed.The results show that the main components of worn surface are graphite,SiO2,Fe,Cu and oxide of Fe(Fe3O4 and FeO);the worn surface can be divided into three zones:severe wear zone,mild wear zone,and low wear zone; fatigue wear and grain wear are the main wear mechanisms of Cu-based materials.Some debris kept between brake discs reduce the wear rate to a certain extent by taking part in the regeneration of friction film.     

Effects of temperature on the mechanical properties of Ti6Al4V powder compacts prepared by magnetic pulse compaction

The effects of temperature (0-500°C) on the compressive strength,hardness,average relative density,and microstructure of Ti6Al4V powder green compacts prepared by magnetic pulse compaction were investigated.The results show that with increasing heating temperature,the compressive strength first increases and then decreases with the maximum value of 976.74 MPa at 400°C.The average relative density and hardness constantly increase,and their values reach 96.11% and HRA 69.8 at 500°C,respectively.The increase o...     

Effects of temperature on the mechanical properties of Ti6Al4V powder compacts prepared by magnetic pulse compaction

The effects of temperature (0–500°C) on the compressive strength, hardness, average relative density, and microstructure of Ti6Al4V powder green compacts prepared by magnetic pulse compaction were investigated. The results show that with increasing heating temperature, the compressive strength first increases and then decreases with the maximum value of 976.74 MPa at 400°C. The average relative density and hardness constantly increase, and their values reach 96.11% and HRA 69.8 at 500°C, respectively. The increase of partial welding is found among the junctions of particles inside the compacts; there is no obvious grain growth inside the compacts within the temperature range.     

Microstructure and mechanical properties of Ti6Al4V powder compacts prepared by magnetic pulse compaction

Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.     

铜对粉末冶金航空刹车材料物理力学性能的影响

研究了大范围铜含量对粉末冶金航空刹车材料物理力学性能的影响。结果表明 :铜通过对铁基组织的合金化和沉淀强化 ,影响刹车材料的密度、孔隙度、基体显微硬度、表观硬度以及抗压强度。Cu的含量为 30 %时航空刹车材料综合性能最佳。     

装粉方式对钛粉压制成形影响的数值模拟

用MSC.Marc软件模拟了3种不同装粉方式下钛粉压制成形过程中粉末的流动情况及压坯的密度分布规律.结果表明:粉末装粉方式对粉末压制过程及压坯密度有较大的影响,与平式装粉方式相比,采用凸式装粉,试样的烧结坯密度提高了6%,孔隙分布的均匀性也得到相应的改善.     

一种镍基粉末高温合金的静态再结晶行为

用EBSD和SEM等技术手段研究了热变形后的某种新型镍基粉末高温合金在不同温度下的静态再结晶行为。结果表明,镍基高温合金的静态再结晶开始温度在900℃以上,合金的显微硬度显著下降;而在组织中存在的γ’相和碳化物颗粒抑制再结晶晶粒的长大,在1100℃再结晶退火后合金的平均晶粒尺寸在约5μm。     

预合金粉对粉末冶金NiFe18.5Al25合金性能的影响

将元素Ni、Fe和Al粉以摩尔比56.5-18.5-25配料,分别按元素粉末高能球磨(300 r/min, 12 h)、元素粉末直接干混、50%元素粉+50%预合金粉末干混3种方式混料;混料在500 MPa的压力下压制成形,1 280 ℃下烧结;对合金烧结态进行相对密度测定、力学性能检测、X射线衍射分析(XRD)和断口形貌观察.结果表明:50%元素粉+50%预合金粉制备的合金性能最好,密度可达到6.61 g/cm3(相对密度94.8%),烧结态抗拉强度可达到868 MPa,说明元素粉末中添加的预合金粉可以控制烧结过程,提高合金的烧结密度,同时增强合金的力学性能.     

粉末冶金TiAl合金排气门的研制

利用元素粉末冶金方法制备了TiAl合金排气阀。为提高排气门杆部的致密度、均匀度 ,设计了特有的径向热压工艺 ,并从理论上分析了与该工艺相关的压坯密度、致密化和应力变化规律。制备出高径比为 10 .7,密度为 3.79g/cm3 的粉末冶金TiAl合金汽车发动机排气门