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 powder metallurgy of Cu

A series of experiments were carried out using different admixed lubricant contents, different compaction pressures and temperatures in order to study the warm compaction of copper powder. Results show that too much admixed lubricant will lead to the squeeze out of the lubricant from the compact during the warm compaction processing of Cu powder. Results also show that blisters can be found in sintered samples that contain lubricant less than 0.15%(mass fraction). Optimal warm compaction parameters for producing high density powder metallurgy copper material are obtained. Compacts with green density of 8.6 g/cm^3 and a sintered density of 8.83 g/cm3 can be produced by warm compacting the Cu powder, which contains 0.2% admixed lubricant, and is compacted at 145℃ with a pressure of 700 MPa.     

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.     

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     

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。     

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

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ (ＭＭＣｓ)ｃｏｍｂｉｎｅｓｔｈｅａｄｖａｎｔａｇｅｓｏｆｄｉｆｆｅｒｅｎｔｍａｔｅｒｉａｌｓ.Ｉｔｉｓａｈｏｔｓｐｏｔｉｎｔｈｅｐａｓｔｄｅｃａｄｅｓ .Ｐｏｗｄｅｒｍｅｔａｌｌｕｒｇｙ (     

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。     

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。     

Effect of sintering parameters on warm compacted iron-based material

1　INTRODUCTIONItiswellknownthatincreasingdensityisthebestwaytoincreasetheperformanceofpowdermet allurgy(P/M ) parts.ConventionalP/Mprocessingcanproduceiron basedpartswithdensitylessthan 7.1g/cm3(arelativedensityof 90 %approximately) .Theirmechanicalpropertiesaresubstantiallylessthanthoseoftheirfulldensitycounterpart .TherearemanymethodsthatcanproduceP/M partswithrela tivelyhighdensitysuchaswarmcompaction ,hightemperaturesintering ,doublepress/doublesinteringandforging .Warmcompactioni…     

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.     

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.     

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.     

自蔓延高温合成TiC复合添加剂增强铁基粉末冶金材料

采用以自蔓延高温合成技术制备的TiC/Fe(Mo）复合粉末为添加剂增强铁基粉末冶金材料,探讨复合增强粉末中金属相的种类、含量对增强体结构及烧结复合材料性能的影响。结果表明,含Fe,Mo为10％－20％的TiC/Fe(Mo）复合粉末具有较高的增强效果;在复合粉末的自蔓延高温合成中,加入金属Mo,有利于TiC与金属相的润湿,从而提高增强效果。     

Warm die compaction and sintering of titanium and titanium alloy powders

A study has been made of the effect of non-lubricated warm die (200 °C) compaction on the densification of hydride–dehydride (HDH) Ti powder, pre-alloyed (PA) Ti-6Al-4V and Ti-10V-2Fe-3Al powders, and HDH Ti and V-Fe-Al master alloy powder blends, compared to cold die compaction. Depending on the compaction pressure, which was varied from 200 to 1000 MPa, non-lubricated warm die (200 °C) compaction was very effective for −100 mesh HDH Ti powder, increasing the green density by 5.0–9.4% theoretical density (TD). Die wall lubrication with stearic acid showed no influence on the green density when compacted at 800 MPa. With warm die (200 °C) compaction, achieving a green density of greater than 90%TD was straightforward for HDH Ti powder when compacted at ≥750 MPa. Accordingly, near pore-free (≥99.5%TD) Ti microstructures were obtained after sintering at 1300 °C for 120 min in vacuum when compacted at 1000 MPa. The resulting increment in the sintered density was between 2.0%TD and 4.4%TD. Warm die (200 °C) compaction showed no effect on PA Ti-10V-2Fe-3Al powder and only a small effect on PA Ti-6Al-4V powder when compacted at 1000 MPa. However, it was still virtually effective for Ti-10V-2Fe-3Al powder blends made of HDH Ti powder and V-Fe-Al master alloy powder. The observations were compared with literature data and discussed in accordance with the yield strength of Ti, Ti-6Al-4V, Ti-10V-2Fe-3Al and Al₃V as a function of temperature.     

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…     

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。     

压扭工艺改善钼粉末温压成形的模拟分析

运用MSC．Marc有限元仿真软件,采用基于更新拉格朗日方法的热-机耦合分析方法,模拟了钼粉温压和温压扭成形过程,获得了2种工艺条件下的粉坯相对密度分布规律,验证了有限元模型的可靠性。结果表明：压扭工艺可以减小粉坯端面边缘处相对密度分布梯度,增大侧壁附近粉末变形量,并显著提高平均相对密度及相对密度分布的均匀性。     

预混合工艺对铁基粉末冶金材料组织和烧结性能的影响

通过加入新型润滑剂制得Fe-2Cu-0.8C预混合铁基粉末,并制备了同成分机械混合粉末进行对比试验。对粉末流动性、松装密度以及压制性能进行了测试,并对烧结体的微观组织进行表征。结果表明:制备的预混合粉末流动性和松装密度均优于机械混合粉。当润滑剂加入量为0.6 mass%时,经600 MPa压力下压制所得的生坯密度为7.01 g/cm^3,烧结体密度为7.11 g/cm^3,批量压制时零件质量变化小于0.15%。通过预混合工艺,使得铜和石墨颗粒粘结到铁颗粒表面上,从而达到防止偏析和提高批次稳定性的目的。使用预混合粉末不仅提高了烧结体的尺寸精度和性能,同时可制备出更光洁的零件表面,进行形状复杂零件生产时更能体现出其在稳定性方面的优势。