Fe—P—C—Cu合金的成分、组织与性能

在铁基粉末合金中,采取铁磷合金化,是改善和提高铁基粉末冶金制品的强度和韧性的有效方法之一。在Fe-P-C三元系合金的基础上添加一定量的铜元素,不仅可以减少合金的烧结收缩,而且能够进一步提高合金的机械性能。
本文着重讨论了Fe-P-C-Cu合金的成分、组织与性能之间的关系,研究了不同的铜含量、碳含量和烧结温度对合金的组织、机械性能及烧结收缩的影响规律。     

稀土硅铁合金对提高铁基烧结材料材质性能的研究

本文介绍加入稀土硅铁合金对铁基烧结材料性能的影响和稀土中间合金作为合金添加剂引入到铁基粉末冶金材料中的可能性;研究了合金加入量及相应的工艺参数。试验结果表明,加入一号稀土硅铁合金2～3%,在烧结温度1150～1200℃,保温时间1.5～2小时,压坯初始密度大于6.5克/厘米~3的条件下,制得的烧结材料综合机械性能达到下述指标:抗拉强度σ_b>50公斤力/毫米~2,硬度 HRB>80,冲击韧性ak=1.8～2.3公斤力·米/厘米~2。制品尺寸收缩稳定,组织主要呈珠光体,晶粒细小均匀,孔隙呈球状。     

放电等离子烧结制备储氢合金的应用研究现状

介绍了放电等离子烧结制备储氢合金的可行性,从La-Mg-Ni系、Mg基、Ti-V基合金的微观结构及其吸放氢性能等角度综述了放电等离子烧结在储氢合金中的应用研究进展,并指出储氢合金吸放氢性能的改善原因在于适当温度的放电等离子烧结促进了合金中新相的形成,控制了合金晶粒尺寸。     

Fe-Cu-Pb-C系含油轴承的研制

研究了Fe-Cu-Pb-C系合金烧结温度范围和铜的加入量对合金性能的影响。铅是固体润滑剂,可提高Fe-C系合金的减摩性能,虽然铅的加入使合金的强度有所下降,但通过加入铜能有效地抑制强度的降低。     

烧结温度对WC－TiC－Co两相合金的影响

对不同温度烧结的ＷＣ－ＴｉＣ－Ｃｏ两相合金的组织结构进行了全面的观察和分析，并对不同温度烧结的刀片进行了切削试验。结果表明：由饱和的ＴｉＣ－ＷＣ（质量比为３０：７０）固溶体与Ｃｏ粉制成的两相合金，在各种烧结温度下都会出现游离的ＷＣ相，且其相对量随着烧结温度的升高而减少；合金中碳化物的晶粒尺寸随着烧结温度的升高而增大；当烧结温度为１４８０℃时，合金的切削寿命具有最大值。     

烧结青铜—铁轴承材料的研制

烧结青铜(6-6-3)-铁轴承材料具有比烧结青铜(6-6-3)更好的机械性能和摩擦磨损性能。铁元素的加入,使烧结尺寸变化(负值)降低,形成了具有均匀金相组织的铜-铁假合金。研究了铁含量和烧结温度对试样烧结尺寸交化、力学性能和摩擦磨损性能的影响,分析了影响机理。     

Fe－Cu－Pb－C系含油轴承的研制

研究了Ｆｅ－Ｃｕ－Ｐｂ－Ｃ系合金烧结温度范围和铜的加入量对合金性能的影响。铅是固体润滑剂，可提高Ｆｅ－Ｃ系合金的减摩性能，虽然铅的加入使合金的强度有所下降，但通过加入铜能有效地抑制强度的降低。     

烧结气氛与温度对AlCuMgSi合金性能的影响

采用Al-3.8Cu-1.0Mg-0.75Si铝合金粉末,分别在高纯氮气、高纯氩气、高纯氢气和分解氨等4种气氛下烧结,对比研究不同烧结气氛下制备的合金致密度、力学性能、尺寸变化和显微组织等性能。同时研究高纯氮气气氛下烧结温度对合金性能的影响。结果表明,在590℃烧结温度条件下,高纯氮气气氛中烧结的合金性能最佳,密度达2.66 g/cm3、致密度为97.1%,硬度为23 HRB,抗拉强度为205 MPa,尺寸收缩率为1.65%;高纯氢气中烧结的合金密度、硬度及强度都最低,抗拉强度为96 MPa,屈服强度只有74 MPa,合金组织中存在大量孔隙。随烧结温度升高,烧结坯中的液相逐渐增多,使合金烧结密度增大,强度提高,在590℃烧结的合金抗拉强度最高,为205 MPa;610℃烧结时产生过烧现象,元素偏析严重,合金性能下降。     

W-Ni-Cu高比重合金注射成形烧结收缩及性能的研究

研究了W-Ni-Cu高比重合金注射成形工艺过程收缩率和性能。比较了模具尺寸、注射坯尺寸、烧结坯尺寸，及烧结阶段各方向收缩率的关系，发现实际收缩与理论预测收缩率较为一致，但在厚度方向存在与其他方向收缩不一致的情形，这与由重力作用产生的塑料流动有关；还探讨了烧结坯密度与烧结条件的关系，测定了烧结坯的力学性能及断口形貌、金相组织，烧结坯在1400℃，90min烧结达到了99％的相对密度，断裂强度600MPa以上。     

Fe-P-C-Cu-Mo系粉末合金的组织、性能及断口

研究了Fe-P-C-Cu-Mo系铁基粉末冶金材料中合金元素、烧结温度对合金组织及性能的影响,以及不同回火温度下磷的分布及其对合金断裂方式的影响。
通过研究得出:Fe-0.60%P-0-44%C-1.0%Cu-0.50%Mo合金在1160-1240℃烧结,保温1-2小时,可以获得较好的性能;若进一步经过850-900℃淬火,200℃或600℃回火,则合金的综合机械性能可以显著提高。通过试验发现:合金在200℃回火后,固溶在基体中的铝能抑制磷向晶界偏聚,使合垒断裂时呈现为穿晶断裂;400℃回火后,由于钼以碳化物形式析出,磷主要偏聚在晶界,造成合金沿晶断裂;600℃回火后,磷主要偏聚在孔隙表面,合金断口呈韧窝状。     

钼钨合金烧结致密化行为

采用原位测量法研究了放电等离子烧结与真空热压烧结Mo–30W合金收缩和致密化行为。研究结果表明:采用放电等离子烧结Mo–30W合金时，1200 ℃以下Mo–30W合金以膨胀为主，1200 ℃以上合金开始剧烈收缩，1600 ℃以上合金收缩趋于停止，在降温阶段合金有较大收缩，温度接近室温时，收缩基本停止。经过1600 ℃放电等离子烧结后合金的相对密度可达93%以上，优于相同温度下真空热压烧结合金的相对密度89.98%。     

钨基重合金注射成形工艺研究

研究了三种钨基重合金的金属注射成形工艺（MIM）,重点研究了脱脂和烧结两个工序,分析了烧结温度对力学性能、断口和显微组织的影响。列举了烧结收缩、力学性能和最佳烧结温度等数据。     

钨基重合金的注射成形工艺

研究了3种钨基重合金的金属注射成形工艺(MIM),重点研究了脱脂和烧结两个工序,分析了烧结温度对机械性能、断口和显微组织的影响,列举了烧结收缩、机械性能和最佳烧结温度等数据。     

Sintering of nano- and ultradispersed mechanically activated W-Ni-Fe powders and the manufacture of ultrahigh-strength heavy tungsten alloys

The structure and mechanical properties of nano- and ultradispersed mechanically activated heavy W-Ni-Fe and W-Ni-Fe-Co tungsten alloys (VNZh and VNZhK alloys, respectively) are studied. Mechanically activated nano- and ultradispersed charge powders are sintered by free sintering (thermally activated) and spark plasma sintering. The dependence of the density of the alloys made of the mechanically activated powders on the sintering temperature is found to have a nonmonotonic character with a maximum corresponding to the optimum sintering temperature. It is shown that an increase in the mechanical activation time and the acceleration of the milling bodies during mechanical activation lead to a decrease in the alloy particle size and the formation of nonequilibrium solid solutions and are accompanied by a decrease in the optimum sintering temperature of heavy tungsten alloys. Ultrahigh-strength tungsten alloys the mechanical properties of which are substantially higher than those of standard coarse-grained analogs are fabricated due to the optimization of the conditions of ball milling and high-rate spark plasma sintering of W-Ni-Fe powders.     

Theory and technology of sintering, thermal and chemicothermal treatment

The studies on the densification of WC-Co alloys in solid-phase sintering are analyzed. It is shown that solid-phase sintering of alloys with tungsten carbide particles smaller than 2.0 µm is characterized by high densification (shrinkage) and results in compact samples in some cases. Shrinkage is established to be nonmonotonic over a wide range of sintering temperatures. There are at least three different stages of densification over the range from room to solidus temperatures. Approximate temperature ranges for densification stages are 100 to 1050 °C, 1050 to 1200 °C, and 1200 °C to the eutectic melting temperature. The stages mainly differ in the extent and rate of shrinkage and in the activation energy. The compaction stages are separated by characteristic temperatures. The most important is 1200 °C, which separates the second and the third stages. The maximum rate of shrinkage is observed mostly at this temperature. The variation of initial WC particles from 5 to 2000 nm does not significantly affect the temperature at which the solid-phase shrinkage rate is maximum. In most cases, there are two maximum rates of shrinkage in WC-Co sintering: one at 1200 ± 30 °C and the other at the solidus temperature.     

W-Re高比重合金的SPS烧结

采用放电等离子烧结(SPS)设备制备了W-Re高比重合金,烧结温度为1800℃,烧结压力为40MPa,保温时间为5min。对SPS烧结的W-Re合金试样进行了密度、硬度等性能测试。采用金相显微镜观察试样的金相组织、晶粒大小。结果表明:采用SPS烧结,可以在较低的温度下实现W-Re合金的致密化,并能有效控制晶粒长大,提高材料的硬度。     

多次烧结对钨铜合金组织与性能的影响

对熔渗法制备的钨铜合金(CuW80)分别进行了3、6、9次烧结。采用金相显微镜、扫描电子显微镜、X射线衍射仪、压汞仪等表征手段,研究了烧结次数对CuW80合金组织和性能的影响。结果表明:随着烧结次数的增加,CuW80合金中钨颗粒直径逐渐增大并连接,铜相分布更加均匀,多次烧结未见新相生成;经过3次烧结后,试样孔隙率由最初的0.5185%变为2.0516%,孔径增加主要集中在0.5~3μm范围内,但9次烧结后试样的孔隙率大大降低;合金硬度由烧结前的HB 204变化至烧结后的HB 188;试样电导率由25.06 mS/m降低至21.92 mS/m;合金密度较烧结前降低了1.2%。     

Distortion in a sintered 7000 series aluminium alloy

Abstract

The 7000 series aluminium alloys processed using elemental powder mixtures are prone to distortion, which is manifest as hourglassing or waisting in cylindrical specimens. By characterising the density distribution using hardness measurements, it is shown that the green density is not evenly distributed through a part, even though aluminium is relatively soft and readily compacted. Because the density equilibrates during sintering, the non-uniform green density leads to distortion. The cause of this distortion is a result of differential shrinkage, which occurs during sintering as well as on solidification during cooling from sintering. Distortion can be controlled by increasing the compaction pressure, which homogenises the green density and does not affect the tensile properties.     

Contemporary Ideas about the Role of the Geometric Factor during Sintering in the Light of Work by M. Yu. Bal'shin

The effect on sintering of two such basic geometric parameters of a powder body as pore size distribution and the magnitude of the interphase specific surface is demonstrated. Nonuniform pore size distribution is the basis of the phenomenon of local volumetric shrinkage during sintering. The amount of interphase surface affects volumetric shrinkage and alloy formation. It is suggested that sintering is a two-stage process. The first stage is sintering of unbound powder system, and the second is sintering of a bound porous body.