Powder Metallurgy Alloys Research Articles

Fatigue Behavior and Surface Sensitivity of Board-Shaped Sample of Powder Metallurgy FGH 96

Powder metallurgy superalloy (P/M superalloy) was developed following the development of turbine engine disc, and it was usually characterized the mechanical behavior using rod specimen . Up to mow, P/M superalloy has not only been the primary material of turbine disc but also the main material of thin plate components. It is insufficient only to carry out mechanical property of rod-shaped samples. In this paper, the fatigue performance and surface sensitivity of powder metallurgy alloys of two kinds of powder (AA powder and PREP powder) were studied. Tensile fatigue tests were carried out for studying the changing law of tensile fatigue behaviors using plate-shaped and rod-shaped samples with shot peening and without shot peening. The surface sensibility of plate specimens was also analyzed according to the fatigue behaviors and crack initiation sites.

Effects of Fe and Ni additions on emerging Al–4·5Cu–1·5Mg powder metallurgy alloy

In recent laboratory studies, a method designed to modify an emerging Al–Cu–Mg powder metallurgy alloy with Fe and/or Ni additions was successfully developed. The objectives of this research were designed to expand upon this work with an emphasis on characterising the industrial processing behaviour and thermal stability of the alloy with and without additions of these transition metals. All powder compacts exhibited an industrial sintering response that mirrored prior laboratory findings thereby confirming commercial viability. Subsequently, tensile specimens were machined from industrially sintered bars, heat treated to the T6 temper and then subjected to various conditions of thermal exposure at temperatures up to 280°C. Differential scanning calorimetry (DSC) data confirmed that Fe/Ni additions reduced the precipitation kinetics of the S-type phases responsible for peak strengthening at temperatures <160°C and thereby enhanced the thermal stability of important tensile properties such as yield strength. At higher temperatures (>200°C), the Fe/Ni additions were less effective with both alloys exhibiting comparable levels of strength degradation.Lors d’études récentes en laboratoire, on a développé avec succès une méthode conçue pour modifier un alliage émergeant de la métallurgie des poudres, Al–Cu–Mg, avec des additions de Fe et/ou de Ni. Cette recherche a pour but d’élargir ce travail avec une emphase sur la caractérisation du comportement du traitement industriel et de la stabilité thermique de l’alliage, avec ou sans additions de ces métaux de transition. Tous les compacts de poudre exhibaient une réponse industrielle de frittage qui reflétait les trouvailles antécédentes en laboratoire, confirmant ainsi la viabilité commerciale. Subséquemment, on a usiné des échantillons pour mesure de résistance à la traction à partir de barres frittées industriellement et on les a traités thermiquement à l’état T6. On a ensuite soumis les échantillons à des conditions variées d’exposition thermique à des températures allant jusqu’à 280°C. Les données de DSC ont confirmé que les additions de Fe/Ni réduisaient la cinétique de précipitation des phases de type S, responsables de l’endurcissement de pointe à des températures <160°C et augmentaient ainsi la stabilité thermique des propriétés importantes de résistance à la traction comme la limite d’élasticité. À des températures plus élevées (>200°C), les additions de Fe/Ni étaient moins efficaces, les deux alliages exhibant des niveaux comparables de dégradation de la résistance.

On the oxidation resistance of a powder metallurgy nickel-based superalloy

To evaluate the influence of reactive minor elements on oxidation resistance of a nickel-based superalloy, 0⋅5w/o Si, and/or 0⋅1w/o Y were added in various combinations to a quaternary powder metallurgy alloy that consisted of a ternary master alloy, Ni–12Cr–9Fe+6w/o Al (w/o). The processing included production of transverse rupture strength (TRS) bars by uniaxial pressing followed by sintering to 1300°C and Gleeble thermo-mechanical deformation to reduce porosity. Sectioned TRS bars were then oxidised (static) at 900°C in air for times up to 1000 h and the influence of the Si/Y additions on oxidation resistance was determined via a combination of weight gain data and microstructural examination. It was found that the addition of 0⋅5w/o Si to the quaternary Ni–Cr–Fe–Al powder metallurgy system provided a measureable improvement in oxidation resistance both in terms of thickness of oxide layer and in overall weight gain. Conversely, 0⋅1w/o Y provided little benefit when added with the Si and was shown to be detrimental in the absence of Si. Interestingly, little difference was noted in final microstructures. Specifically, variation in %γ′ between samples was minimal (58⋅3–61⋅7 v/o) and a distinct precipitate free zone was always present between the oxide and the γ+γ′ matrix.Afin d’évaluer l’influence des oligoéléments réactifs sur la résistance à l’oxydation d’un superalliage à base de nickel, on a ajouté 0⋅5% en poids de Si et/ou 0⋅1% en poids d’Y en combinaisons variées à un alliage quaternaire de la métallurgie des poudres qui consistait en un alliage ternaire maître, Ni–12Cr–9Fe+6% en poids d’Al. Le traitement incluait la production de barres de résistance à la rupture transversale par pressage uniaxe, suivi par le frittage à 1300°C et par la déformation thermomécanique de Gleeble pour réduire la porosité. Les barres sectionnées de TRS étaient ensuite oxydées (en statique) à 900°C à l’air jusqu’à 1000 h et l’influence des additions de Si/Y sur la résistance à l’oxydation était déterminée par l’intermédiaire d’une combinaison de données de gain de poids et d’examen de la microstructure. On a trouvé que l’addition de 0⋅5% en poids de Si au système quaternaire Ni–Cr–Fe–Al améliorait de façon mesurable la résistance à l’oxydation, tant en termes de l’épaisseur de la couche d’oxyde que de son gain global en poids. Réciproquement, 0⋅1% en poids d’Y avait peu de bénéfices lorsque ajouté avec le Si et l’on a montré qu’il était nuisible en absence de Si. De façon intéressante, on notait peu de différence dans les microstructures finales. Spécifiquement, la variation entre les échantillons du% de γ′ était minime (58⋅3 à 61⋅7% en volume) et une zone distincte sans précipités était toujours présente entre l’oxyde et la matrice de γ+γ′.

Development and Processing of Novel Aluminum Powder Metallurgy Materials for Heat Sink Applications

The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacturing. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research, the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In the second, the thermal properties of sintered products were studied in detail. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity, and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99 pct theoretical density and exhibited thermal conductivity that ranged from 179 to 225 W/m K. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and, in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061.

Effect of Zn on Microstructure and Mechanical Properties of Al-Zn-Mg-Cu-Zr Alloy by Powder Metallurgy

In this paper, full-density Al-Zn-Mg-Cu-Zr powder metallurgy (P/M) alloy is prepared by hot-press sintering in vacuum at 600°C. Experiments are conducted to evaluate the effects of Zn additive in the range of 7.2-8.4 wt.% on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Zr alloys. X-ray diffraction (XRD), scanning electron microstructure (SEM) and electron probe micro-analyzer (EPMA), and mechanical properties such as tensile strength are measured. The porosity decreases gradually with increasing of Zn and it achieves 0.01% with a density of 2.95 g/cm3at 8.4% Zn. The tensile strength reaches the maximal value of 436 MPa at 8.4% Zn.

Fracture Toughness of Powder Metallurgy and Ingot Titanium Alloys – A Review

Powder metallurgy (PM) is potentially capable of producing homogeneous titanium alloys at relative low cost compared to ingot metallurgy (IM). There are many established PM methods for consolidating metal powders to near net shapes with a high degree of freedom in alloy composition and resulting microstructural characteristics. The mechanical properties of titanium and its alloys processed using a powder metallurgical route have been studied in great detail; one major concern is that ductility and toughness of materials produced by a PM route are often lower than those of corresponding IM materials. The aim of this paper is to review the fracture toughness of both PM and IM titanium alloys. The effects of critical factors such as interstitial impurities, microstructural features and heat treatment on fracture toughness are also discussed

Effect of doping with refractory rare-earth metals on the structure and properties of Al–5Zn–3Mg alloys produced by powder metallurgy and casting methods

The effect of doping with transition refractory metals on the structure and properties of Al–Zn–Mg alloys produced by different methods is studied. It is ascertained that the strength of cast alloys is increased by scandium and zirconium doping due to the modifying action of scandium that arrests recrystallization and precipitation of the fine-grained phase matrix-coherent Al3(Sc1–x Zr x ) phase; the strength of alloys obtained by powder metallurgy (P/M) methods increases to a smaller extent, in which the ultrahigh cooling rate of melt atomized by high-pressure water plays the basic role in forming the fine-grained structure. The strength of powder metallurgy alloys based on wateratomized powders is substantially higher than that of similar alloys produced by the conventional casting method (standard commercial cast alloys and alloys produced by granular technology). The advantages of P/M alloys over cast alloys are especially prominent in the absence of scandium doping. The highest strength of the P/M alloys with scandium (σb = 651 MPa and σ0.2 = 596 MPa) is shown by Al–5Zn–3Mg–0.5Mn–0.7Zr–0.3Sc. Among the P/M alloys without scandium, the highest strength is shown by Al–5Zn–3Mg–0.85Zr–0.22Cr–0.17Ni–0.15Ti alloy (σb = 618 MPa and σ0.2 = = 553 MPa).

Tribological performance of Al–12Si coatings created via Electrospark Deposition and Spark Plasma Sintering

Spark plasma sintering (SPS) and Electrospark deposition (ESD) were used as two manufacturing routes to create Al–12Si coatings with refined microstructures. The tribological performance of these coatings was tested using a linear reciprocating tribometer. The SPS and ESD coatings were compared to a conventionally as-cast ingot (AC) of Al–12Si to observe the effect of particle refinement and morphology changes. The ESD sample exhibited lower wear rates than the AC and SPS samples. During the wear process, the Al and Si phases on the surface of the AC sample were significantly refined. This refinement led to a microstructure near the surface that was similar to the sample generated by SPS, and therefore showed similar wear rates at the end of testing. Subsurface cracking, which is known to occur in the wear of powder metallurgy alloys, was observed for sample SPS. The refinement of the Al and Si phases achieved for ESD process was much greater than what resulted during the wear of the AC and SPS surfaces and as a result the ESD sample showed lower wear rates throughout the entire test.

Influence Of Mixing Technique On Sintering response Of Binary Aluminium Alloy Powders

Aluminium powder metallurgy (Al-PM) alloys are finding promising applications in many areas such as household appliances, automotive vehicles and many other allied sections where reduction in weight is the primary constraint. In the proposed research, two binary alloy systems Al-X were studied by mixing elemental powders of Aluminium (Al), Tin (Sn) and Magnesium (Mg). Two types of mixing techniques were followed. In one case, elemental powders were blended in a mechanical mixer without any mixing media (A) and another case powders were blended with ball to powder ratio of 10:1 (B). The content in binary premix was varied from 0.4 to 0.8 % Sn (by wt.) and 0.5 to 2 % Mg (by wt.) with base of Aluminium. The blended powders was compacted at 450 MPa followed by sintering in ultra high purity nitrogen atmosphere in tubular sintering furnace at 600 o C. The mixing technique B showed significant influence on increase in hardness by two-

Effects of Fe and Ni additions on an emerging Al–4·4Cu–1·5Mg powder metallurgy alloy:

The effects of Fe and Ni additions to an Al–Cu–Mg powder metallurgy alloy were studied. The transition elements were incorporated through two different approaches, admixed elemental powders and prealloying of the base Al powder. Prealloying proved to be the superior alloying technique as it did not invoke any negative effects on the general sintering behaviour of the baseline alloy. The microstructures of prealloyed materials also exhibited a refined distribution of the aluminide phases formed. These included Al7Cu2Fe, Al7Cu4Ni and Al9FeNi as identified through a combination of SEM/EDS and XRD. The most promising alloy was identified as Al–4·4Cu–1·5Mg–1Fe–1Ni as it exhibited tensile properties that exceeded those of the baseline material. This advantage was also found to persevere after thermal exposure.On a étudié les effets d’additions de Fe et de Ni sur un alliage d’Al–Cu–Mg obtenu par la métallurgie des poudres. On a incorporé les éléments de transition au moyen de deux approches différentes – poudres élémentaires ajoutées ou préalliage de la poudre d’Al de base. Le préalliage était supérieur comme technique d’alliage puisqu’il n’invoquait pas d’effets négatifs sur le comportement général de frittage de l’alliage de référence. La microstructure des matériaux de préalliage exhibait également une distribution raffinée des phases d’aluminures formées. Celles-ci incluaient Al7Cu2Fe, Al7Cu4Ni et Al9FeNi, telles qu’identifiées au moyen d’une combinaison de SEM/EDS et de XRD. L’alliage le plus promettant était l’Al–4·4Cu–1·5Mg–1Fe–1Ni, puisqu’il exhibait des propriétés de traction qui excédaient celles du matériau de référence. On a également trouvé que cet avantage persistait après une exposition thermique.

A three‐dimensional atomistic‐based process zone model simulation of fragmentation in polycrystalline solids

SUMMARYA three‐dimensional atomistic‐based process zone model (APZM) is used to simulate high‐speed impact induced dynamic fracture process such as fragmentation and spall fracture. This multiscale simulation model combines the Cauchy–Born rule, colloidal crystal process model, and micromechanics homogenization technique to construct constitutive relations in both grains and grain boundary at mesoscale. The proposed APZM has some inherent advantages to describe mechanical behaviors of polycrystalline solids. First, in contrast to macroscale phenomenological constitutive models, the APZM takes into account atomistic binding energy and atomistic lattice structure. In particular, the electron density related embedded atom method (EAM) potential has been adopted to describe interatomistic interactions of metallic polycrystalline solids in bulk elements; second, a mixed type of EAM potential and colloidal crystal depletion potential is constructed to describe heterogeneous microstructure in the process zone; third, the atomistic potential in both bulk material and process zone has the same atomistic origin, and hence, the bulk and process potentials are self‐consistent. The simulation of dynamic fracture process of a cylinder made of aluminum powder metallurgy (P/M) alloy during high‐speed impact/penetration is carried out, and numerical results demonstrate that APZM finite element method has remarkable ability to accurately capture complex three‐dimensional fragmentation formation and damage morphology. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Effects of Mg content on aging behavior of Al4CuXMg PM alloy

Starting with elemental (pre-mixed) powders for producing shaped powder metallurgy alloys provides some advantages over a pre-alloyed system. The premixed powders are softer than prealloyed powders and therefore by using premixed powders it is possible to have higher compact densities and within a longer die life. In this research work, elemental aluminum powder was mixed with copper and magnesium in various ratios. They were compacted, sintered and heat treated in order to produce light but strong Al-based powder metallurgy alloys. The main focus of this paper is on the effects of micro to macro scale addition of magnesium on the aging response of Al4Cu alloys. Four per cent Cu gives Al powder metallurgy alloy a good control of sintering and a large space for solution treatment. Minor addition of Mg with little amount of Fe, comes from the based Al and Cu powders, enhances the hardness values of Al4Cu powder metallurgy alloys. Highest hardness value was 118HB obtained from 24h aged Al4Cu2Mg alloy.

Powder metallurgy Al–6Cr–2Fe–1Ti alloy prepared by melt atomisation and hot ultra-high pressure compaction

Al6Cr2Fe1Ti alloy was prepared by melt atomisation into rapidly solidified powder. The powder was compacted using uniaxial hot compression at an ultra-high pressure (6GPa). The samples were pressed at 300, 400 and 500°C. The structure, mechanical properties and thermal stability were examined and compared with those of the commercially available Al12Si1Cu1Mg1Ni casting alloy, which is considered thermally stable. It was shown that the hot compression at ultra-high pressure results in a compact and pore-free material with excellent mechanical properties. The elevated pressing temperatures were found to be effective at increasing the mechanical stability after applying the ultra-high pressure. The results of thermal stability testing revealed that the mechanical properties do not change significantly at high temperature, even after 100h of annealing at 400°C. In addition, the Al6Cr2Fe1Ti alloy exhibited very good creep resistance. A comparison between the commercial Al12Si1Cu1Mg1Ni alloy and the powder metallurgy alloy shows that this alloy has significantly better mechanical properties and thermal stability.

Industrial processing of a novel Al–Cu–Mg powder metallurgy alloy

The objective of this work was to develop an aluminum powder metallurgy (P/M) alloy appropriate for industrial press-sinter technology. An entry in the 2xxx series of aluminum–copper–magnesium alloys was explored for this purpose. Designated as P/M 2324 (Al–4.4Cu–1.5Mg), the sintering response and mechanical properties of the alloy were investigated in laboratory and industrial settings. It was determined that compaction at 400MPa and sintering at 600°C for 20min produced the best properties in the sintered product. Doping with a minor amount of tin (0.2w/o) was found to improve the properties whereas modifications to Cu and Mg concentration produced minimal gains. All tensile properties of P/M 2324 were significantly superior to those of the principal 2xxx series aluminum P/M alloy (AC2014) in current use. These benefits were attributed to a high sintered density (>98% theoretical) that was reproducible in an industrial setting.

Sintering of Titanium with Yttrium Oxide Additions for the Scavenging of Chlorine Impurities

Chloride impurities in titanium powders are extremely difficult to remove and present a long-standing problem in titanium powder metallurgy. We show that the detrimental effects of chlorides on the sintering of titanium can be mitigated with trace additions of yttrium oxide, which has a high affinity for the normally volatile species and forms highly stable oxychloride reaction products. Compacts that would otherwise exhibit gross swelling and excessive porosity due to chloride impurities can be now sintered to near full density by liquid phase sintering. The potency of yttrium oxide additions is observable at levels as low as 500 ppm. The scavenging of chlorine by Y2O3 appears to be independent of alloy composition and sintering regime. It is effective when used with high-chloride powders such as Kroll sponge fines but ineffective when used with powders containing NaCl impurities or during solid-state sintering. The identification of highly potent chlorine scavengers may enable the future development of chloride-tolerant powder metallurgy (PM) alloys aimed at utilizing low-cost, high-chloride powder feedstocks.

Dispersoid strengthening of Al–Cu–Mg P/M alloy utilising transition metal additions

The objective of this research was to devise a means by which dispersoid forming transition metals could be incorporated into press and sinter aluminium powder metallurgy (P/M) alloys. Additions of iron and nickel were explored in this context added as either admixed elemental powders or prealloyed additions into the base aluminium powder. Utilising an Al–2·3Cu–1·6Mg–0·2Sn composition as the base system, elemental additions imparted coarse aluminide phases within the sintered microstructure and diminished the general sintering response of the alloy. The resultant tensile properties of these materials were inferior to those of the unmodified base alloy. Prealloying was much more effective. Using this approach, highly refined distributions of aluminides were achieved without any adverse effects on the compaction or sintering response of the base alloy. A prealloyed addition of 1 wt-% iron was the most effective of those considered as it imparted tangible gains in yield strength and ultimate tensile strength (UTS) to the base alloy.

Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel

The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30 μm prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPa·m1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

The Study on Exchange-Coupled between Nd&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;14&lt;/sub&gt;B Hard Magnetic Phase and α-Fe Soft Magnetic Phase

The uniform of the heat treatment process and NdFeB alloy powder metallurgy technology on the α-Fe soft phase effects. Experimental results show that the uniform of the heat treatment process can significantly reduce the α-Fe soft phase of the content, and the thinning, also found that the remaining α-Fe soft phase sintering and after annealing and hard to deal with after the occurrence of magnetic exchange coupling And its magnetic properties can have a greater impact, so this experiment for the Development of the fourth generation of rare earth permanent magnets laid the foundation.

Fractographic evaluation of high cycle fatigue strength of a high V alloyed powder metallurgy tool steel

The high cycle fatigue strength and the fracture surface morphology of a high V alloyed powder metallurgy tool steel were investigated and connected with microstructure. The inclusion with size above 30 μm was demonstrated to be responsible for the reduction in fatigue strength. The shape and size of inclusion and the stress amplitude affected the position of crack origin in fish eye. Based on fractographic evaluation and statistical analysis, the most harmful inclusions with the largest size proportion for steel A are ∼30 μm, and that of B1, B2 and B3 is roughly 50, 60 and 60 μm respectively. A distinctive granular-like zone with specific morphology was found to be confined in a very small area, suggesting that the fatigue crack propagation was mainly controlled by Paris Law regime. A linear fracture mechanics approach was implemented to evaluate the effect of grain size, yield stress and inclusion size on fatigue strength.

Influence of Tool Material and Surface Roughness on Galling Resistance in Sliding Against Austenitic Stainless Steel

Transfer and accumulation of adhered sheet material, generally referred to as galling, is a major cause for tool failure in sheet metal forming. In the present work, the galling resistance of three different tool materials was evaluated in lubricated sliding against austenitic stainless steel using a SOFS tribometer. All tool materials were prepared to four different surface roughnesses, ranging from a polished surface with R a = 0.05 μm to a ground surface with R a = 0.3 μm. The overall best performance was obtained for polished nitrogen alloyed powder metallurgy (PM) tool steel, where galling was detected only at the highest load evaluated, 700 N. However, for both the D2 type tool steel and nodular iron, best performance was observed for the surface possessing a surface roughness of 0.1 μm. The improved galling resistance for the rougher surfaces was related to filling of grinding scratches with sheet material during the initial stage of sliding, prolonging the development of protruding sheet material on the tools surface. Similar trend was not observed for the PM steel, which was related to width of the scratches originating from the surface preparation, in relation to tool microstructure.