Effect of Low Strain Rate on Formability of Aluminium Alloy

Effect of low strain rate on formability of aluminium alloy 2014 by means of torsion test was performed. The presented experimental results exhibit decrease of the ductility with increase and decrease of ε and T, respectively, and optimal values of , ε T are thus obtained

The Effects of Chemical Composition on Soft Magnetic Materials Behaviour

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Wysokotemperaturowe zachowanie stopu aluminium EN AW 2014

The high-temperature behaviour of aluminium alloy EN AW 2014 was investigated in a wide range of deformation temperatures and strain rates. The influence of strain rate and temperature on the peak stress was analysed using the conventional constitutive equation (relating strain rate, flow stress, and temperature) and by means of precise definition of the peak stress value, in the non-linear regression model. Moreover, a study on apparent activation energy of EN AW 2014 stabilized by zirconium was carried out using Arrhenius-type plot. The stress-strain curves exhibit rapid increase up to the peak value followed by a gradual softening up to the material fracture, without the steady state usually observed before the fracture. In terms of formability maps, the presented experimental results exhibit a decrease of ductility, respectively with an increase of strain rate and a decrease of temperature, respectively.Wysokotemperaturowe zachowanie stopu aluminium EN AW 2014 badane było w szerokim zakresie temperatur i predkości odkształcenia. Wpływ prędkości odkształcenia i temperatury na maksymalne naprężenie analizowany był z użyciem konwencjonalnego podstawowego równania (wiazacego predkość odkształcenia, naprezenie płyniecia i temperature) oraz za pomocą precyzyjnej definicji wartości maksymalnego naprężenia w modelu regresji nieliniowej. Ponadto, analiza obserwowanej energii aktywacji stopu EN AW 2014 stabilizowanego cyrkonem przeprowadzono z użyciem wykresu typu Arrheniusa. Krzywe naprężenie-odkształcenie wykazują gwałtowny wzrost do maksymalnego naprężenia, po którym następuje stopniowe mięknięcie aż do zerwania materiału, bez obszaru stałego zwykle obserwowanego przed zerwaniem. Jesli chodzi o mapy plastycznosci, przedstawione wyniki doświadczalne wykazują spadek plastycznosci, odpowiednio ze wzrostem szybkości odkształcenia oraz ze spadkiem temperatury

Analysis of Densification Process and Structure of PM Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn Alloys

The paper is focused on the role of the pressing pressure on the densification behaviour of PM aluminium alloys. Commercially aluminium based powders Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn were used as materials to be investigated. The apparent density of the powder mixes was determined according to MPIF St. 04. A set of cylinder test specimen 55X10X10 mm3 was uniaxially pressed in a floating hardened steel die. Compaction pressures ranged from 50 MPa up to 700 MPa. Considering the densification of metal powders in uniaxial compaction, quantification of aluminium compaction behaviour was performed. The compressibility behaviour was evaluated, considering the effect on specimens, as well as on their microstructure. The development of compressibility values with pressing pressure enables to characterize the effect of particles geometry and matrix plasticity on the compaction proces

Rola niejednorodności mikrostruktury w magnetycznie miękkich kompozytach z dodatkiem stopu aluminium

The paper focuses on the effect of both the aluminium alloy addition and microstructural inhomogeneties on the magnetic behaviour of soft magnetic materials tested at low frequencies. The IIPC material (base on the commercial Somaloy 1P powder) has been blended with different amounts of commercially aluminium alloy Alumix 321 (0, 5 and 10 wt %). Specimens with a different green density were obtained by pressing at a pressure in the range from 400 to 800 MPa. Different thermal treatments (in air or nitrogen at the maximum temperature of 500ºC for 30 min) were carried out on the evaluated systems. The microstructure investigation revealed that for materials with high aluminium alloy contents, pores are located nearby or around the aluminium alloy particles. The heat treatment regime resulted in a coarse-grained structure with a small number of inclusions within the grains and at the grain boundaries. The comparison of the results indicated that the magnetic properties were considerably dependent on the microstructural inhomogeneities.Przedmiotem pracy jest wpływ dodatku stopu aluminium oraz niejednorodności mikrostruktury na właściwości magnetyczne magnetycznie miękkich materiałów badanych przy niskich częstotliwościach. Materiał IIPC (na bazie komercyjnego proszku Somaloy 1P) został zmieszany z różnymi ilościami komercyjnego stopu aluminium ALUMIX 321 (0, 5 i 10% wag.). Próbki o różnych gęstościach nasypowych prasowano stosując ciśnienie w zakresie od 400 do 800 MPa. Zastosowano różne obróbki cieplne (w powietrzu i azocie) ustalając maksymalną temperaturę 500ºC. Badania mikrostruktury pokazały, że dla materiałów o wysokiej zawartości stopu aluminium, pory sa w pobliżu lub otaczają cząstki stopu aluminium. W wyniku obróbki cieplnej tworzy się gruboziarnista struktura z minimalną liczbą wtraceń wewnątrz ziaren i na ich granicach. Porównanie wyników pokazuje, ąe właściwości magnetyczne zaleza w znacznym stopniu od niejednorodności mikrostruktury

The Porosity Evaluation during ECAP in Aluminium PM Alloy

The main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (Al-Mg-Si-Cu-Fe) was used as investigated material. After applying different pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventilated furnace at 400C for 60 min. Sintering was carried out in a vacuum furnace at 610C for 30 min. The specimens were processed by single equal channel angular pressure pass. A significant disadvantage of powder metallurgy processing methods is the presence of porosity. Pores act as crack initiators and, due to their presence, the distribution of stress is inhomogeneous across the cross-section and leads to reduction of the effective load bearing area. The equal channel angular pressure process, causing stress distribution in deformed specimens, made the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores. The proposed safety diagram includes the combined effect of stress and strain behaviour during equal channel angular pressure. The "safety line" eliminates and quantifies the effect of large pores as a potential fracture initiation sites with respect to the mechanical viewpoint

Analysis of the Fracture Surfaces of New Development Insulated Iron Powder Compounds

Goal of the present paper is the analysis of the fracture surfaces of an Insulated Iron Powder Compound (IIPC) with different additions of aluminium alloy (0.25, 0.5 and 0.75 wt.%), in order to improve the mechanical properties, evaluated as the transverse rupture strength (TRS) with sufficient magnetic properties (mainly represented by the iron loss and coercivity force). Investigation of microstructure and porosity development concluded that improvements in bending strength and impact values require the reduction of surface oxides during the heat treatment, in order to get a proper load bearing area between the adjacent particles