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

Mikrostruktura, mehanička svojstva i greške na sinterovanom čeliku Fe-3Mn-0.7C

Mechanical properties of Fe-3Mn-0.7C sintered steel were determined in tension and in bending following laboratory and industrial sintering at the temperatures of 1120, 1180 and 1200 °C in a H2-rich atmospheres with the dew points of -33 °C and/or - 30 °C and -55 °C and/or - 60 °C. The microstructure of sintered specimens is complex and heterogeneous, formed by products of the diffusive and non-diffusive transformations. The highest strength properties of the tested alloy were recorded after sintering at 1200 °C in dry atmosphere: R0.2 = 490 MPa, Rm = 642 MPa, bend strength of 1256 MPa, apparent hardness of 207 HV10, tensile and maximum bend strains were 1.02 and 3.6 %. The reproducibility of tensile and bend strengths data was high, characterised by Weibull module, m, of 12 - 38. The large pores or their agglomerates (50 - 70 µm in size) act as the failure originating sites in the tensile and bend specimens.Mehanička svojstva čelika Fe-3Mn-0.7C, sinterovanog u laboratoriju i pogonu na temperaturi od 1120, 1180 i 1200 °C u atmosferi bogatoj vodikom (H2) s rosištima od -33, i/ili -30 i -35 i/ili -60 °C, određena su na vlak i na savijanje. Mikrostruktura uzoraka je kompleksna i heterogena, oblikovana je proizvodima difuzivnih i nedifuzivnih transformacija. Najbolja svojstva čvrstoće testirane slitine zabilježena su nakon sinterovanja na 1200 °C u suhoj atmosferi: R0.2 = 490 MPa, Rm 642 MPa, čvrstoća na savijanje od 1256 MPa, prividna čvrstoća od 207 HV 10, naprezanje na vlak i maksimalna naprezanja na savijanje su bila 1.02 i 3.6 %. Stupanj ponavljanja podataka o čvrstoći na vlak i na savijanje je bio visok i okarakteriziran Weibulovim modulom, m, od 12-38. Velike pore, ili njihovi aglomerati (dimenzije 50 - 70 µm) imaju ulogu grešaka originalnih veličina na uzorcima za ispitivanje na vlak i savijanje

ARMORED ELEMENTS BY MEANS OF POWDER METALLURGY: APPLIED STRESSES, FRACTURE MECHANISMS AND SURFACES

The main aim of this work is to demonstrate the inter-dependencies between chemical composition, mechanical properties and fracture mechanisms to high-speed impacts of a selected series of P/M products. Materials tested have been designed to withstand the stresses produced by ballistic impacts, and processed by powder metallurgy techniques, producing two systems. The compositions were based on Distaloy AE and Astaloy CrL as main powders. The sintering treatment has been carried out in vacuum furnace, following the debinding phase done by the use of a dedicated furnace filled by nitrogen atmosphere. After sintering, the obtained samples had been tempered, using a cycle integrated to sintering. Characterizations were focused on assessment of fracture surfaces, microstructures, quantification of impact energy, hardness and density, followed by evaluation of the behaviour of the materials obtained towards high speed stresses connected to ballistic impacts

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

ARMORED ELEMENTS BY MEANS OF POWDER METALLURGY: APPLIED STRESSES, FRACTURE MECHANISMS AND SURFACES

The main aim of this work is to demonstrate the inter-dependencies between chemical composition, mechanical properties and fracture mechanisms to high-speed impacts of a selected series of P/M products. Materials tested have been designed to withstand the stresses produced by ballistic impacts, and processed by powder metallurgy techniques, producing two systems. The compositions were based on Distaloy AE and Astaloy CrL as main powders. The sintering treatment has been carried out in vacuum furnace, following the debinding phase done by the use of a dedicated furnace filled by nitrogen atmosphere. After sintering, the obtained samples had been tempered, using a cycle integrated to sintering. Characterizations were focused on assessment of fracture surfaces, microstructures, quantification of impact energy, hardness and density, followed by evaluation of the behaviour of the materials obtained towards high speed stresses connected to ballistic impact

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