The origin of fracture in the I-ECAP of AZ31B magnesium alloy

Magnesium alloys are very promising materials for weight-saving structural applications due to their low density, comparing to other metals and alloys currently used. However, they usually suffer from a limited formability at room temperature and low strength. In order to overcome those issues, processes of severe plastic deformation (SPD) can be utilized to improve mechanical properties, but processing parameters need to be selected with care to avoid fracture, very often observed for those alloys during forming. In the current work, the AZ31B magnesium alloy was subjected to SPD by incremental equal-channel angular pressing (I-ECAP) at temperatures varying from 398 K to 525 K (125 °C to 250 °C) to determine the window of allowable processing parameters. The effects of initial grain size and billet rotation scheme on the occurrence of fracture during I-ECAP were investigated. The initial grain size ranged from 1.5 to 40 µm and the I-ECAP routes tested were A, BC, and C. Microstructures of the processed billets were characterized before and after I-ECAP. It was found that a fine-grained and homogenous microstructure was required to avoid fracture at low temperatures. Strain localization arising from a stress relaxation within recrystallized regions, namely twins and fine-grained zones, was shown to be responsible for the generation of microcracks. Based on the I-ECAP experiments and available literature data for ECAP, a power law between the initial grain size and processing conditions, described by a Zener–Hollomon parameter, has been proposed. Finally, processing by various routes at 473 K (200 °C) revealed that route A was less prone to fracture than routes BC and C

Effect of SiC and GR Reinforcement Particles on the Structure and Functional Properties of Composite Casting E43 MMC Reinforced with SiC Particles

The aim of the study was to describe the structure of composites based on the AlSi7Mg2Sr0.03 alloy matrix reinforced with SiC particles added in an amount of 10% and with a mixture of SiC and GR particles added in a total amount of 20%. Studies of the composite structure, were carried out by scanning electron microscopy (SEM). Based on the results of chemical analysis in microregions, an increased content of elements such as Mg, O and Si and of the precipitates was observed at the interface. In many places in the examined sample, GR particles formed partly disintegrated conglomerates with well developed boundaries. The effect of the content of particles of the reinforcing phase on the functional properties of the composite was investigated during studies of abrasion. The lowest mass loss of 5,33mg was obtained for the AlSi7Mg2Sr0.03 alloy reinforced with 10% SiC particles

Application of X-Ray Diffraction to Analyse Phase Composition of Aluminium Alloys for Plastic Working

An attempt was made to determine phase composition of commercial aluminium alloys using X-ray diffraction. Samples for phase composition analysis were selected from the group of aluminium alloys covered by the EN 573-3:2013 standard [1]. Representative samples were taken from eight groups of alloys with different chemical composition (at least one sample from each group). The diffraction intensity was measured with a standard X-ray diffractometer in Bragg-Brentano geometry in a way that allowed identification of the weakest diffraction peaks. As a results of the performed research it has been shown that X-ray phase analysis can be used to identify the matrix of aluminium alloys, Si and crystalline intermetallic phases such as Mg2Si, Al93.38Cu6.02Fe24Si16.27, Al4.01MnSi0.74, MgZn2, Al17 (Fe3.2Mn0.8)Si2, Al65Cu20Fe15, and Cu3Mn2Al. The detectability limit of the above-mentioned phases is better than 0.5%. The research has also shown that X-ray phase analysis is applicable in the investigation of phase transformations taking place in aluminium alloys

Influence of the Sr and Mg Alloying Additions on the Bonding Between Matrix and Reinforcing Particles in the AlSi7Mg/SiC-Cg Hybrid Composite

The aim of the work was to perform adequate selection of the phase composition of the composite designated for permanent - mould casting air compressor pistons. The hybrid composites based on AlSi7Mg matrix alloy reinforced with mixture of silicon carbide (SiC) and glassy carbon (Cg) particles were fabricated by the stir casting method. It has been shown that the proper selection of chemical composition of matrix alloy and its modification by used magnesium and strontium additions gives possibility to obtain both the advantageous casting properties of composite suspensions as well as good bonding between particles reinforcements and matrix

Influence of the Sr and Mg Alloying Additions on the Bonding Between Matrix and Reinforcing Particles in the AlSi7Mg/SiC-Cg Hybrid Composite

The aim of the work was to perform adequate selection of the phase composition of the composite designated for permanent - mould casting air compressor pistons. The hybrid composites based on AlSi7Mg matrix alloy reinforced with mixture of silicon carbide (SiC) and glassy carbon (Cg) particles were fabricated by the stir casting method. It has been shown that the proper selection of chemical composition of matrix alloy and its modification by used magnesium and strontium additions gives possibility to obtain both the advantageous casting properties of composite suspensions as well as good bonding between particles reinforcements and matrix

Diversification of Intermetallic Zn Phases Growth on Steel During Hot-Dip Galvanizing

The steel substrate formed as the result of oxy-acetylene cutting (OAB) was treated differently - using: softening annealing, grinding and electro-polishing. Investigations were focused on the influence of additional processing on the structure and corrosion resistance of the deposited zinc coating. The hot - dip Zn galvanizing process was conducted in industrial conditions. Parameters were fixed: temperature 457 °C, dipping time 150 s. The coating thickness diversification dependent on the sub-surface steel structure was analysed and compared to the previous results. The correlation between conducted treatment and coatings morphology was determined

Influence of a Substrate Surface on the (Zn) – Coating Formation/ Wpływ Powierzchni Podłoża Na Kształtowanie Się Powłoki (Zn)

The steel substrate was cut by means of different methods, like water jet, laser or oxyacetylene blowpipe. So, some different surfaces (after cutting / without cutting) were subjected to the (Zn) - hot dip galvanizing. The galvanizing process was performed in industrial conditions by applying the constant temperature equal to 457°C, and a dipping time equal to 150 s. The (Zn) - coating morphologies and sub-layer thicknesses were analyzed to explain some expected differences in the coatings formation.W prezentowanej pracy podłoże stalowe cięto stosując różne metody: strumień wody, laser, palnik acetylenowo-tlenowy. W wyniku tego otrzymano zróżnicowaną powierzchnię (po cięciu/bez cięcia), która poddano cynkowaniu ogniowemu. Proces cynkowania wykonywano w warunkach przemysłowych stosując stałe parametry: temperaturę 457°C, czas zanurzenia t=150 s. W trakcie badań analizowano morfologię powłoki cynkowej oraz grubości poszczególnych podwarstw w celu wyjaśnienia różnic w narastaniu powłok

Wpływ powierzchni podłoża na kształtowanie się powłoki (Zn)

The steel substrate was cut by means of different methods, like water jet, laser or oxyacetylene blowpipe. So, some different surfaces (after cutting / without cutting) were subjected to the (Zn) - hot dip galvanizing. The galvanizing process was performed in industrial conditions by applying the constant temperature equal to 457°C, and a dipping time equal to 150 s. The (Zn) - coating morphologies and sub-layer thicknesses were analyzed to explain some expected differences in the coatings formation.W prezentowanej pracy podłoże stalowe cięto stosując różne metody: strumień wody, laser, palnik acetylenowo-tlenowy. W wyniku tego otrzymano zróżnicowaną powierzchnię (po cięciu/bez cięcia), która poddano cynkowaniu ogniowemu. Proces cynkowania wykonywano w warunkach przemysłowych stosując stałe parametry: temperaturę 457°C, czas zanurzenia t=150 s. W trakcie badań analizowano morfologię powłoki cynkowej oraz grubości poszczególnych podwarstw w celu wyjaśnienia różnic w narastaniu powłok

The Production of Material with Ultrafine Grain Structure in Al-Zn Alloy in the Process of Rapid Solidification

In the aluminium alloy family, Al-Zn materials with non-standard chemical composition containing Mg and Cu are a new group of alloys, mainly owing to their high strength properties. Proper choice of alloying elements, and of the method of molten metal treatment and casting enable further shaping of the properties. One of the modern methods to produce materials with submicron structure is a method of Rapid Solidification. The ribbon cast in a melt spinning device is an intermediate product for further plastic working. Using the technique of Rapid Solidification it is not possible to directly produce a solid structural material of the required shape and length. Therefore, the ribbon of an ultrafine grain or nanometric structure must be subjected to the operations of fragmentation, compaction, consolidation and hot extrusion. In this article the authors focussed their attention on the technological aspect of the above mentioned process and described successive stages of the fabrication of an AlZn9Mg2.5Cu1.8 alloy of ultrafinegra in structure designated for further plastic working, which enables making extruded rods or elements shaped by the die forging technology. Studies described in the article were performed under variable parameters determined experimentally in the course of the alloy manufacturing process, including casting by RS and subsequnt fragmentation