scholarly journals The Casting Rate Impact on the Microstructure in Al–Mg–Si Alloy with Silicon Excess and Small Zr, Sc Additives

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2056
Author(s):  
Evgenii Aryshenskii ◽  
Maksim Lapshov ◽  
Sergey Konovalov ◽  
Jurgen Hirsch ◽  
Vladimir Aryshenskii ◽  
...  
Keyword(s):  
Solid Solution ◽  
Cooling Rate ◽  
Supersaturated Solid Solution ◽  
Solidification Rate ◽  
Crystallization Rate ◽  
Alloying Elements ◽  
Grain Structure ◽  
Transmission Microscopy ◽  
Intermetallic Particles ◽  
Silicon Excess

The study investigates the effect of casting speed on the solidification microstructure of the aluminum alloy Al0.3Mg1Si with and without the additions of zirconium and scandium. Casting was carried out in steel, copper, and water-cooled chill molds with a crystallization rate of 20 °C/s, 10 °C/s, and 30 °C/s, respectively. For each casting mode, the grain structure was investigated by optical microscopy and the intermetallic particles were investigated by scanning and transmission microscopy; in addition, measurements of the microhardness and the electrical conductivity were carried out. An increase in the solidification rate promotes grain refinement in both alloys. At the same time, the ingot cooling rate differently affects the number of intermetallic particles. In an alloy without scandium–zirconium additives, an increase in the ingot cooling rate leads to a decrease in the number of dispersoids due to an increase in the solubility of the alloying elements in a supersaturated solid solution. With the addition of scandium and zirconium, the amount of dispersoids increases slightly. This is because increasing the solubility of the alloying elements in a supersaturated solid solution is leveled by a growth of the number of grain boundaries, promoting the formation of particles of the (AlSi)3ScZr type, including those of the L12 type. In addition, the increase in the crystallization rate increases the number of primary nonequilibrium intermetallic particles which have a eutectic nature.

scholarly journals Improvement of mechanical properties of iron castings via adjusting of solidification rate

2020 ◽  
pp. 17-20
Author(s):  
N. I. Gabelchenko ◽  
A. A. Belov ◽  
N. A. Kidalov ◽  
A. I. Gabelchenko
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Solidification Rate ◽  
Crystallization Rate ◽  
Heat Extraction ◽  
Eutectic Transformation ◽  
Primary Austenite ◽  
Iron Castings ◽  
Alloying Additives ◽  
Air Blowing

The work is devoted to improvement of mechanical properties of iron castings via adjusting of the cooling rate without introduction of alloying additives. The new technological solution is suggested; it can be easily adapted to a casting technology. This solution is based on variation of the cooling rate of iron castings within structurally sensitive solidification intervals. For this purpose, the casting mould was initially cooled after pouring, then heated and cooled again. Cooling of the mould during the period of primary austenite crystal forming led to increase of dendrite crystallization rate and was executed using compressed air. Retarding of the cooling rate during the period of eutectic transformation was provided by the mould heating via burning of exothermic carbon-containing additives introduced in a facing layer of sand-clay moulding mix. Burning reaction is accompanied by heat extraction, what steeply retarded the cooling rate within the interval of eutectic transformation. Consequent acceleration of castings cooling within the interval of eutectoid transformation was achieved via repeated air blowing through a worked reaction layer. Adjusted cooling of iron castings allowed to provide the most favourable solidification conditions, taking into account strictly individual requirements for each structurally sensitive temperature intervals. It led to increase of a volumetric part of primary austenite dendrite crystals, to decrease of eutectic transformation overcooling degree, to forming of graphite eutectics and enlargement of dispersity of pearlite component in iron. Consequently, lowering of widespread iron castings rejects takes place, among them chilling, with simultaneous improvement of metal mechanical properties. As a result, the primary and real structures were varied, what had a positive effect on mechanical properties of casting metal. It is shown that use of solidification rate adjustment led to essential increase of metal tensile strength for the experimental casting.

Precipitation of Phases in Al-Mg-Si-Cu Alloy with Sc and Zr Additions during Heat Treatment

2007 ◽  
Vol 130 ◽  
pp. 163-166 ◽  
Author(s):  
Lidia Lityńska-Dobrzyńska
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Cooling Rate ◽  
Supersaturated Solid Solution ◽  
Ageing Temperature ◽  
Spherical Particles ◽  
Preliminary Heat Treatment ◽  
Complete Dissolution ◽  
Cu Alloy ◽  
Copper Mould

In the present work the sequence of phases in Al-1%Mg-0.6%Si-1%Cu (in wt %) alloys with 0.4%Sc and 0.2%Zr additions during heat treatment has been studied. The investigated alloys were cast into copper mould to ensure high cooling rate during solidification and the retention of Sc and Zr in the supersaturated solid solution. Two−step preliminary heat treatment was applied: the annealing at temperature 300°C or 350°C followed by quenching from 540°C to water. The precipitation of the Q′ and Al3Sc phases has been observed during the first step of annealing. The annealing at 540°C has led to complete dissolution of the Q′ particles and growth of the spherical particles of the Al3Sc phase. The increase of hardness during subsequent ageing at 165°C (typical ageing temperature of the 6xxx alloys) has been caused by the formation of needle-like Q′ phase which coexist with Al3Sc precipitates.

scholarly journals The Effect of Solidification Rate on the Microstructure and Mechanical Properties of Pure Magnesium

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1264
Author(s):  
Murtatha M. Jamel ◽  
Hugo Lopez ◽  
Benjamin Schultz ◽  
Wilkistar Otieno
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Fracture Behavior ◽  
Solidification Rate ◽  
Casting Process ◽  
Grain Structure ◽  
Rockwell Hardness ◽  
Cooling Rates ◽  
Liquid Co2 ◽  
Processing Defects

Magnesium, Mg, has been widely investigated due to its promising potential as magnesium alloys for various applications, particularly as biomedical implantation devices among other medical applications. This work investigates the influence of different cooling rates on the strength of pure Mg. The cooling rates were set to cover a low cooling rate LCR (0.035 °C/s) in an insulated furnace, a moderate cooling rate MCR (0.074 °C/s) in uninsulated-ends furnace, and a high cooling rate HCR (13.5 °C/s) in liquid CO2. The casting process was accomplished using a closed system of melting and cooling due to the reactivity-flammability of magnesium in order to minimize processing defects and increase the safety factor. The as-cast samples were metallographically examined for their microstructure, and properties such as impact strength, hardness, and tension were determined. Increasing the solidification rate from 0.035 °C/s to 0.074 °C/s increased the hardness from 30 to 34 Rockwell Hardness and the UTS from 48 to 67 MPa. A higher solidification rate of 13.5 °C/s further enhanced the hardness to 48 Rockwell Hardness and the UTS to 87 MPa in comparison to the 0.074 °C/s cooling rate. Additionally, the fracture behavior and morphology were investigated. It was found that in general, the mechanical properties tended to improve by refining the grain structure.

Non-Heat Treatable Al-Alloys: Development of Intermetallic Particles during Solidification and Homogenization

2019 ◽  
Author(s):  
Olaf Engler ◽  
Katrin Kuhnke ◽  
Jochen Hasenclever
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Electrical Conductivity ◽  
Al Alloys ◽  
Alloying Elements ◽  
Second Phase ◽  
Phase Selection ◽  
Industrial Processing ◽  
Intermetallic Particles ◽  
Second Phase Particles

The materials properties of Al-alloys are controlled by the added alloying elements and by the processing conditions through the resulting materials microstructure. An important aspect in the description of the microstructure is the constitution of the material in terms of alloying elements in solid solution and, in turn, volume, size, morphology, and species of second-phase particles. These constitutional characteristics, conveniently summarized as microchemistry, have an impact on physical properties like thermal or electrical conductivity and on mechanical properties including strength and formability of Al-alloys. In the present article, we summarize the phase selection upon solidification and the changes in microchemistry during subsequent homogenization annealing during conventional industrial processing of non-heat-treatable Al wrought alloys.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

Direct Observation of Monolayer Zones in Al-wt 4% Cu

1990 ◽  
Vol 48 (1) ◽  
pp. 14-15
Author(s):  
B. Jouffrey ◽  
D. Dorignac ◽  
A. Bourret
Keyword(s):  
Solid Solution ◽  
Synchrotron Radiation ◽  
Direct Observation ◽  
Supersaturated Solid Solution ◽  
Original Model ◽  
X Ray ◽  
Image Position

Since the early works on GP zones and the model independently proposed by Preston and Guinier on the first steps of precipitation in supersaturated solid solution of aluminium containing a few percent of copper, many works have been performed to understand the structure of different stages in the sequence of precipitation.The scheme which is generally admitted can be drawn from a work by Phillips.In their original model Guinier and Preston analysed a GP zone as composed of a single (100) copperrich plane surrounded by aluminum atomic planes with a slightly shorter distance from the original plane than in the solid solution.From X-ray measurements it has also been shown that GP1 zones were not only copper monolayer zones. They could be up to a few atomic planes thick. Different models were proposed by Guinier, Gerold, Toman. Using synchrotron radiation, proposals have been recently made.

Metallographic analysis of M2 high speed steel granules

2019 ◽  
pp. 78-85
Author(s):  
L. E. Afanasieva
Keyword(s):  
Solid Solution ◽  
Cellular Structure ◽  
High Speed ◽  
Solution Structure ◽  
Supersaturated Solid Solution ◽  
High Speed Steel ◽  
Metallographic Analysis ◽  
M2 High Speed Steel ◽  
Melt Composition

The article is devoted to the metallographic analysis of the M2 high-speed steel granules. The study is based on the investigation of the microstructure of the M2 high-speed steel granules obtained by melt atomization. It is demonstrated that granules of similar size can harden both by chemically separating and chemically non-separating mechanism. These last ones have supersaturated solid solution structure of the liquid melt composition, a dispersed dendritic-cellular structure and an increased microhardness HV = 10267±201 MPa.

Microstructure evolution of YSZ/Al2O3 supersaturated solid solution

2021 ◽  
Vol 549 ◽  
pp. 149260
Author(s):  
Yongdong Yu ◽  
Yongting Zheng ◽  
Xudong Liu ◽  
Yuchen Yuan ◽  
Wanjun Yu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Microstructure Evolution ◽  
Supersaturated Solid Solution

Hardenability of Medium Carbon Cr-Mn-Mo Alloyed Steels

2019 ◽  
Vol 946 ◽  
pp. 341-345
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Cooling Rate ◽  
Structural Steels ◽  
Alloying Elements ◽  
Metallographic Analysis ◽  
Medium Carbon ◽  
Austenite Transformation ◽  
Continuous Cooling ◽  
Different Content ◽  
Cct Diagrams

Three medium carbon Cr-Mn-Mo structural steels with different content of alloying elements were studied. The austenite transformation during continuous cooling was investigated using dilatometer and metallographic analysis. The CCT diagrams were plotted showing the effect of the increased alloying elements content and B and Nb micro-alloying on the hardenability of the studied steels. The hardness dependences on the cooling rate were obtained.

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