Features of structure formation in Al–Fe–Mn alloy during crystallization at different cooling rates

2020 ◽  
pp. 76-86
Author(s):  
I. S. Loginova ◽  
M. V. Sazerat ◽  
N. A. Popov ◽  
A. V. Pozdniakov ◽  
A. N. Solonin
Keyword(s):  
Yield Strength ◽  
Cooling Rate ◽  
Room Temperature ◽  
Primary Crystallization ◽  
Additive Technologies ◽  
Laser Melting ◽  
Cooling Rates ◽  
Average Cell ◽  
Alloy Microstructure ◽  
Primary Crystals

The paper studies specific features of the Al–2.5%Fe–1.5%Mn alloy microstructure formation depending on the cooling rate during casting and laser melting. As-cast microstructure analysis showed that with an increase in the cooling rate during crystallization from 0.5 to 940 K/s, the primary crystallization of the Al6(Mn,Fe) phase is almost completely suppressed with the non-equilibrium eutectic volume increasing to 43 %. The Al–2.5%Fe–1.5%Mn alloy microstructure after laser melting features by the presence of dendritic-type aluminum matrix crystals with an average cell size of 0.56 μm surrounded by an iron-manganese phase of eutectic origin with an average plate size of 0.28 μm. The primary crystallization of the Al6(Mn,Fe) phase is completely suppressed. Such a microstructure is formed at cooling rates of 1.1·104 to 2.5·104 K/s, which corresponds to the cooling rates implemented in additive technologies. Regions consisting of Al6(Mn,Fe) phase primary crystals formed by the epitaxial growth mechanism were revealed at the boundary between the track and the base metal and at the remelting boundary. The smaller the eutectic plates and dendritic cell located in the epitaxial layer, the more disperse the primary crystals in the remelting zone. The Al–2.5%Fe–1.5%Mn alloy after laser melting has high hardness at room temperature (93 HV) and good thermal stability after heating up to 300 °C (hardness slightly decreases to 85 HV), and its calculated yield strength is 227 MPa. Combined with the ultra-fine microstructure formed, high processibility during laser melting, hardness at room temperature, and high calculated yield strength, Al–2.5%Fe–1.5%Mn is a promising alloy for use in additive technologies.

Effect of laser inclination angle on mechanical properties of Hastelloy X processed by selective laser melting

2021 ◽  
Vol 63 (1) ◽  
pp. 10-16
Author(s):  
Zong Xuewen ◽  
Zhang Jian ◽  
Fu Hanguang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Temperature Field ◽  
Yield Strength ◽  
Cooling Rate ◽  
Selective Laser Melting ◽  
Inclination Angle ◽  
Laser Melting ◽  
Cooling Rates ◽  
Hastelloy X

Abstract Selective laser melting at various laser inclination angles was used to prepare Hastelloy X alloy specimens. The morphology, fracture, tensile strength, stress, and strain of Hastelloy X alloy specimens were studied using optical microscopy, scanning electron microscopy, and a tensile tester. The temperature field of the manufacturing process was analyzed based on finite element analysis, and the internal relationship between the temperature field and the process was constructed in terms of cooling speed. The results show that the temperature field is a dynamic process with a high cooling rate; the average cooling rate reaches 3.23 × 106 °C × s−1. The greater the inclination angle, the greater the thermal gradient, resulting in higher cooling rates. Due to the cross-influence of grain refinement at high cooling rates and residual stress, the tensile strength and yield strength of Hastelloy X alloy showed first increasing and then decreasing trends with respect to inclination angle. However, at an inclination angle of 30°, the voids and crack defects of Hastelloy X alloy fractures were reduced, and the tensile strength and yield strength reached 881.38 and 701.60 MPa, respectively. At this angle, the mechanical properties were excellent and met the requirements of the aviation industry.

Influence of Cooling Rate after High Temperature Annealing on Deep Levels in High-Purity Semi-Insulating 4H-SiC

2007 ◽  
Vol 556-557 ◽  
pp. 371-374 ◽  
Author(s):  
Andreas Gällström ◽  
Björn Magnusson ◽  
Patrick Carlsson ◽  
Nguyen Tien Son ◽  
Anne Henry ◽  
...  
Keyword(s):  
High Temperature ◽  
Cooling Rate ◽  
High Purity ◽  
Room Temperature ◽  
Deep Levels ◽  
High Temperature Annealing ◽  
Cooling Rates ◽  
Silicon Vacancy

The influence of different cooling rates on deep levels in 4H-SiC after high temperature annealing has been investigated. The samples were heated from room temperature to 2300°C, followed by a 20 minutes anneal at this temperature. Different subsequent cooling sequences down to 1100°C were used. The samples have been investigated using photoluminescence (PL) and IV characteristics. The PL intensities of the silicon vacancy (VSi) and UD-2, were found to increase with a faster cooling rate.

Room Temperature Tensile Ductility in Powder Processed B2 FeAi Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
M. A. Crimp ◽  
K. M. Vedula ◽  
D. J. Gaydosh
Keyword(s):  
Fracture Surface ◽  
Yield Strength ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Yield Stress ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Strengthening Mechanism ◽  
General Yielding

AbstractIt has been shown that it is possible to obtain significant room temperature tensile ductility in FeAl alloys using iron-rich deviations from stoichiometry. A comparison of the room temperature tensile and compressive behaviors of Fe−50at% Al and Fe−40at% Al shows that FeAl is brittle at higher Al contents because it fractures along grain boundaries before general yielding. Lower aluminium contents reduce the yield stress substantially and hence some ductility is observed before fracture.Addition of boron results in measurable improvements in ductility of Fe−40at% Al and is accompanied by an increase in transgranular tearing on the fracture surface, suggesting a grain boundary strengthening mechanism.Increasing the cooling rate following annealing at 1273 K results in a large increase in the yield strength and a corresponding decrease in ductility.

Metastable Hexagonal Modifications of the NbCr2 Laves Phase as Function of Cooling Rate

2008 ◽  
Vol 1128 ◽  
Author(s):  
Jochen Aufrecht ◽  
Andreas Leineweber ◽  
Eric Jan Mittemeijer
Keyword(s):  
Cooling Rate ◽  
Room Temperature ◽  
Laves Phase ◽  
Cooling Rates ◽  
Arc Melting

AbstractIn as-cast ingots produced by arc-melting, several metastable polytypic modifications of NbCr2 were found additional to the cubic C15 phase stable at room temperature: C14, C36 and 6H-type structures, often highly faulted and/or intergrown. Strikingly, these phases had formed at locations of the specimen which had experienced a relatively low cooling rate, whereas the C15 phase was formed preferentially in regions which had experienced the highest cooling rates.

Continuous Annealing Process and Microstructure Property of 1200mpa High Strength Steel by Ultrafast Cooling

2014 ◽  
Vol 788 ◽  
pp. 351-356 ◽  
Author(s):  
San Chuan Yu ◽  
Ren Bo Song ◽  
Qi Feng Dai ◽  
Zhe Gao
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Cooling Rate ◽  
Room Temperature ◽  
Annealing Temperature ◽  
High Strength ◽  
Continuous Annealing ◽  
Experimental Steel ◽  
Steel Increase ◽  
Ultrafast Cooling

The different dilatometric curves of continuous cooling transformation have been determined by DIL805 thermal mechanical simulate, through metallographic and hardness method to study the effect of different cooling rate on the microstructure of transition. The critical point Ac1 and Ac3 of the tested steel are 709°C and 865°C. With the increase of cooling rate, the hardness of the steel and the content of martensite increase. In the laboratory conditions, the steel in this experiment was heated to 780°C, 800°C, 820°C, 840°C and 860°C, for 80s, then slowly cooled to 680°C, and water quenched to room temperature finally. The aging temperature was 240°C for 300s, and the last the sample was air cooled to room temperature. The results show that the microstructure of the annealed experimental steel belongs to martensite and ferrite. With the increase of annealing temperature, the content of martensite, the tensile strength and yield strength of the experimental steel increase, and the elongation decreases continuously. The sample was annealed at 800°C for 80s, then slowly cooled to 680°C and finally water quenched to room temperature. After overaging at 240°C, the samples were obtained with high mechanical properties. The tensile strength, yield strength and elongation are 1223MPa, 605MPa and 9.2%, respectively.

scholarly journals Effect of Cooling Rate on Phase and Crystal Morphology Transitions of CaO–SiO2-Based Systems and CaO–Al2O3-Based Systems

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 62 ◽  
Author(s):  
Mei Leng ◽  
Feifei Lai ◽  
Jiangling Li
Keyword(s):  
Cooling Rate ◽  
Mold Flux ◽  
Crystal Morphology ◽  
Confocal Scanning Laser Microscopy ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Mold Fluxes ◽  
Confocal Scanning ◽  
Confocal Scanning Laser ◽  
Primary Crystals

The phase and crystal morphology transitions of two typical types of mold fluxes were investigated fundamentally using differential scanning calorimetry (DSC) and confocal scanning laser microscopy (CSLM) techniques. For the traditional CaO–SiO2–CaF2-based mold flux, different cooling rates can change the phases and the crystal morphologies. Faceted cuspidine and CaSiO3 are co-precipitated when the cooling rate is less than 50 °C·min−1. The phases transform from Ca4Si2O7F2 and CaSiO3 to Ca4Si2O7F2 at the cooling rate of 50 °C·min−1. Cuspidine shows four different morphologies: faceted shape, fine stripe, fine stripe dendrite, and flocculent dendrite. The crystalline phases of CaAl2O4 and Ca3B2O6 are co-precipitated in the CaO–Al2O3-based mold flux. Neither the phases nor the crystal morphologies change in the low cooling rate range (5 °C·min−1 to 50 °C·min−1). With decreasing temperature, the morphology of CaAl2O4 firstly becomes dendritic, and then the dendritic quality gradually changes to a large-mesh blocky shape at the cooling rates of 100 °C·min−1, 200 °C·min−1, and 500 °C·min−1. Different cooling rates do not show an obvious impact on the morphology transition of CaAl2O4. The strong crystallization ability and large rate of crystallization affect the control of the heat transfer of the CaO–Al2O3-based mold flux during casting. The big morphology difference between primary crystals of the CaO–SiO2–CaF2-based mold flux and the CaO–Al2O3-based mold flux is probably one of the biggest factors limiting lubrication between the CaO–Al2O3-based mold flux and high-Al steel during casting.

Effects of Cooling Rate on the Microstructure and Room Temperature Tensile Properties of Orthorhombic Ti-22Al-21Nb-1Ta-1W Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 817-820
Author(s):  
Dong Luo ◽  
Yu You Cui ◽  
Rui Yang
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Cooling Rate ◽  
Room Temperature ◽  
Lamellar Microstructure ◽  
High Temperature Mechanical Properties ◽  
Solution Treated ◽  
Room Temperature Yield Strength ◽  
Transus Temperature ◽  
O Phase

In order to improve high temperature mechanical properties of Ti2AlNb based alloys, alloying with a combination of Ta and W was studied in the on-going work. The effects of cooling rate after solution heat treatment on the room temperature mechanical properties have been reported in this paper. All samples were solid solution treated at near β transus temperature, cooled at different cooling rates, and then aged at subtransus temperature. Experimental results showed that, with increasing cooling rate, room temperature yield strength decreased sharply to a minimum value, and then increased. Change of elongation exhibits a trend opposite to yield strength. Microstructure of the alloy varied from near lamellar to lamellar plus Widmanstätten, and then to full Widmanstätten structure with the increase of cooling rate, and the faster the cooling rate, the finer the laths of the O phase. The samples with near lamellar microstructure obtained at the cooling rate of 6oC/min possess the best ductility but relatively low yield strength.

Phase Transformation Rule, Microstructure and Properties of JG590 High Strength Steel

2007 ◽  
Vol 561-565 ◽  
pp. 29-32
Author(s):  
Yong Feng ◽  
Wei Hua Sun
Keyword(s):  
Tensile Strength ◽  
Phase Transformation ◽  
Yield Strength ◽  
Cooling Rate ◽  
High Strength Steel ◽  
High Strength ◽  
Steel Plates ◽  
Transformation Rule ◽  
Cooling Rates ◽  
Iron And Steel

The phase transformation rule, microstructures and properties of JG590 high strength steel produced in Jinan Iron and Steel Co. ltd. have been investigated in this paper. When the chemical composition of steel are given, the cooling rates after finished rolling affect on the properties of steel greatly. The yield strength and tensile strength increasing, the elongation and reduction of area decreasing as increasing of cooling rates after rolling. The main cause is due to appearance and increasing of Bainite and Martensite other than Ferrite and Pearlite in room temperature. The finished rolling temperature have distinct effects upon the mechanical properties of steel plates. Finished rolling at different temperature with the 0.5°C/s cooling rate, the tensile strength vary in 599-698MPa, the yield strength changed from 412 MPa to 536MPa. The elongation is between 30.4-40.5%. But when finished rolling at different temperature with the 2.0°C/s cooling rate, the tensile strength vary in 747-784MPa, the yield strength changed from 441 MPa to 601MPa. The strength index can both meet the requirements of employ. But the elongation is only 18.7-24.5%. This is related with production of lots of Bainite microstructure more than 2°C/s cooling rate. In the procedure of manufacture of JG590 high steel, the quickly cooling rate should be avoided to keep suitable microstructure and good elongation and toughness.

scholarly journals Microstructures and mechanical properties of austenitic light-weight steels, and prediction of property distribution in large-scale slab

2020 ◽  
Vol 58 (12) ◽  
pp. 830-842
Author(s):  
Tae-Ha Kim ◽  
Yoon Suk Choi ◽  
Kyeong-Won Kim ◽  
Seong-Jun Park ◽  
Jun Young Park ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Cooling Rate ◽  
Large Scale ◽  
Air Cooling ◽  
Light Weight ◽  
Water Cooling ◽  
Absorbed Energy ◽  
Cooling Rates ◽  
Microstructures And Mechanical Properties

The effects of the cooling rate, after solution heat treatment, on the microstructures and mechanical properties of Fe-22Mn-8Al-0.8C-0.02Nb (low carbon) and Fe-20Mn-8Al-1.1C-0.1Nb (high carbon) light-weight steels were systematically investigated. The cooling process was controlled to achieve six different cooling rates, ranging from -0.016 to -465.1 <sup>o</sup>C/s. Under the slowest cooling rate (furnace cooling), intra-granular and inter-granular precipitations of <i>κ</i>-carbides were observed throughout the austenite grains. The higher the C content was, the larger the size of the inter-granular <i>κ</i>-carbides was. The formation of <i>κ</i>-carbides resulted in an increase in yield strength, and a decrease in elongation and impact absorbed energy. In the Fe-20Mn-8Al1.1C-0.1Nb, the inter-granular precipitation of <i>κ</i>-carbides caused a drastic decrease in the impact absorbed energy and the inter-granular brittle fracture. To predict the distribution of yield strength and impact absorbed energy at production scale (a 10-ton scale slab), finite element analysis was conducted for water cooling and air cooling conditions. The average cooling rates at the center of the slab under water cooling and air cooling were predicted to be -0.126 and -0.031 <sup>o</sup>C/s, respectively. Based on predicted cooling rates, the distribution of mechanical properties was determined. The prediction suggested that a large-scale slab of the light-weight steel with low C content would have good toughness at the center of the slab regardless of cooling condition.

scholarly journals A novel physics-based and data-supported microstructure model for part-scale simulation of laser powder bed fusion of Ti-6Al-4V

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jonas Nitzler ◽  
Christoph Meier ◽  
Kei W. Müller ◽  
Wolfgang A. Wall ◽  
N. E. Hodge
Keyword(s):  
Selective Laser Melting ◽  
Microstructure Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Laser Melting ◽  
Cooling Rates ◽  
Powder Bed ◽  
Proposed Model ◽  
Microstructure Model ◽  
Transformation Diagrams

AbstractThe elasto-plastic material behavior, material strength and failure modes of metals fabricated by additive manufacturing technologies are significantly determined by the underlying process-specific microstructure evolution. In this work a novel physics-based and data-supported phenomenological microstructure model for Ti-6Al-4V is proposed that is suitable for the part-scale simulation of laser powder bed fusion processes. The model predicts spatially homogenized phase fractions of the most relevant microstructural species, namely the stable $$\beta $$ β -phase, the stable $$\alpha _{\text {s}}$$ α s -phase as well as the metastable Martensite $$\alpha _{\text {m}}$$ α m -phase, in a physically consistent manner. In particular, the modeled microstructure evolution, in form of diffusion-based and non-diffusional transformations, is a pure consequence of energy and mobility competitions among the different species, without the need for heuristic transformation criteria as often applied in existing models. The mathematically consistent formulation of the evolution equations in rate form renders the model suitable for the practically relevant scenario of temperature- or time-dependent diffusion coefficients, arbitrary temperature profiles, and multiple coexisting phases. Due to its physically motivated foundation, the proposed model requires only a minimal number of free parameters, which are determined in an inverse identification process considering a broad experimental data basis in form of time-temperature transformation diagrams. Subsequently, the predictive ability of the model is demonstrated by means of continuous cooling transformation diagrams, showing that experimentally observed characteristics such as critical cooling rates emerge naturally from the proposed microstructure model, instead of being enforced as heuristic transformation criteria. Eventually, the proposed model is exploited to predict the microstructure evolution for a realistic selective laser melting application scenario and for the cooling/quenching process of a Ti-6Al-4V cube of practically relevant size. Numerical results confirm experimental observations that Martensite is the dominating microstructure species in regimes of high cooling rates, e.g., due to highly localized heat sources or in near-surface domains, while a proper manipulation of the temperature field, e.g., by preheating the base-plate in selective laser melting, can suppress the formation of this metastable phase.

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