Wyniki wyszukiwania - Biblioteka Nauki

1

Elastic Constants by Resonant Ultrasound Spectroscopy – Application to Thermoelectrics and Aluminum Alloys

100%

Klobes B.

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2019

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tom nr 112

60--68

EN

Resonant ultrasound spectroscopy is a non-destructive technique for determining the elastic constants of a material. In the context of thermoelectric materials, elastic constants can be used to investigate the speed of sound and, thus, the lattice thermal conductivity of a substance. For Mg2Si-Mg2Sn solid solutions, a possible connection between shear modulus and band convergence can be assumed in that way. Moreover, the rather low speed of sound in this system points towards a high contribution of optical phonons to thermal conductivity. Additionally, significant resonance frequency shifts are observed during natural aging of technical Al-Cu-Mg and Al-Mg-Si alloys, which are proposed to assist investigation of the early stages of clustering in the future.

2

Identification and analysis of intermetallic phases in age-hardened recycled AISi9Cu3 cast alloy

81%

Hurtalová L. , Tillová E. , Chalupová M. , Hurtalová L. , Tillová E. , Chalupová M.

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3

Phase Transformation And Mechanical Properties Of Ti-12.1Mo-1Fe Alloy With Nano-Sized Precipitation

72%

Lee D.-G. , Seo J. , Li C. , Lee Y.

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2015

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tom Vol. 60, iss. 2B

1393--1396

EN

Microstructural characterization and aging hardening behaviors of a new designed Ti-12.1Mo-1Fe alloy during solution treatment and aging were investigated in the present study. It is well known that when β-Ti alloys are generally under solution treatment or aging, α phases and ω phases appear or disappear dependent on heat treatment temperature and holding time. It is very necessary to understand the phase transformation phenomenon and to control the microstructure because these phases can control the drastic changes of the mechanical and physical properties of these alloys. According to the calculated [Mo]eq value and the microstructural observation, the β-transus temperature was about 780°. After the solution treatment, this alloy was composed of the β-phase and the microstructure mainly consisted of the equiaxed β grains with the average size of 25 μm. ω phases which were precipitated during aging process, played a more important role to the hardening effect than α phases. The highest hardness value of Ti-12.1Mo-1Fe alloy showed in the condition of the aging temperature of 450°. The hardening due to ω-phase precipitation can lead to a high hardness about 480 Hv but the coarse α-phase result in hardness below 300 Hv.

4

Aging kinetics and mechanical properties of copper-bearing low-carbon HSLA-100 microalloyed steel

72%

Sohrabi M. J. , Mirzadeh H. , Mehranpour M. S. , Heydarinia A. , Razi R.

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tom Vol. 19, no. 4

1409--1418

EN

The precipitation kinetics of HSLA-100 steel and the correlation between tensile and impact properties were studied. According to the modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis and based on the analysis of the time corresponding to the transformed fraction of 0.5 (t0.5), the activation energy for the precipitation of copper during aging of martensite was determined as ~111 and 105 kJ/mol, respectively. These values are much smaller than the activation energy for the diffusion of Cu in a-iron, which was related to the effect of high dislocation density of the quenched martensitic microstructure on the aging process. These results were verified based on the diffusional calculations. Based on the analysis of mechanical behavior, no reasonable correlation was found between strength of the material and the impact energy. However, the impact energy was found to be propor-tional to the UTS-YS, where the latter is an indicator of the work-hardening capability of the material. This revealed that the work-hardening capacity of the material is a much more important factor for determining the impact toughness compared to its strength.

5

Impact of the type of quench aging after hyperquenching on the mechanical strength properties of AW-7020 alloy

72%

Hajdukiewicz G.

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tom Vol. 25, No. 2

141--148

EN

The article attempts to determine the influence of selected types of the heat treatment on the strength properties of the AW-7020 alloy used in the shipbuilding industry. The text presents information on the applied types of heat treatment. There are presented the results of the static tensile test of the material after its earlier hyperquenching and aging (natural and artificial) as well as comparison to the test results of the alloy without heat treatment. To illustrate the nature of the supersaturation and aging process, a test was carried out for a series of samples in a transitional state. During the tests for all the samples were determined: elongation at rupture and reduction of area at fracture, strength limit Rm and proof stress Re0.2. The results of the tests showed that the choice of the type of aging after saturation has significant importance for the strength properties of the AW-7020 alloy. It has been shown that it is possible to significantly accelerate the achievement of higher strength properties of the tested alloy, replacing the natural aging of the material with artificial aging.

6

Effect of age hardening on corrosion resistance and hardness of CoCrMo alloys used in dental engineering

72%

Dobrzański L. , Reimann Ł. , Krawczyk C.

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tom Vol. 57, nr 1

5-12

EN

Purpose: The goal of the study is to research the effect of various time of ageing on corrosion resistance, hardness and structures of Remanium 2000+ Co-Cr-Mo alloys used in prosthodontia. Design/methodology/approach: To investigation was prepared mould, cast in 1430°C and realized the heat treatment: solutioning in 1250°C by 3 hours and then ageing in 850°C by 4, 8, 16 and 24 hours. Electrochemical corrosion examination were made in water center which simulated artificial saliva environment. The evaluation of breakdown potential was realized by recording of anodic polarization curves with use the potentiodynamic methods. Corrosion resistance test were carried out at room temperature and use of the VoltaLabŽ PGP201 system for electrochemical tests. Hardness test were obtained by use the microhardness FM ARS 9000 FUTURE TECH with load 1 kg. Structure observation was made after surface preparation: grinding, polishing and etching by light microscope LEICA MEF4A with the magnification 500x. Findings: The age hardening for Co-Cr-Mo alloys is one of the possible method which effect in forming the hardness. The highest value of hardness were obtain for specimen which was ageing with the longer time. Research alloy characterized dendritic crystals in structure for all realized heat treated process. At specimen after the longer ageing was observed the most of discontinuous precipitation and stacking faults in compare with specimen ageing by 4 hours. The age hardening doesn’t influenced much on electrochemical results and only the open circuit potential changed by decreased while increased ageing time. The values of breakdown potential and repassivation potential kept at a constant level. Practical implications: Research material is used on dentures so it’s demand that their characterized corrosion resistance and result of this work make up an information on what heat treatment parameters may be pay attention for CoCrMo alloys. Originality/value: The paper present effect of age hardening especially the ageing time, on the most important criteria of CoCrMo alloys use in dental engineering.