Hall-Petch Relation and Strengthening Mechanisms in Al-Zn-Mg-Cu Alloy Polycrystals.

長門, 小野; 仁, 合谷; 精, 三浦

doi:10.1299/kikaia.68.1136

Cited by 5 publications

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“…(2) is not known for 7475 aluminum alloys. Therefore, if we assume the À value of 232 mJÁm À2 which was adopted in the analysis for the experimental results of this alloy polycrystals by Ono et al, 7) Á( is estimated to be 62, 124 and 161 MPa for the specimens of S 1 , S 2 and S 3 , respectively. It is noteworthy that the À value of 200$230 mJÁm À2 was reported for the case of cobalt precipitates in Cu-Co alloys.…”

Section: Theory Of Precipitation and The Present Resultsmentioning

confidence: 99%

Hardness and Stress-Strain Curves of Al-Zn-Mg-Cu Alloy Single Crystals

et al. 2008

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The present paper describes the variations of the mechanical properties of Al-Zn-Mg-Cu alloy single crystals with various aging times. The cylindrical single crystals of 7475 aluminum alloys were produced at 1033 K by the Bridgeman method, where the composition of initial material and the shape of carbon mold were modified for the growth of quaternary crystals. The specimens proper for tensile and hardness testing were obtained from the single crystal rod homogenized at 823 K for 900 ks using spark-cutting method. Subsequently, they were aged at 393 K for 3.6, 86.4, 900 and 2880 ks after quenching in ice water from 773 K. In the stress-strain curves of the alloy single crystals, the increase of yield stress and the decrease of elongation with an increase of aging time are seen together with a decrease in the rate of work hardening. Moreover, some serrations occur especially in the final plastic stage on the curves. Hardness of the alloy single crystals agrees with those of polycrystals due to the occurrence of multiple slips during loading. However, the alloy single crystals exhibit a marked decrease of yield strength in comparison with the polycrystals, which results from a single glide occurring in the single crystals. If we compare the increase of critical resolved shear stress (CRSS) derived from two kinds of theories of precipitation with the experimental value, both of them are roughly in agreement except for the specimen aged for 3.6 ks. The obtained results indicate that the maximum strength of Al-Zn-Mg-Cu alloy single crystals is achieved in the transitional process between the mechanism of particle cutting and the Orowan mechanism.

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Section: Theory Of Precipitation and The Present Resultsmentioning

confidence: 99%

Hardness and Stress-Strain Curves of Al-Zn-Mg-Cu Alloy Single Crystals

et al. 2008

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“…Therefore, the degree of age hardening of Semi-A2024 is larger than that of Melt-A2024. In the age hardening-type aluminum alloys, the precipitation effect will contribute more to the strength of cell walls than the effect of grain boundary strengthening [19]. Therefore, the hardness of cell walls of the Semi-A2024 alloy is larger than that of Melt-A2024.…”

Section: The Effect Of the Difference In Pore Morphology And The Cellmentioning

confidence: 99%

Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route

Kubo

Osaka

Saito

et al. 2019

Metals

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A2024 alloy foams were fabricated by two methods. In the first method, the melt was thickened by Mg, which acts as an alloying element (melt route). In the second method, the melt was thickened by using primary crystals at a semi-solid temperature with a solid fraction of 20% (semi-solid route). A2024 alloy foams fabricated through the semi-solid route had coarse and uneven pores. This led to slightly brittle fracture of the foams, which resulted in larger energy absorption efficiency than that of the foams fabricated through the melt route. Moreover, A2024 alloy foams fabricated through the semi-solid route had a coarser grain size because of the coarse primary crystals. However, by preventing the decrease in the alloying element Mg, the θ/θ’ phase was suppressed. Additionally, by preventing the precipitation of the S′ phase, the amount of Guinier-Preston-Bagaryatsky (GPB) zone increased. This resulted in a larger plateau stress.

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“…Relation between the flow stress and the inverse square root of the average grain size: (a) as quenched specimen, (b) aged specimen for 86.4 ks. Two kinds of dashed lines are data in the 0.1 proof stress of 7475 alloys4) and as quenched pure aluminum6) , respectively.第 4 号 Al Zn Mg Cu 合金多結晶におけるすべりのその場観察に基づく Hall Petch 関係の評価少数現れ，明瞭な多重すべりの様相を呈する．一方時効試料では，溶体化試料の場合に比べて塑性変形が進行した e P ＝ 0.19, s E ＝378 MPa の段階で Fig. 2 と同様な形態の一次すべり帯が粗大結晶粒内に現れ始めるが，e P ＝0.99, s E ＝ 413 MPa までの変形範囲において二次すべり帯は確認できない． 3.2 すべり帯の出現開始応力の粒径依存性Fig.…”

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Evaluation of Hall-Petch Relation Based on In-Situ Observation of Slip Bands in Al-Zn-Mg-Cu Alloy Polycrystals

Ono

Gouya

Miura

2003

J. Japan Inst. Metals and Materials

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It is widely recognized that precipitation hardening brings considerable improvements of mechanical properties in 7000 type Al Zn Mg Cu polycrystalline alloys. In order to make clear the effects of grain boundaries on yielding, we have studied the relationship between flow stress and slipped grain size for 7475 alloys by using an in situ observation of slip bands. Two kinds of specimens were prepared; one was a solution treated at 753 K for 1.1 ks, and the other one was a solution similarly treated and T6 aged at 393 K for 86.4 ks. The in situ observations in the surface grains of both specimens were continuously performed in deformation ranges from 0 to about 1 plastic strain. The Hall Petch relation was confirmed between the flow stress and the average slipped grain size in the vicinity of 0.2 proof stress, although each specimen consisted of heterogeneous grains of different sizes. The slope k y in the relation was almost independent of aging, and the increase of frictional stress s 0 with aging was remarkable. The shear stress for releasing edge dislocation locking derived from the values of k y and s 0 in an as quenched specimen was twice as great as the CRSS of 7475 alloy single crystals. Comparing the values of s 0 in as quenched and aged specimens, the increase of frictional stress with T6 aging was in agreement with 270 MPa estimated for 0.5 proof stresses of single crystal alloys.

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Hall-Petch Relation and Strengthening Mechanisms in Al-Zn-Mg-Cu Alloy Polycrystals.

Cited by 5 publications

References 0 publications

Hardness and Stress-Strain Curves of Al-Zn-Mg-Cu Alloy Single Crystals

Hardness and Stress-Strain Curves of Al-Zn-Mg-Cu Alloy Single Crystals

Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route

Evaluation of Hall-Petch Relation Based on In-Situ Observation of Slip Bands in Al-Zn-Mg-Cu Alloy Polycrystals

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