Addressing the strength-ductility trade-off in a cast Al-Li-Cu alloy——synergistic effect of Sc-alloying and optimized artificial ageing scheme

This study reports on the effect of interrupted quenching on the microstructure and mechanical properties of plates made of the AlZnMg(Cu) alloy AA7050. Rapid cooling from the solution heat treatment temperature is interrupted at temperatures between 100 and 200 °C and continued with a very slow further cooling to room temperature. The final material’s condition is achieved without or with subsequent artificial ageing. The results show that an improvement in the strength–toughness trade-off can be obtained by using this method. Interrupted quenching at 125 °C with peak artificial ageing leads to a yield strength increase of 27 MPa (538 MPa to 565 MPa) compared to the reference material at the same fracture toughness level. A further special case is the complete omission of an artificial ageing treatment with interrupted quenching at 200 °C. This heat treatment exhibits an 20% increase in fracture toughness (35 to 42 MPa m−1/2) while retaining a sufficient yield strength of 512 MPa for industrial applications. A detailed characterization of the relevant microstructural parameters like present phases, phase distribution and precipitate-free zones is performed using transmission electron microscopy and atom probe tomography.

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Synergistic Effect of Cu Single Atoms and Au–Cu Alloy Nanoparticles on TiO2 for Efficient CO2 Photoreduction

ACS Nano ◽

10.1021/acsnano.1c03961 ◽

2021 ◽

Author(s):

Yangyang Yu ◽

Xing’an Dong ◽

Peng Chen ◽

Qin Geng ◽

Hong Wang ◽

...

Keyword(s):

Synergistic Effect ◽

Alloy Nanoparticles ◽

Co2 Photoreduction ◽

Single Atoms ◽

Cu Alloy

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Effect of Second Phases on Tensile Property in Artificial Ageing and RRA Process of Super-High Strength Aluminum Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.855 ◽

2007 ◽

Vol 546-549 ◽

pp. 855-862

Author(s):

Ai Lin Ning ◽

Zhi Yi Liu ◽

Chun Feng ◽

Su Min Zeng

Keyword(s):

Tensile Strength ◽

Aluminum Alloy ◽

Tensile Test ◽

High Strength ◽

Peak Strength ◽

Artificial Ageing ◽

High Strength Aluminum Alloy ◽

Cu Alloy ◽

Second Phases ◽

Strengthening Particles

The evolution of second phases and its effect on tensile mechanical property in artificial ageing and RRA process of super-high strength aluminum alloy is investigated.The result of tensile test shows that the samples of Al-Zn-Mg-Cu-Ag alloy aged at lower temperature(100°C) not only have higher tensile strength up to 753Mpa but also relatively higher tensile elongation above 9% than normal temperature(120°C) in artificial ageing. The sample of Al-Zn-Mg-Cu alloy has the highest tension strength upto 788Mpa when aged at 100°C for 48 hours in single step of artificial ageing. Further more in RRA process samples of Al-Zn-Mg-Cu alloy preaged at 100°C for 24 hours retrogressed at 200°C for 7min and reaged at 100°Cfor 24 hours present the best tensile strength of 795Mpa than others. The tensile strength of Al-Zn-Mg-Cu alloy after RRA treated decreases with prolonging of retrogression time and reageing time starting from 7mins and 24 houres respectively. SEM observation shows that crack of the samples in tensile test is created at large particles in the fracture while there are more particles of undissolved phase in Al-Zn-Mg-Cu alloy containing Ag. TEM observation shows that the dominant strengthening particle corresponding to the peak strength of Al-Zn-Mg-Cu alloy containing Ag when aged at 120°C for 8 hours is η’ phase while dominant strengthening particle is G.P zone when aged at 100°C for 80 hours. However, η’ phase as the dominant strengthening particles corresponds to the peak strength of Al-Zn-Mg-Cu alloy without content of Ag when aged at 100°C for 48hours. TEM observation also shows that G.P zone as strengthening particle is dominant in the samples of Al-Zn-Mg-Cu alloy reaged at 100°C for 24 hours, and strengthening particles is coarsened when the sample is retrogressed at 200°C and reaged for a longer time. It is suggested that whether at the presence of coarse particles of undissolved phases or when G.P zone and η’ particle grow up in the retrogression ,sample needs deformable G.P zone instead of undeformable η’ in subsequent artificial ageing and reageing as dominant strengthening particle, in order to present a larger freedom spacing for dislocation to slip and let the sample not to behave too brittle to display high resistance to imposed plastic deformation or high tensile strength.

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Ageing Precipitation and Strengthening Behavior of the Spray Formed Al-Zn-Mg-Cu Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.535-537.903 ◽

2012 ◽

Vol 535-537 ◽

pp. 903-908

Author(s):

Hong Wei Liu ◽

Feng Wang ◽

Bai Qing Xiong ◽

Yon Gan Zhang ◽

Zhi Hui Li ◽

...

Keyword(s):

Ageing Time ◽

Spray Forming ◽

Artificial Ageing ◽

Forming Process ◽

Scanning Calorimetry ◽

Cu Alloy ◽

Transmission Electron ◽

Peak Aging ◽

Time Strength ◽

Age Strengthening

In this study, the Al-Zn-Mg-Cu alloy was prepared by spray forming process. The ageing precipitation and strengthening behavior of the spray formed Al-Zn-Mg-Cu alloy were studied by microhardness tests, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) .The results show that the main strengthening precipitates of the spray formed Al-Zn-Mg-Cu alloy are GPI (solute-rich clusters), GPII (vacancy-rich clusters) under peak aging condition. The effect of the microstructure on ageing hardness is controlled by the size and amount of the existing precipitates, and therefore depends critically on the ageing temperature and ageing time. Strength of this alloy is influenced significantly during natural ageing at room temperature, which is related to the dominant formation of GPI. During the initial stage of artificial ageing at 120°C, strong age-strengthening response is due to the formation of GP zones (both GPI and GPII ) .During later stages of artificial ageing , GPII precipitation is accelerated significantly but GPI is not affected clearly.

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Experimental Investigation Of Modified Heat Treatment Of AK64-Type Al-Si-Cu Sand Cast Alloy

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0391 ◽

2015 ◽

Vol 60 (3) ◽

pp. 2397-2402 ◽

Cited By ~ 1

Author(s):

L.H. Cupido ◽

P.L. Żak ◽

N. Mahomed ◽

J. Lelito ◽

G. Piwowarski ◽

...

Keyword(s):

Heat Treatment ◽

Experimental Investigation ◽

Cast Alloy ◽

Eutectic Reaction ◽

Artificial Ageing ◽

Sand Cast ◽

Cu Alloy ◽

Heat Treated ◽

Dendrite Network ◽

Higher Temperature

Abstract An experimental investigation was conducted to observe and analyze the microstructural evolution of phases present in the AK64 Al-Si-Cu alloy subjected to a modified T6 heat treatment (HT). The AK64 alloy1 is the Polish alternative of the A319.0 ASM standard aluminium alloy. The modified T6 HT schedule with a higher temperature and shorter duration was applied in the solutioning process and lower quenching and higher artificial ageing temperature than the prescribed by the ASM standard were used. The cooling curves registered during the liberating of overheating and solidifying processes give important information on nucleation temperatures for the Al dendrite network, Al-Si eutectic reaction and precipitation of Cu-rich phases. Comparison of the as-cast and heat treated microstructures revealed predicted microstructural changes and also partial fragmentation of the Fe-rich phases was observed after the application of the modified HT programme.

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Precipitate Behavior and Microstructure Characterization of An Al-Zn-Mg-Cu Alloy Prepared by Spray Forming Process

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.481 ◽

2010 ◽

Vol 638-642 ◽

pp. 481-486

Author(s):

Bao Hong Zhu ◽

Bai Qing Xiong ◽

Yon Gan Zhang ◽

Udo Fritsching ◽

Ji Shan Zhang ◽

...

Keyword(s):

Early Stage ◽

Ageing Time ◽

Spray Forming ◽

Artificial Ageing ◽

Strengthening Phase ◽

Forming Process ◽

Ageing Treatment ◽

Cu Alloy ◽

The Matrix ◽

Coherent Relationship

A high Zn content Al-Zn-Mg-Cu alloy was prepared by spray forming process and the precipitate behavior and microstructure of the extruded alloy were also investigated. The precipitate sequence of the spray-formed alloy could be described as “α-solid solution → GPI zone → GPII zone (also called Metastable ′ )→ Stable  (MgZn2)” during artificial ageing treatment. In the early stage of artificial ageing treatment, the GPI zone was the main strengthening phase and kept coherent relationship with the matrix. With the increasing of ageing time, ′ phase dominate strengthening phase and kept semi-coherent relationship with the matrix. With the further increasing of ageing time,  phase took the place of ′ phase, and dominated the strengthening phase in the alloy. The grain size of the spray deposit is finer than that of cast alloys. The ultimate tensile strength of the alloy is over 810MPa in peak ageing condition.

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