scholarly journals The Effect of Elastic Strain and Small Plastic Deformation on Tensile Strength of a Lean Al–Mg–Si Alloy

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1276
Author(s):  
Eva Anne Mørtsell ◽  
Ida Westermann ◽  
Calin Daniel Marioara ◽  
Ketill Olav Pedersen ◽  
Sigmund Jarle Andersen ◽  
...  

Al–Mg–Si alloys are usually formed into their final shape by rolling or extrusion. After extrusion, the aluminium profiles are usually straightened, causing the material to be subjected to a small plastic deformation. This study demonstrates the positive effect on strength that can be obtained from such small deformation levels or from only elastically straining the material. Elastic straining of a lean Al–Mg–Si alloy, when performed immediately after solution heat treatment, enhances the material yield strength after artificial ageing to T6. Transmission electron microscopy shows that this effect can be attributed to a higher number density and finer dispersion of the age-hardening precipitate needles. Furthermore, introducing a small plastic deformation of 1% after solution heat treatment results in a comparable strength increase to elastically straining the material. In this case, however, the strength increase is due to the increased dislocation density, which compensates for a lower density of precipitate needles. Finally, by combining plastic deformation with a succeeding elastic strain, we demonstrate how elastic strain can cause an on-set of dislocation cell formation in this material.


2021 ◽  
Vol 1016 ◽  
pp. 125-131
Author(s):  
Masahiro Goto ◽  
T. Yamamoto ◽  
S.Z. Han ◽  
J. Kitamura ◽  
J.H. Ahn ◽  
...  

On the thermomechanical treatments of Cu-Ni-Si alloy, cold-rolling (CR) before solution heat treatment (SHT) is commonly conducted to eliminate defects in a casting slab. In addition, a rolling is applied to reduce/adjust the thickness of casting slab before SHT. In a heavily deformed microstructure by CR, on the other hand, grain growth during a heating in SHT is likely to occur as the result of recrystallization. In general, tensile strength and fatigue strength tend to decrease with an increase in the grain size. However, the effect of difference in grain sizes produced by with and without CR before SHT on the fatigue strength is unclear. In the present study, fatigue tests of Cu-6Ni-Si alloy smooth specimens with a grain fabricated through different thermomechanical processes were conducted. The fatigue behavior of Cu-Ni-Si alloy was discussed.





2011 ◽  
Vol 399-401 ◽  
pp. 17-20
Author(s):  
Wen Bin Yu ◽  
Zhi Qian Chen ◽  
Mang Zhang ◽  
Zhou Yu

The precipitation hardening response of as-cast Mg-8Yb-0.5Zr magnesium alloy was investigated in the present work. The microstructure evolution of the alloy illustrated that Mg2Yb intermetallic phase was dissolved by solution heat treatment at 520°C for 12 hours. An apparent precipitation hardening response in Mg-8Yb-0.5Zr was discovered after artificial aging at 150°C, with maximum hardness increment of about 80 percent at the peak condition. It was found that the precipitates of the alloy were in the shape of two conjoined cosh and globe about 50 nm, and precipitated preferentially on grain boundaries and dislocations.



2007 ◽  
Vol 353-358 ◽  
pp. 50-53
Author(s):  
Jian Qui Zhou ◽  
Yuan Ling Li

In order to understand the grain size and porosity dependent mechanical behavior of porous, multi-phase nanocrystalline ceramics, each phase is treated as a mixture of grain interior and grain boundary, and pores are taken as a single phase. In conjunction with the secant-modulus approach and iso-strain assumption, Budiansky’s self-consistent method is extended to build a constitutive model for nanocrystalline ceramics with small plastic deformation. Based on the developed model, the predicted yield strength (σ0.2) values of porous, multi-phase nanocrystalline ceramics with different grain size and porosity are compared with experimental data in the literature, the comparison shows that the predictions are in good agreement with the published data. This suggests that the developed model is capable of describing the grain size and porosity dependent mechanical behaviors of nanocrystalline ceramics with small plastic deformation.



2013 ◽  
Vol 690-693 ◽  
pp. 44-48
Author(s):  
Feng Wang ◽  
Zhi Wang ◽  
Zheng Liu ◽  
Ping Li Mao

In this paper, developed a non-aluminum die casting magnesium alloys were studied based on Mg-xGd-Y-Zr(x=6, 8, 12 wt.%)alloys in cold chamber press. The microstructures and mechanical properties of die casting GWK alloys have been investigated using OM, SEM, XRD, EDS and mechanical property test. The experimental results show that with increasing Gd content of Mg-xGd-Y-Zr alloys, the tensile strength increase, but elongation decrease. In particular, die casting GWK alloys after short-term and low-temperature solid solution treatment (T4) have a small variation in grain size and more uniform microstructures, and the second phases distribute at the grain boundaries in form of discontinuous rod shape or granule shape, which result in an obvious improvement in tensile mechanical properties of alloys. The Mg-12Gd-3Y-0.5Zr die casting alloy exhibit maximum tensile strength after solution heat treatment, and the value is 269MPa at room temperature. The effect of solution heat treatment on die casting Mg-xGd-Y-Zr alloys was also discussed.





Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2554 ◽  
Author(s):  
Thomas M. Kremmer ◽  
Phillip Dumitraschkewitz ◽  
Daniel Pöschmann ◽  
Thomas Ebner ◽  
Peter J. Uggowitzer ◽  
...  

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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