Zn/Cu regulated critical strain and serrated flow behavior in Al–Mg alloys

The serrated flow phenomena in Al-Mg alloys with and without Zn were investigated after aging on several conditions, focusing on the role of precipitates. Al-6mass%Mg-0~3mass%Zn alloys were solution treated at 753~803K, quenched, and then aged at room temperature. Further artificial aging at 323~573K for 86.4ks was performed for some of them after natural aging for 2.6Ms. The serrated flow behavior was evaluated by tensile test. Microstructure was characterized by differential scanning calorimetry, transmission electron microscopy, atom probe tomography, and positron annihilation lifetime spectroscopy. The increase in the amount of Zn addition and the natural aging time lead to a delayed onset of serrated flow. The artificial aging at higher temperatures after natural aging, on the other hand, decreases the onset strain. A large number of small coherent Zn-Mg clusters are formed during natural aging in the Al-Mg-Zn alloys, which are transformed to the larger incoherent meta-stable precipitates during subsequent artificial aging. These results suggest that the mechanism of interfering with serrated flow is related to the vacancy trapping effect, which is enhanced by the coherent clusters.

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On the strain rate dependence of the critical strain for plastic instabilities in Al-Mg alloys

Scripta Materialia ◽

10.1016/j.scriptamat.2016.11.037 ◽

2017 ◽

Vol 130 ◽

pp. 252-255 ◽

Cited By ~ 13

Author(s):

N. Chibane ◽

H. Ait-Amokhtar ◽

C. Fressengeas

Keyword(s):

Strain Rate ◽

Critical Strain ◽

Rate Dependence ◽

Mg Alloys ◽

Strain Rate Dependence ◽

Al Mg Alloys

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Serrated Flow and Enhanced Ductility in Coarse-Grained Al-Mg Alloys

Metallurgical and Materials Transactions A ◽

10.1007/s11661-010-0506-x ◽

2010 ◽

Vol 42 (4) ◽

pp. 1028-1037 ◽

Cited By ~ 3

Author(s):

Ehab Samuel ◽

John J. Jonas ◽

Fawzy H. Samuel

Keyword(s):

Mg Alloys ◽

Coarse Grained ◽

Serrated Flow ◽

Al Mg Alloys

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Solute concentration dependence of strength and plastic instabilities in Al-Mg alloys

Journal of Materials Research ◽

10.1557/jmr.2005.0040 ◽

2005 ◽

Vol 20 (2) ◽

pp. 331-337 ◽

Cited By ~ 5

Author(s):

Gy. Horváth ◽

N.Q. Chinh ◽

J. Lendvai

Keyword(s):

Dislocation Line ◽

Solute Concentration ◽

Mg Alloys ◽

Dynamic Strain ◽

Solute Content ◽

Serrated Flow ◽

Indentation Tests ◽

Power Law Function ◽

Chatelier Effect ◽

Al Mg Alloys

Characteristics of the dynamic strain aging (DSA) in the Portevin-Le Chatelier effect are experimentally investigated by dynamic indentation tests and numerically analyzed by using literature models. Experimental results obtained on Al–Mg alloys show that the occurrence and development of the plastic instabilities—serrated indentation—depend strongly on the solute content. During dynamic microindentation tests the amplitude of microhardness drops—similarly to the global hardness—and is changing as a power law function of Mg solute content with an exponent of 2/3. It has been shown that the term describing the effect of DSA in serrated flow is not proportional but rather a power expression of the local solute concentration, Cs, on the dislocation line with the exponent of 1/2. Together with this, the kinetics of solute segregation during DSA is controlled by the pipe diffusion.

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Ageing effect on serrated flow in Al–Mg alloys

Materials Science and Engineering A ◽

10.1016/s0921-5093(02)00769-4 ◽

2003 ◽

Vol 349 (1-2) ◽

pp. 272-278 ◽

Cited By ~ 18

Author(s):

Baohui Tian

Keyword(s):

Mg Alloys ◽

Ageing Effect ◽

Serrated Flow ◽

Al Mg Alloys

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Effect of Auto-Tuning on Serrated Flow Behavior

Metals ◽

10.3390/met9080845 ◽

2019 ◽

Vol 9 (8) ◽

pp. 845 ◽

Cited By ~ 1

Author(s):

S.M.A.K. Mohammed ◽

D.L. Chen

Keyword(s):

Mild Steel ◽

Mechanical Response ◽

Flow Behavior ◽

Adaptive Controller ◽

Tensile Tests ◽

Hydraulic Testing ◽

Al Alloys ◽

Mg Alloys ◽

Serrated Flow ◽

Auto Tuning

The mechanical response of a servo-hydraulic testing system is affected by the stiffness of test specimens. An adaptive controller helps in auto-tuning the system by setting the optimal proportional-integral-derivative values for the subsequent test as the stiffness changes. This paper presents the effect of auto-tuning of various channels on the flow response of several commercial Al and Mg alloys and a mild steel. Strain-controlled monotonic tensile tests were performed at a given strain rate of 1 × 10−4 s−1 after auto-tuning of position, load, and strain channels in different combinations. Serrated flow or Portevin–Le Chatelier effect was observed in the Al alloys after auto-tuning of either position channel only or position and load channels. However, the serrations of Al alloys were shielded after further auto-tuning of strain channel. The stress-strain curves of Mg alloys and mild steel were observed to be basically free of serrations under any combinations of auto-tuning, which confirms that the serrated flow is a property of specific materials rather than a machine system noise.

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