scholarly journals The Correlation of Microstructure and Mechanical Properties of In-Situ Al-Mg2Si Cast Composite Processed by Equal Channel Angular Pressing

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1553 ◽  
Author(s):  
Mahdi Chegini ◽  
Mohammad Shaeri ◽  
Reza Taghiabadi ◽  
Sajjad Chegini ◽  
Faramarz Djavanroodi

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity.

2012 ◽  
Vol 560-561 ◽  
pp. 344-348 ◽  
Author(s):  
Wei Wei ◽  
Kun Xia Wei ◽  
Igor V. Alexandrov ◽  
Qing Bo Du ◽  
Jing Hu

The effect of aging treatment on mechanical properties and electrical conductivity of Cu-5.7%Cr in situ composite produced by equal channel angular pressing (ECAP) was investigated here. The rotation and spreading of Cr particles was observed in Cu-5.7%Cr alloy during the ECAP, resulting in long thin in situ filaments. The equiaxed grains of the Cu phase with an average size of 200 nm were developed after eight passes of ECAP. When aging at 400~450 °C for 1 h, Cu-5.7%Cr composite after ECAP shows the maximum microhardness, and the electrical conductivity is larger than 70% of IACS. At 400 °C, the peak aging time appears for 0.5~2 h, dependent on the pre-strain for all ECAP samples. With the increase of ECAP passes, the enhancement of tensile strength due to the aging treatment declines, and even shows negative after eight passes of ECAP. The combination of ECAP and aging treatment would be a promising process to balance mechanical properties and electrical conductivity of Cu-5.7%Cr composite.


2013 ◽  
Vol 747-748 ◽  
pp. 289-294
Author(s):  
Yi Zhang ◽  
Fu Yin Han ◽  
Yong Sheng Wang ◽  
Wei Liang ◽  
Ping Wang ◽  
...  

The Mg-6Zn-2Si alloy was processed by equal channel angular pressing (ECAP) for 4 passes and 8 passes at 573K, and the microstructure and mechanical properties of the alloy before and after ECAP were studied. The results show that Chinese script type interphase of Mg2Si was crushed into dispersed particles, and significant grain refinement was also introduced to the matrix phase (α-Mg) and Mg51Zn20 phase after 4 passes of ECAP. The yield strength was increased by 180%, elongation by 140% and tensile strength by 75%. The microstructure and mechanical properties remained reasonably constant between 4 and 8 passes of ECAP. The mechanism of improvement on microstructure and mechanical properties of the experimental alloy by subjecting ECAP was also investigated.


2013 ◽  
Vol 58 (2) ◽  
pp. 481-487 ◽  
Author(s):  
K. Bryła ◽  
J. Dutkiewicz ◽  
L.L. Rokhlin ◽  
L. Litynska-Dobrzynska ◽  
K. Mroczka ◽  
...  

The influence of ageing and Equal Channel Angular Pressing (ECAP) on the microstructure and mechanical properties of Mg-2.5%Tb-0.78%Sm alloy has been examined. The microhardness changes during ageing at 200ºC show a slight increase. The aged microstructure at maximum hardness contains Mg12(Tb,Sm) - metastable β’ phase of size about 2-10 nm as dispersed precipitates. The orientation relationship between β’ phase and the matrix was found as follows:(0001)Mg || (1¯10)β′, [21¯10]Mg || [116]β′. The ECAP passes were performed by two procedures: “I” - four passes at 350ºC; “II” - one pass at 370ºC, second pass at 340ºC and third pass at 310ºC. The grain size was reduced about 200 times as a results of ECAP process according “I” and “II” procedure. The grain refinement by ECAP improves significantly the compression yield strength and hardness. The Hall-Petch relationship was confirmed basing on microhardness measurements and the grain size after ECAP. The Mg24(Tb,Sm)5 and Mg41(Sm,Tb)5 particles smaller than 150 nm are located mainly at grain and subgrain boundaries and they prevent grain growth during ECAP processing. The microstructure evolution during ECAP can be described as dynamic recovery and continuous and discontinuous dynamic recrystallization.


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