During solution heat treatment above the solvus, Mg 2 Si particles will be completely dissolved or reduced in size, depending on the temperature and holding time. The areas, volume fractions and size distributions of Mg 2 Si particles after different treatment temperatures and holding times were quantitatively measured in this part.
Full Answer
Why does the Mg2Si strengthen the AL?
In this paper, it is shown that the precipitation sequence in the balanced alloy is independent of the composition and the strength increases with Mg2Si level. This is due primarily to both a higher volume fraction and a refined distribution of the β″ particles.
What is the effect of solution treatment temperature on precipitation hardening?
Solution temperature has an obvious effect on precipitates formation and age-hardening behavior of Al-15%Mg2Si(-1%Cu) alloys. The increased solution temperature (from 520 °C to 550 °C) can reduce the formation activation energies of precipitates (β'' and S).
Why do we quench the specimen before age hardening it?
By rapidly quenching the specimen in water there is no time for any phase transformations to occur so that essentially, the solid solution is retained at room temperature.Jan 25, 2018
How does quenching affect microstructure?
The rapid quenching changes the crystal structure of the steel, compared with a slow cooling. Depending on the carbon content and alloying elements of the steel, it can get left with a harder, more brittle microstructure, such as martensite or bainite, when it undergoes the quench hardening process.May 9, 2019
Why quenching is done?
Quenching improves a metal's performance by rapidly cooling the heated metal, thereby altering its molecular structure and increasing its hardness. The rate of quenching may be adjusted to achieve the desired properties.Feb 20, 2018
What happens when you quench steel?
Quenching is a rapid way of bringing metal back to room temperature after heat treatment to prevent the cooling process from dramatically changing the metal's microstructure. Metalworkers do this by placing the hot metal into a liquid or sometimes forced air.Aug 9, 2019
Abstract
This study evaluates the heat treatment effects on microstructural and mechanical properties of A357 alloy. Solution treatments performed at 540 °C for 6, 8, and 10 h represent identical microstructures and show that the eutectic phase is partially dissolved into the matrix, resulting in Si particles of similar shape and size.
1. Introduction
The applications of Al-Si-Mg alloys in aerospace and automobile industry have been increasing considerably from the last two decades due to their tremendous castability, better corrosion resistance, and higher strength to weight ratio.
2. Experimental procedure
An Al ingot of commercial purity of 99.7 wt % was cut into small pieces, dried at 200 °C to take out moisture, and then melted in a graphite crucible using an electric resistance furnace at 690 °C.
4. Conclusions
This study investigated the role of various heat treatment parameters in developing the precipitation kinetics and provided a brief insight into the contribution of Mg 2 Si precipitates in determining the ductility of A357 alloy.
Data availability
The raw/processed data required to reproduce these findings are available from the corresponding author upon reasonable request.
Author contribution
As being the authors of this research paper, we declare that the work is entirely original, any raw data exiting in the article can be provided. Besides, the work has never been submitted/published in any other journal.
Acknowledgment
This work is funded by the National Key Research and Development Program of China ( 2016YFB0301000 ), Shanghai Rising-Star Program ( 15QB1402700) and National Natural Science Foundation of China ( 51671128 & 51771113 ). The authors are also thankful to Instrument Analysis Center of SJTU for providing experimental and testing facilities.
Abstract
The temperature and time dependence of the radii of Mg 2Si precipitates in 6082 Al alloy under different post-homogenization cooling rates over a wide range of 32–120,000 °C/h were investigated by scanning and transmission electron microscopy.
1. Introduction
Owing to stringent CO 2 emission norms, there is a rapidly increasing demand for electric vehicles. Extrusions of 6xxx Al-Mg-Si alloys are more widely used in the manufacture of electric vehicles owing to their lower price, excellent corrosion resistance, and superior extrudability compared to other lightweight materials [1].
2. Experimental
An ingot of direct chill casted 6082 Al alloy 178 mm in diameter was used in this study, and its chemical composition is shown in Table 1. Samples were cut from the center of the ingot and soaked at 560 °C for 8 h in a muffle furnace.
3. Results
The microstructural evolution of the 6082 alloy before (a and c) and after (b and d) homogenization heat treatment is shown in Fig. 1. The micrographs in Fig. 1 were obtained by SEM (a and b) and optical microscopy (c and d).
4. Discussions
According to Zajac et al. [13] and Reiso [15], to reduce deformation resistance, avoid incipient melting of Mg 2 Si precipitates, and improve extrusion surface quality and mechanical properties, the precipitate size, which is closely related to the post-homogenization cooling rate, should be optimized.
5. Conclusions
In this work, we studied the precipitation behavior of Mg 2Si in a 6082 alloy during the post-homogenization cooling process over a wide range of cooling rates (32–120,000 °C/h) by means of XRD, DSC, SEM, TEM, and hardness testing.
CRediT authorship contribution statement
JIAN QIN: Conceptualization, Methodology, Data curation, Writing-Original draft preparation, Formal analysis, Investigation, Writing-Reviewing and Editing. Hiromi Nagaumi: Supervision, Project administration, Funding acquisition, Writing-Reviewing and Editing. Chengbin Yu: Visualization, Investigation, Data Curation.
Abstract
The microstructure and flow stress behavior of thermomechanically processed Al–Cu/Mg 2 Si in-situ composite was studied emphasizing the evolution of primary and secondary reinforcement phases. Toward this end, the hot compression tests were conducted over the wide range of temperature (300–500 °C) and strain rate (0.001–0.1 s −1).
1. Introduction
The size and volume fraction of the present reinforcements along with the nature of matrix–reinforcement interfaces have been recognized as the main factors affecting the characteristics of the metal matrix composites (MMCs) [1].
2. Materials and methods
The experimental material was an Al–Cu/Mg 2Si in situ metal matrix composite, the chemical composition of which is shown in Table 1 .The initial microstructure of the alloy ( Fig.
4. Conclusion
The evolution of the Mg 2 Si phase (primary and secondary) in Al–Cu/Mg 2 Si in-situ composite was studied under the various thermomechanical conditions. The mechanical fragmentation of the primary Mg 2 Si phase is characterized as one of the main strain accommodation mechanism at low temperature regime.