| 1. |
- Ceschini, Lorella, et al.
(författare)
-
Al-Si-Cu alloys for high pressure die casting : Influence of Fe, Mn, and Cr on room temperaturemechanical properties
- 2016
-
Ingår i: La Metallurgia Italiana. - Milano : Associazione Italiana di Metallurgia. - 0026-0843. ; :6, s. 77-80
-
Tidskriftsartikel (refereegranskat)abstract
- Al-Si-Cu alloys with high Fe content are widely employed in high pressure die casting (HPDC). Even if Feis usually considered an impurity in secondary aluminum alloys, leading to the formation of harmfulintermetallic compounds, it helps in mitigating or eliminating the problem of die soldering. As a result,secondary Al alloys with Fe content of about 1 wt% are commonly employed for the production of HPDCcastings. Aiming to change the morphology of harmful Fe-bearing phases towards less detrimentalmorphologies, proper alloying elements may be added to the alloys. Mn and Cr (both present in thealuminum scrap), as instance, are reported to prevent from the formation of the acicular β-Al5FeSi phase,leading to the formation of more compact and polygonal intermetallics. Such phases are usually referredto as “sludge” particles. The influence of sludge particles on mechanical properties of Al -Si-Cu castings isstill under investigation. The present work aims at evaluating the effect of impurities (Fe, Mn and Cr)typically present in secondary Al alloys on the microstructure and mechanical properties of the A380 (Al -Si-Cu) alloy. Samples with different Fe, Mn and Cr content were produced and processed through adirectional solidification equipment to obtain specimens with controlled SDAS (~10 μm). Hardness androtating bending fatigue tests were carried out at room temperature. Mechanical properties of the alloyswere then related to the microstructure, analyzed by optical and scanning electron microscopy.
|
|
| 2. |
- Ceschini, Lorella, et al.
(författare)
-
Aluminum and Magnesium Metal Matrix Nanocomposites
- 2017
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- The book looks into the recent advances in the ex-situ production routes and properties of aluminum and magnesium based metal matrix nanocomposites (MMNCs), produced either by liquid or semi-solid state methods. It comprehensively summarizes work done in the last 10 years including the mechanical properties of different matrix/nanoreinforcement systems. The book also addresses future research direction, steps taken and missing developments to achieve the full industrial exploitation of such composites. The content of the book appeals to researchers and industrial practitioners in the area of materials development for metal matrix nanocomposites and its applications.
|
|
| 3. |
- Ceschini, Lorella, et al.
(författare)
-
Effect of Cu addition on overaging behaviour, room and high temperature tensile and fatigue properties of A357 alloy
- 2020
-
Ingår i: Transactions of Nonferrous Metals Society of China. - : Elsevier. - 1003-6326 .- 2210-3384. ; 30:11, s. 2861-2878
-
Tidskriftsartikel (refereegranskat)abstract
- The aims of the present work are to evaluate the overaging behaviour of the investigated Cu-enriched alloy and to assess its mechanical behaviour, in terms of the tensile and fatigue strength, at room temperature and at 200 °C, and to correlate the mechanical performance with its microstructure, in particular with the secondary dendrite arm spacing (SDAS). The mechanical tests carried out on the overaged alloy at 200 °C indicate that the addition of about 1.3 wt.% Cu to the A357 alloy enables to maintain ultimate tensile strength and yield strength values close to 210 and 200 MPa, respectively, and fatigue strength at about 100 MPa. Compared to the quaternary (Al−Si−Cu−Mg) alloy C355, the A357−Cu alloy has greater mechanical properties at room temperature and comparable mechanical behaviour in the overaged condition at 200 °C. The microstructural analyses highlight that SDAS affects the mechanical behaviour of the peak-aged A357−Cu alloy at room temperature, while its influence is negligible on the tensile and fatigue properties of the overaged alloy at 200 °C.
|
|
| 4. |
- Ceschini, Lorella, et al.
(författare)
-
Effect of Microstructure and Overaging on the Tensile Behavior at Room and Elevated Temperature of C355-T6 Cast Aluminum Alloy
- 2015
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 83, s. 626-634
-
Tidskriftsartikel (refereegranskat)abstract
- The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.
|
|
| 5. |
|
|
| 6. |
- Ceschini, Lorella, et al.
(författare)
-
Microstructural and Mechanical Properties Characterization of Heat Treated and Overaged Cast A354 Alloy with Various SDAS at Room and Elevated Temperature
- 2015
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 648, s. 340-349
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to carry out a microstructural and mechanical characterization of the A354 (Al–Si–Cu–Mg) cast aluminum alloy. The effect of microstructure on the tensile behavior was evaluated by testing samples with different Secondary Dendrite Arm Spacing, (SDAS) values (20–25 μm and 50–70 μm for fine and coarse microstructure, respectively), which were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated both at room and elevated temperature (200 °C), in the heat treated and overaged (exposure at 210 °C for 41 h, after heat treatment) conditions. Optical, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) were used for microstructural investigations.Experimental data confirmed the significant role of microstructural coarseness on the tensile behavior of A354 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Moreover, solidification rate influenced other microstructural features, such as the eutectic silicon morphology as well as the size of the intermetallic phases, which in turn also influenced elongation to failure. Coarsening of the strengthening precipitates was induced by overaging, as observed by STEM analyses, thus leading to a strong reduction of the tensile strength of the alloy, regardless of SDAS. Tensile properties of the alloy sensibly decrease at elevated temperature (200 °C) in all the investigated heat treatment conditions.
|
|
| 7. |
- Ceschini, Lorella, et al.
(författare)
-
The influence of cooling rate on microstructure, tensile and fatigue behavior of heat treated Al-Si-Cu-Mg alloys
- 2017
-
Ingår i: Liquid metals and alloys. - : Trans Tech Publications. - 9783038356400 - 9783035701210 ; , s. 81-92
-
Bokkapitel (refereegranskat)abstract
- Al-Si-Mg alloys are commonly employed for the production of automotive castings. In view of the recent stringent emissions standards and consequent engine downsizing, these components must withstand higher temperatures and stresses than in the past. In this regard, the heat treatable quaternary Al-Si-Cu-Mg alloys gained particular interest in recent years, due to their superior mechanical properties and higher thermal stability. The present research activity was addressed to evaluate the influence of cooling rate on microstructure and consequently on room temperature tensile and fatigue behaviour of the A354 and C355 alloys. Samples for mechanical tests were produced under controlled cooling rates, in order to induce different secondary dendrite arm spacing (SDAS) values, classified as fine (20-25μm) and coarse (50-70μm). The experimental results showed that the cooling rate strongly influences the type, size and morphology of intermetallic particles. The presence of coarse intermetallic phases, mostly Fe-based, observed in coarse SDAS specimens, was reported to strongly affect ultimate tensile strength (UTS), elongation to failure and fatigue strength of both the investigated alloys. A correlation between UTS and fatigue resistance was found, independent of microstructural coarseness.
|
|
| 8. |
- Zamani, Mohammadreza, 1985-, et al.
(författare)
-
Optimisation of heat treatment of Al–Cu–(Mg–Ag) cast alloys
- 2020
-
Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 139, s. 3427-3440
-
Tidskriftsartikel (refereegranskat)abstract
- The optimisation of heat treatment parameters for Al–Cu–(Mg–Ag) cast alloys (2xxx) having different microstructural scales was investigated. Thermo-Calc software was used to design optimal alloy compositions. Differential scanning calorimetry (DSC), scanning electron microscopy and wavelength-dispersive spectroscopy technique were employed to determine proper solution heat treatment temperature and homogenisation time as well as incidence of incipient melting. Proper artificial ageing temperature for each alloy was identified using DSC analysis and hardness measurement. Microstructural scale had a pronounced influence on time and temperature required for complete dissolution of Al2Cu and homogenisation of Cu solute atoms in the α-Al matrix. Refined microstructure required only one-step solution treatment and relatively short solution treatment of 10 h to achieve dissolution and homogenisation, while coarser microstructures desired longer time. Addition of Mg to Al–Cu alloys promoted the formation of phases having a rather low melting temperature which demands multi-step solution treatment. Presence of Ag decreases the melting temperature of intermetallics (beside Al2Cu) and improvement in age-hardening response. Peak-aged temperature is primarily affected by the chemical composition rather than the microstructural scale.
|
|
