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Rasouli, D., Kermanpur, A., Ghassemali, E. & Najafizadeh, A. (2019). On the reversion and recrystallization of austenite in the interstitially alloyed Ni-free nano/ultrafine grained austenitic stainless steels. Metals and Materials International, 25(4), 846-859
Open this publication in new window or tab >>On the reversion and recrystallization of austenite in the interstitially alloyed Ni-free nano/ultrafine grained austenitic stainless steels
2019 (English)In: Metals and Materials International, ISSN 1598-9623, E-ISSN 2005-4149, Vol. 25, no 4, p. 846-859Article in journal (Refereed) Published
Abstract [en]

The martensite reversion treatment was conducted on two grades of Ni-free austenitic stainless steels interstitially alloyed with C and N. The hot rolled sheets of steels were cold rolled up to 80% thickness reduction to acquire strain-induced α′-martensite and subsequently reversion annealed at temperatures from 700 to 850 °C for 1 to 1000 s to revert the α′-martensite to austenite. Microstructural evolution was investigated using optical microscopy, X-ray diffraction, electron backscatter diffraction, and magnetic measurement techniques. Mechanical properties were measured using tensile tests at room temperature. The resultant microstructures contained both reverted and recrystallized austenite when reverted at 700 and 750 °C with the annealing time less than 100 s. A nonuniform grain structure was characterized under these conditions consisting of nano/ultrafine grains formed via α′-martensite reversion and coarser grains by recrystallization of the retained austenite. However, a more uniform austenite grain size with average size of 1 μm was obtained at 850 °C for 1000 s. The specimens having nonuniform grain structure exhibited excellent combinations of strength and ductility. A variety of mechanical properties was achieved depending on the annealing condition. The work hardening behavior affected UTS and ductility of the studied steels. The shift of the work hardening peaks to the higher strains was found suitable for ductility. Addition of C to N-containing Ni-free steels deteriorated mechanical properties. Best combination of strength and elongation was obtained in the test material with lower C/N ratio. 

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Interstitially alloyed austenitic stainless steel, Mechanical properties, Nano/ultrafine grain size, Ni-free stainless steel, Recrystallization, Reversion annealing
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-45489 (URN)10.1007/s12540-019-00255-w (DOI)000473163200003 ()2-s2.0-85061302943 (Scopus ID)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-08-08Bibliographically approved
Vahiddastjerdi, H., Rezaeian, A., Toroghinejad, M. R., Dini, G. & Ghassemali, E. (2019). Optimizing pulsed Nd: YAG laser welding of high-Mn TWIP steel using response surface methodology technique. Optics and Laser Technology, 120, Article ID 105721.
Open this publication in new window or tab >>Optimizing pulsed Nd: YAG laser welding of high-Mn TWIP steel using response surface methodology technique
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2019 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 120, article id 105721Article in journal (Refereed) Published
Abstract [en]

In the present study, the microstructural and mechanical properties of laser beam-welded thin sheet twinning-induced plasticity (TWIP) steel were investigated. The pulsed neodymium: yttrium-aluminum-garnet (Nd: YAG) laser beam welding process parameters were modeled and optimized based on experimental data and statistical analysis using response surface methodology (RSM) technique. Process parameters range, i.e. the power input (2000–3000 W), welding speed (0.2–1 mm/min), and spot size (0.3–0.7 mm) were selected properly in order to obtain the desired mechanical properties. Main effects of each factor along with interaction effect with other factors were determined quantitatively. The predicted and actual values of the mechanical properties compared using analysis of variance (ANOVA) in order to verify the adequacy of the developed model. Optimal laser beam welding parameters were identified as the power input, welding speed and spot size of 2586 W, 0.53 mm/min, and 0.48 mm, respectively. Using parameters in the optimal conditions, a welding joint with tensile load of 2001 N (% 94 strength of the base metal) was obtained. In addition, the welding zone with an average grain size coarser than the one for the base metal and a random texture was identified.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Pulsed Nd: YAG laser welding, Twinning-induced plasticity (TWIP) steel, Response surface methodology (RSM), Optimization
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-45493 (URN)10.1016/j.optlastec.2019.105721 (DOI)000487569900046 ()2-s2.0-85070098714 (Scopus ID);JTHMaterialIS (Local ID);JTHMaterialIS (Archive number);JTHMaterialIS (OAI)
Note

PP-check JTH 2019 embargo 24 / EE

Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-10-29Bibliographically approved
Bogdanoff, T., Ghassemali, E., Riestra, M. & Seifeddine, S. (2019). Prototyping of a high pressure die cast al-si alloy using plaster mold casting to replicate corresponding mechanical properties. In: Minerals, Metals and Materials Series: . Paper presented at Light Metals Symposium held at the TMS Annual Meeting and Exhibition, 2019, San Antonio, United States, 10 - 14 March 2019 (pp. 435-442). Springer
Open this publication in new window or tab >>Prototyping of a high pressure die cast al-si alloy using plaster mold casting to replicate corresponding mechanical properties
2019 (English)In: Minerals, Metals and Materials Series, Springer, 2019, p. 435-442Conference paper, Published paper (Refereed)
Abstract [en]

Prototyping prior high pressure die casting (HPDC) is used for product/mold design optimization. Plaster mold casting is a cost-efficient prototyping technique providing good surface quality and dimension accuracy, similar to HPDC components. However, the corresponding mechanical properties of a component produced with these two methods are diverging significantly, mainly due to differences in the cooling rate. This work presents a procedure to optimize the plaster mold casting for prototyping to replicate mechanical properties of a commonly used Al-Si alloy (A380). Two commercial alloys with compositions close to the A380 alloy (A356.0 and A360.2) were used. Yield strength was considered as the main design criteria, thus the target mechanical property. Tensile testing results showed that with an optimized T6 heat treatment, not only the yield strength, but also ultimate tensile strength and elongation correspond well to the properties in the HPDC component.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Aluminium alloys, Heat treatment, Prototyping, Aluminum alloys, Die casting, Light metals, Mechanical properties, Molds, Plaster, Product design, Software prototyping, Tensile strength, Tensile testing, Yield stress, Commercial alloys, Design criteria, Design optimization, Dimension accuracy, High pressure die casting, High pressure die casts, T6 heat treatment, Ultimate tensile strength, Silicon alloys
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-43728 (URN)10.1007/978-3-030-05864-7_56 (DOI)2-s2.0-85064856753 (Scopus ID)9783030058630 (ISBN)9783030058647 (ISBN)
Conference
Light Metals Symposium held at the TMS Annual Meeting and Exhibition, 2019, San Antonio, United States, 10 - 14 March 2019
Available from: 2019-05-22 Created: 2019-05-22 Last updated: 2019-05-22Bibliographically approved
Ghassemali, E., Hernando, J. C., Stefanescu, D. M., Diószegi, A., Jarfors, A. E. .., Dluhoš, J. & Petrenec, M. (2019). Revisiting the graphite nodule in ductile iron. Scripta Materialia, 161, 66-69
Open this publication in new window or tab >>Revisiting the graphite nodule in ductile iron
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 161, p. 66-69Article in journal (Refereed) Published
Abstract [en]

The growth mechanism of graphite nodules in ductile iron was experimentally investigated using high-resolution 3D tomography of an individual graphite nodule in a near-eutectic ductile iron. The dual beam scanning electron microscopy (FIB-SEM) technique was used for this purpose. Iron particles elongated in the radial direction were observed inside a graphite nodule. Some micro-voids were detected inside the nodule, mostly located at the end of the iron particles. These observations were compared with established theories about the growth of graphite nodules and iron entrapment/engulfment in between the graphite sectors during solidification of ductile iron. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
3D reconstruction, FIB, Growth mechanism, Solidification, Ductility, Graphite, Iron, Scanning electron microscopy, 3-d tomographies, Graphite nodules, Growth mechanisms, High resolution, Iron Particles, Micro voids, Radial direction, Cast iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41986 (URN)10.1016/j.scriptamat.2018.10.018 (DOI)000450375500015 ()2-s2.0-85055115924 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2019-04-29Bibliographically approved
Hajiannia, I., Shamanian, M., Atapour, M., Ashiri, R. & Ghassemali, E. (2019). The assessment of second pulse effects on the microstructure and fracture behavior of the resistance spot welding in advanced ultrahigh-strength steel TRIP1100. Iranian Journal of Materials Science and Engineering, 16(2), 79-88
Open this publication in new window or tab >>The assessment of second pulse effects on the microstructure and fracture behavior of the resistance spot welding in advanced ultrahigh-strength steel TRIP1100
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2019 (English)In: Iranian Journal of Materials Science and Engineering, ISSN 1735-0808, Vol. 16, no 2, p. 79-88Article in journal (Refereed) Published
Abstract [en]

In this study, the effects of the second pulse resistance spot welding on the microstructure and mechanical properties of transformation induced plasticity 1100 steel were evaluated. The thermal process after welding was designed to improve metallurgical properties with pulse currents of 6 kA, 9 kA, and 12 kA after initial welding with 10 kA current. The effect of the second pulse on mechanical and microstructural properties was investigated. The fracture of the welds was for pulsed samples of 6 kA and 9 kA pull out with mechanical test. Due to the existence of the microstructure including the equiaxial dendritic and finer in fusin zone in the pulsed current of 9 kA, the maximum fracture energy, and maximum force were observed. A significant decrease in the FZ hardness in 6 kA current was observed in the nano-hardness results, which was attributed to the existence of martensitic and ferrite temper. The highest ratio of CTS/TSS was obtained for 6 kA and 9 kA, respectively, and force-displacement evaluation was maximum in 9 kA. The fracture surfaces included dendrites and dimples. The results of partial fracture revealed separation in the coherent boundaries of the coarse grain of the annealed region.

Place, publisher, year, edition, pages
Iran University of Science and Technology, 2019
Keywords
Dendritic microstructure, Fracture surface, Resistance spot welding, Second pulse current, Shear tensile
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-45390 (URN)10.22068/ijmse.16.2.79 (DOI)000472646400008 ()2-s2.0-85068678947 (Scopus ID)POA JTH 2019;JTHMaterialIS (Local ID)POA JTH 2019;JTHMaterialIS (Archive number)POA JTH 2019;JTHMaterialIS (OAI)
Available from: 2019-07-23 Created: 2019-07-23 Last updated: 2019-07-23Bibliographically approved
Hernando, J. C., Elfsberg, J., Ghassemali, E., Dahle, A. & Diószegi, A. (2019). The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys. Scripta Materialia, 168, 33-37
Open this publication in new window or tab >>The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 168, p. 33-37Article in journal (Refereed) Published
Abstract [en]

The effect of primary austenite morphology on the ultimate tensile strength (UTS) of hypoeutectic compacted graphite Fe-C-Si alloys (CGI) is studied by isothermal coarsening experiments. Secondary dendrite arm spacing (SDAS) and the morphological characteristics related to the surface area of primary austenite, M γ and D ID Hyd , increase with the cube root of coarsening time. UTS decreases linearly with increasing coarseness of primary austenite. The eutectic and eutectoid microstructures are unaffected by the primary austenite morphology. These observations demonstrate the strong influence of primary austenite morphology on the mechanical properties of hypoeutectic CGI alloys.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Coarsening, Compacted graphite iron, Dendrites, Mechanical properties, UTS, Austenite, Dendrites (metallography), Graphite, Morphology, Ostwald ripening, Silicon alloys, Tensile strength, Morphological characteristic, Primary austenite, Secondary dendrite arm spacing, Si alloys, Surface area, Ultimate tensile strength, Iron alloys
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-43550 (URN)10.1016/j.scriptamat.2019.04.010 (DOI)000470798400008 ()2-s2.0-85064563538 (Scopus ID)PP JTH 2019 embargo 24 (Local ID)PP JTH 2019 embargo 24 (Archive number)PP JTH 2019 embargo 24 (OAI)
Funder
Vinnova, 2013-03303; 2013-04720Knowledge Foundation, 2018-0033
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-08-06Bibliographically approved
Bjurenstedt, A., Ghassemali, E., Seifeddine, S. & Dahle, A. (2019). The effect of Fe-rich intermetallics on crack initiation in cast aluminium: an in-situ tensile study. Materials Science & Engineering: A, 756, 502-507
Open this publication in new window or tab >>The effect of Fe-rich intermetallics on crack initiation in cast aluminium: an in-situ tensile study
2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 756, p. 502-507Article in journal (Refereed) Published
Abstract [en]

To evaluate the role of Fe-rich intermetallics on crack initiation, two fully modified Al-Si alloys, one containing plate-like β-Fe and the second containing primary α-Fe intermetallics, were investigated by in-situ tensile testing in the scanning electron microscope. In the first alloy, large plate-like β-Fe intermetallics oriented parallel to the test direction were the first to crack at an elongation of about 1.8%. More transversely oriented intermetallics caused crack initiation in the matrix which linked up with the final fracture. In the second alloy, the cracking of α-Fe intermetallics initiated at an elongation of about 0.9%. It is concluded that large α-Fe intermetallics crack first and that clusters of α-Fe are the most potent crack initiation sites.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Al-Si alloy, Cast aluminium, Fracture mechanics, Tensile testing in SEM, α-Fe, β-Fe, Aluminum alloys, Crack initiation, Cracks, Fracture testing, Intermetallics, Materials testing apparatus, Metal testing, Scanning electron microscopy, Silicon alloys, Tensile testing
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-36962 (URN)10.1016/j.msea.2018.07.044 (DOI)000469893400058 ()2-s2.0-85064717473 (Scopus ID)
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2019-06-20Bibliographically approved
Hajiannia, I., Shamanian, M., Atapour, M., Ghassemali, E. & Ashiri, R. (2018). A microstructure evaluation of different areas of resistance spot welding on ultra-high strength TRIP1100 steel. Cogent Engineering, 5(1)
Open this publication in new window or tab >>A microstructure evaluation of different areas of resistance spot welding on ultra-high strength TRIP1100 steel
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2018 (English)In: Cogent Engineering, Vol. 5, no 1Article in journal (Refereed) Published
Abstract [en]

In this study, the microstructure of resistance spot welds of advanced ultra-high strength TRIP1100 steel was investigated. For this purpose, welding was performed after determining the best welding parameters. Four sections of the heat-affected zone (HAZ) regions were selected in the regions where the heat exchange was used to control the microstructure. Then, they were used with EBSD by scanning electron microscopy (SEM). The results showed that the TRIP1100 steel microstructure consisted of polygonal ferrites, bainites, residual austenite (RA) and martensite/austenitic islands (M/A). They also showed that the melting zone (FZ) has a lath martensite structure, and the grains are larger in packets. The structure of the martensite and different orientation grains are located in the Upper-critical area (UCHAZ). In the inter-critical region (ICHAZ), the high carbon martensitic content is higher due to the presence and the structure of ferrite and martensite. In the sub-critical region (SCHAZ), due to the tempering of martensite at a temperature below A(C1), the structure is similar to the base metal (BM), with the difference that the RA degradation reduces its structure by 50%. It was found that the RA in the BM had completely transformed. The results showed that with the movement of the BM to the weld metal, the boundaries with a low angle were increased.

Place, publisher, year, edition, pages
Cogent OA, 2018
Keywords
resistance spot weld; TRIP1100; EBSD and microstructure
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41517 (URN)10.1080/23311916.2018.1512939 (DOI)000444088300001 ()JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-09-21Bibliographically approved
Ghasemi, R., Elmquist, L., Ghassemali, E., Salomonsson, K. & Jarfors, A. E. .. (2018). Abrasion resistance of lamellar graphite iron: Interaction between microstructure and abrasive particles. Tribology International, 120, 465-475
Open this publication in new window or tab >>Abrasion resistance of lamellar graphite iron: Interaction between microstructure and abrasive particles
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 120, p. 465-475Article in journal (Refereed) Published
Abstract [en]

This study focuses on abrasion resistance of Lamellar Graphite Iron (LGI) using microscratch test under constant and progressive load conditions. The interactions between a semi-spherical abrasive particle, cast iron matrix and graphite lamellas were physically simulated using a sphero-conical indenter. The produced scratches were analysed using LOM and SEM to scrutinise the effect of normal load on resulting scratch depth, width, frictional force, friction coefficient and deformation mechanism of matrix during scratching. Results showed a significant matrix deformation, and change both in frictional force and friction coefficient by increase of scratch load. Furthermore, it was shown how abrasive particles might produce deep scratches with severe matrix deformation which could result in graphite lamella's coverage and thereby deteriorate LGI's abrasion resistance.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Lamellar graphite cast iron; Abrasion resistance; Scratch test; Microstructure; Pearlite deformation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-38473 (URN)10.1016/j.triboint.2017.12.046 (DOI)000428102900046 ()2-s2.0-85041480396 (Scopus ID)
Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2019-02-15Bibliographically approved
Riestra, M., Bjurenstedt, A., Bogdanoff, T. & Ghassemali, E. (2018). Complexities in the assessment of melt quality. Paper presented at Symposium on Light Metals Alliance - Light Metals Technology (LMT) held during the Conference on Materials Science and Technology (MS and T), October 8, 2017, Pittsburgh, PA, USA. International Journal of metalcasting, 12(3), 441-448
Open this publication in new window or tab >>Complexities in the assessment of melt quality
2018 (English)In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193, Vol. 12, no 3, p. 441-448Article in journal (Refereed) Published
Abstract [en]

If high-performance aluminium castings are to be produced, the melt quality needs to be properly assured. Multiple tests for melt quality assessment exist and have previously been analysed. In most studies, the techniques were used separately. In this work, reduced pressure, fluidity, Prefil and tensile tests were evaluated. A commercial EN 46000 alloy was used as the base material with additions of 25 and 50 wt% machining chips to degrade the melt quality. In reduced pressure and fluidity tests, oxides floated to the top of samples, decreasing the reliability. Bifilm index increased with addition level, but not correspondingly. Density index, Prefil and fluidity tests did not present significant variations, and tensile properties only deteriorated with the 50 wt% addition level. The investigated techniques provided information, but measuring the melt quality reliably remains a challenge.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
melt quality; reduced pressure test; fluidity; tensile properties; Prefil; hydrogen content
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-38003 (URN)10.1007/s40962-017-0179-y (DOI)000436927100005 ()2-s2.0-85049321529 (Scopus ID)
Conference
Symposium on Light Metals Alliance - Light Metals Technology (LMT) held during the Conference on Materials Science and Technology (MS and T), October 8, 2017, Pittsburgh, PA, USA
Available from: 2017-11-28 Created: 2017-11-28 Last updated: 2019-02-14Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7527-719X

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