The development of the automotive industry leads to the search for newer construction materials, but also those used in the production process. Although many types of joints are used in vehicles, resistance welds remain the dominant one. The commonly used alloy for welding caps (CuCrZr) is already well known and therefore newer alloys and technologies for their production are sought to increase service life, and thus reduce production costs. Precipitation hardening CuCrTiAl alloy was analysed in this article. After casting, CuCrTiAl alloy was subjected to cold and hot deformation and then tested for its usability. The obtained results confirmed the potential of this alloy to make electrodes for resistance welding

Domagała-Dubiel, J.

Głuchowski, W.

Maleta, M.

Sadzikowski, M.

Łagoda, M.

English

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831METALURGIJA 61 (2022) 3-4, 831-834M. ŁAGODA, W. GŁUCHOWSKI, M. MALETA, J. DOMAGAŁA-DUBIEL, M. SADZIKOWSKI CHARACTERISTICS OF CuCrTiAl  ALLOY AFTER PLASTIC DEFORMATIONReceived – Primljeno: 2021-10-30Accepted – Prihvaćeno: 2022-03-10Preliminary Note – Prethodno priopćenjeThe development of the automotive industry leads to the search for newer construction materials, but also those used in the production process. Although many types of joints are used in vehicles, resistance welds remain the dominant one. The commonly used alloy for welding caps (CuCrZr) is already well known and therefore newer alloys and technologies for their production are sought to increase service life, and thus reduce production costs. Precipitation hardening CuCrTiAl alloy was analysed in this article. After casting, CuCrTiAl alloy was subjected to cold and hot deformation and then tested for its usability. The obtained results confirmed the potential of this alloy to make electrodes for resistance welding.Key words: CuCrTiAl alloy, plastic deformation, precipitation hardening, microstructure,mechanical propertiesISSN 0543-5846METABK 61(3-4) 831-834 (2022)UDC – UDK 546.46.76.821.621:539.374:621.785:620.17:620.18=111INTRODUCTIONThere are many studies on resistance spot welding [1,2] and the phenomena occurring during it, both in the electrode and in the welded material [3-6]. They focus mainly on the currently used alloy (CuCrZr). However, there are also other alloys and materials in the literature that could theoretically replace those currently used [7,8]. There are studies on modifications to the technol-ogy of producing welding caps [9], which are aimed at improving their operational parameters, and thus reduc-ing operating costs [10]. This topic is so interesting that there were even attempts to use modern severe plastic deformation technologies in order to improve the prop-erties of the CuCrZr alloy [11].Bearing in mind the above, it was found that it is im-portant to use the knowledge of phenomena in the field of not only the selection of alloys for specific applications, but also the impact of plastic forming and heat treatment technology in the search for better usability of materials for welding caps. Only the combination of all three issues gives hope for improving the properties of resistance welding electrodes. To achieve the assumed goals, knowledge from articles [12,13] and the team members` experience were used to develop the CuCrTiAl alloy and its heat and plastic treatment technology.EXPERIMENTAfter testing many CuCrTiAl alloys, alloy shown in Table 1 was determined for further research.Table 1 Chemical composition of used CuCrTiAl alloy/wt.%Cr Ti Al Cu0,81 0,24 0,064 balanceThis alloy was cast by continuous horizontal cast-ing. Figure 1 shows a block diagram of the research car-ried out.The experiments were carried out on samples with dimensions of ø 14 x 20 mm. Heating to hot deforma-tion was carried out using an induction coil, where the heating time was 30 seconds. The temperature was con-trolled using an Optris pyrometer, and the compression strain rate was 10 s-1. After hot deformation, the samples were cooled in water. Cold deformation was carried out on samples with the same geometry, but with a strain rate of 10-1 s-1. The set deformation in both cases was similar and amounted to about 60 %. Hardness was M. Łagoda (marek.lagoda@imn.gliwice.pl), W. Głuchowski, M. Male-ta, J. Domagala-Dubiel, Łukasiewicz Research Network – Institute of Non-Ferrous Metals, Gliwice, Poland; M. Sadzikowski, AGH Univer-sity of Science and Technology, Kraków, Poland Figure 1 Scheme of the experiment.832  METALURGIJA 61 (2022) 3-4, 831-834M. AGODA et al.: ARA TERISTI S O  u rT Al ALLOY A TER PLASTI  DE ORMATIONmeasured using the Vickers method and conductivity using the eddy current method on all samples. A Future-Tech FM-700 microhardness tester and a Foester Sig-matest 2.069 device were used for the tests. Addition-ally, structure studies were carried out using scanning microscopy of selected variants. RESULTSThe cast bars were characterized by the conductivity of 25,4 MS/m and the hardness of 97 HV. Due to the small diameter of the bars and the intensive cooling dur-ing casting, aging was carried out without prior super-saturation, the purpose of which was to check the qual-ity of supersaturation during casting. The results of this experiment are shown in Figures 2 and 3.The experiment showed no significant effect of su-persaturation on the effects of aging. However, in order to maintain the purity of the measurement, it was de-cided to use the supersaturation treatment for all tested variants.Next, cold and hot deformation tests were carried out (Figures 4 and 5)Results show that in the case of hot deformation in the tested alloy, although higher deformation tempera-tures improve the hardness, they worsen the conductiv-ity, and the intermediate temperatures (800 and 850 °C) have the tested parameters at the level of the commer-cial CuCrZr alloy, the conductivity of which is 44-48 MS/m, and the hardness of 140-166 HV after plastic working and heat treatment. The most interesting result, however, is the sample aged after cold deformation, which after 90 minutes of aging achieved the hardness of 166 HV, i.e., in the upper limit of the conventional alloy, and the conductivity of 44,5 MS/m.The hot-deformed and aged sample had a homoge-neous structure (Figure 6a). Energy Dispersive Spec-troscopy (EDS) analysis (Figure 6b) showed primary precipitates of chromium (point 3 in Figure 6b) and Ti and Al oxide particles.The grain size in the material after cold deformation and aging, was similar to that in the material after hot deformation (850 °C) and aging (Figure 7a), however, in this variant, the primary precipitates of chromium are visible at the grain boundaries in the structure. Addition-ally, Ti and Al oxide particles were identified (Figure 7b).Figure 2  The influence of aging time on the conductivity of cast CuCrTiAl alloy.Figure 3 T he influence of aging time on the hardness of cast CuCrTiAl alloy.Figure 4  The influence of aging time on the conductivity of pressed CuCrTiAl alloy833M. AGODA et al.: ARA TERISTI S O  u rT Al ALLOY A TER PLASTI  DE ORMATIONMETALURGIJA 61 (2022) 3-4, 831-834SUMMARY1. The tested CuCrTiAl alloy after continuous casting to the size of ø 14 mm does not require supersatura-tion, because both samples without and with super-saturation after aging at 480 °C maintain compara-ble conductivity and hardness.2. Hot deformation of the tested alloy at the tempera-tures of 800 and 850 °C followed by aging causes an increase in conductivity and hardness to the level of the CuCrZr alloy currently used for the welding caps.3. Cold deformation and aging allowed the tested alloy to obtain high hardness (166 HV) and satisfactory conductivity (44,5 MS/m).4. Although the structure of the cold-deformed and aged material has a grain size similar to that of the hot-deformed and aged sample, it shows a strong lo-calization of primary chromium precipitates at the grain boundaries.5. Cu0.8Cr0.2Ti0.1Al alloy, both after cold and hot de-formation, shows comparable conductivity and hardness, which will be the subject of further re-search.Figure 5  The influence of aging time on the hardness of pressed CuCrTiAl alloy.Figure 6 Microstructure and EDS analysis of the CuCrTiAl alloy after hot deformation and aging at 480 °C for 2 hours, where the individual points have the following chemical composition (wt. %): 1. Cu-97,8, Cr-2,1, Al-0,1; 2. Cu-99,4, Cr-0,6; 3. Cu-5,1, Cr-82,4, Ti-3,2, P-9,2; 4. Cu-50,8, Cr-2,7, Ti-0,2, Al-26,2, O-20,1; 5. Cu-99,3, Cr-0,6, Al-0,1.Figure 7 Microstructure a) and EDS analysis of the CuCrTiAl alloy after cold deformation and aging at 480 °C for 90 minutes, where the individual points have the following chemical composition (wt. %): 1. Cu = 99,10, Cr = 0,62, Al = 0,28; 2. Cu = 85,24, Cr = 14,46, Ti = 0,15, Al = 0,15; 3. Cu = 94,20, Cr = 5,56, Al = 0,24; 4. Cu = 99,09, Cr = 0,61, Ti = 0,04, Al = 0,26; 5. Cu = 35,78, Cr = 63,38, Ti = 0,16, O = 0,65, Al = 0,04; 6. Cu = 79,80, Cr = 1,60, Ti = 6,81, O = 7,36, Al = 4,43; 7. Cu = 71,24, Cr = 27,68, Ti = 0,19, O = 0,85, Al = 0,03; 8. Cu = 99,05, Cr = 0,80, Al = 0,14.a)b)a)b)834  METALURGIJA 61 (2022) 3-4, 831-834M. AGODA et al.: ARA TERISTI S O  u rT Al ALLOY A TER PLASTI  DE ORMATIONAcknowledgementThe authors are pleased to acknowledge the help of Professor Z. Rdzawski in the discussion.The work received funding from the project: TECH-MATSTRATEG1 / 347960/6 / NCBR / 2017REFERENCES[1] E. Gauthier, D. Carron, P. Rogeon, P. Pilvin, C. Pouvreau., T. 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Characteristics of CuCrTiAl alloy after plastic deformation

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