Microstructure and Vickers hardness of mechanically alloyed and spark plasma sintered Ti-2Zn-22Si-11B and Ti-6Zn-22Si-11B alloys

Effect of Cobalt Doping and Milling Time on Microstructure and Vickers Microhardness of the Spark Plasma Sintered (67-x)Ti-xCo-22Si-11B (x = 2 and 6 at-%) Alloys

“…The 65Ti-2Co-22Si-11B and 61Ti-6Co-22Si-11B alloys presented the values between 950-1050 HV and 1050-1150 HV, respectively. In contrary, the SPSed Ti-2Zn-22Si-11B alloy presented average Vickers hardness values higher than 1050 HV whereas the SPSed Ti-6Zn-22Si-11B alloy varied between 970 and 1036 HV, which were associated with the Ti 6 Si 2 B formation 4 . Considering the SPSed Ti-Co-22Si-11B and Ti-2Sn-22Si-11B alloys are based on Ti 6 Si 2 B as matrix, and both the Co and Tin solubility limits in Ti 6 Si 2 B are closed to 2 at-%, their Vickers microhardness values of these quaternary alloys can be related with a more effective (Ti,Sn) 6 Si 2 B solution strengthening.…”

“…Cobalt granules with 99 wt.-% purity (Dinâmica Ltda., Indaiatuba, SP, Brazil) were used to prepare the quaternary alloys. In order to evaluate the effect of cobalt addition on the Ti 6 Si 2 B stability, the added amounts were chosen in accordance with previous works involving the Ti-Sn-Si-B 4 and Ti-Zr-Si-B 5 alloys produced by similar route with same alloying amounts.…”

“…Ball milling from elemental Ti-Co-Si-B powder mixtures was performed in a planetary Fritsch P-5 mill (Fritsch GmbH, Idar-Oberstein, Germany) under argon atmosphere using WC-6Co vials (225 mL) and balls (19 mm diameter), rotary speed of 300 rpm and a ball-to-powder weight ratio of 10:1. To understand the effect of milling time on phase transformation, the elemental Ti-Co-Si-B powder mixtures were milled at different times (20,60, and 300 min), which are based on the previous work 4 .…”

“…Nonetheless, the use of alloying and its effect on phase transformations during processing and specific mechanical properties are important. Previous studies on phase transformations in mechanical alloyed (67-x)Ti-xMe-22Si-11B (x ≤ 6 at-%) powders containing the Sn 4 or Zr 5 addition lower than 2 and 6 at-% can produce microstructures based on Ti 6 Si 2 B. For higher amounts, the Ti 5 Si 3 or Ti 3 Si phases dissolving alloying elements are preferentially formed instead the Ti 6 Si 2 B phase in the Ti-Si-B alloys containing alloying addition.…”