Zhao Yanjun, Lu Zepeng, Mi Li, Hu Zhiliu, Yang Wenchao
College of Resources, Environment and Materials, Guangxi University, Nanning 530004, China.
Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, Guangxi University, Nanning 530004, China.
Materials (Basel). 2022 Mar 8;15(6):1984. doi: 10.3390/ma15061984.
Three different Ti addition routes were used to prepare an Al-5Ti-B Master Alloy: the halide salt route, the Ti-sponge route, and the partial Ti-sponge route. In the halide salt route, the raw materials were Al + KBF + KTiF; KTiF was completely replaced by pure titanium for the Ti-sponge route versus the halide salt route; in the partial Ti-sponge route, KTiF was partially replaced by pure titanium. Here, 30% Ti-sponge or 60% Ti-sponge route means that 30% or 60% KTiF was replaced by pure titanium, respectively. The above Ti addition routes have a significant influence on the growth pattern and morphological evolution of TiAl and TiB, which greatly affect the refining performance of Al-Ti-B Master Alloy. When using the halide salt route, a streamlined "rich Ti, B area" exists in the aluminum melt, which is a complex compound of (Ti, Al) B. The "rich Ti, B area" is essential for the nucleation and growth of TiAl and TiB. Blocky TiAl was obtained and its average size was 4.7 μm based on the halide salt route. In the Ti-sponge route, the nucleation of TiAl mainly depends on the mutual diffusion of Al and Ti, and TiAl forms around pure Ti particles, i.e., the so-called Ti-TiAl mechanism. The average size of the blocky TiAl was 9.8 μm based on the Ti-TiAl mechanism. For the partial Ti-sponge route, the "rich Ti, B area" gradually decreases with the increase in Ti powder's contents, and large TiAl coexists with the small TiAl. Compared with the Ti-sponge route, the halide salt route can form smaller TiAl. In the Ti-sponge route, there is a small amount of "rich Ti, B area" due to the influence of the Ti-TiAl mechanism, which does not meet the requirements of TiB growth. In the halide salt route, there is sufficient "rich Ti, B area", which is conducive to the formation of TiB. Both the crystal defects and the crowded growth environment caused by the "rich Ti, B area" are fundamental reasons for the fragility and the irregular shape of the TiB. The refining effect of the Al-Ti-B Master Alloy prepared by the halide salt route is better than the Ti-sponge route. The refining effect of 30% Ti-sponge route is better than that of Ti-sponge route and worse than that of halide salt route.
采用三种不同的钛添加路线制备Al-5Ti-B中间合金：卤化物盐路线、海绵钛路线和部分海绵钛路线。在卤化物盐路线中，原料为Al + KBF + KTiF；与卤化物盐路线相比，在海绵钛路线中KTiF完全被纯钛取代；在部分海绵钛路线中，KTiF被纯钛部分取代。这里，30%海绵钛或60%海绵钛路线分别意味着30%或60%的KTiF被纯钛取代。上述钛添加路线对TiAl和TiB的生长模式及形态演变有显著影响，这极大地影响了Al-Ti-B中间合金的细化性能。采用卤化物盐路线时，铝熔体中存在流线型的“富Ti、B区域”，它是(Ti, Al)B的一种复杂化合物。“富Ti、B区域”对TiAl和TiB的形核与生长至关重要。基于卤化物盐路线获得了块状TiAl，其平均尺寸为4.7μm。在海绵钛路线中，TiAl的形核主要取决于Al和Ti的相互扩散，TiAl在纯Ti颗粒周围形成，即所谓的Ti-TiAl机制。基于Ti-TiAl机制，块状TiAl的平均尺寸为9.8μm。对于部分海绵钛路线，“富Ti、B区域”随着钛粉含量的增加而逐渐减少，大尺寸TiAl与小尺寸TiAl共存。与海绵钛路线相比，卤化物盐路线能形成尺寸更小的TiAl。在海绵钛路线中，由于Ti-TiAl机制的影响，存在少量“富Ti、B区域”，这不符合TiB生长的要求。在卤化物盐路线中，有足够的“富Ti、B区域”，有利于TiB的形成。“富Ti、B区域”导致的晶体缺陷和拥挤生长环境是TiB脆性和形状不规则的根本原因。采用卤化物盐路线制备的Al-Ti-B中间合金的细化效果优于海绵钛路线。30%海绵钛路线的细化效果优于海绵钛路线且劣于卤化物盐路线。
