بررسي تاثير زمان آسياب بر تحولات فازي كامپوزيت زمينه TiB2 تهيه شده به روش SHS

Effect of milling time on phase transformations in TiB2 based composite prepared by SHS method

در تحقيق حاضر از مواد اوليه عنصري، شامل پودرهاي تيتانيوم فلزي، بور و گرافيت جهت دستيابي به تركيب پودري TiB2 تقويت شده با ذرات كاربيد تيتانيوم استفاده شد. مخلوط فوق در زمانهاي 1 تا 6 ساعت تحت عمليات آسياب پر انرژي قرار گرفت و پودرهاي حاصله، از طريق فرآيند SHS سنتز شدند. با بررسي طيف XRD پودرهاي آسيا شده و پيگيري توالي آنها ثابت گشت كه مقداري TiB2 و TiC هر چند اندك نيز در حين آسياكاري تشكيل شد كه اين امر با افزايش اين زمان تا 6 ساعت، نمود بيشتري داشت. سنتز پودر با زمان آسياب بالا با موفقيت بيشتري نيز همراه گشت به طوريكه مقدار فازهاي ناخواسته و مياني از قبيل TiB و B4C به حداقل ميزان خود در محصولات رسيد. علاوه بر اين، عمليات مذكور سبب شد تا دماي لازم جهت شروع واكنش نيز حدود 200 درجه سانتيگراد كاهش يابد. از سوي ديگر نتايج حاصل از پهن شدگي پيك هاي XRD نشان داد كه افزايش زمان آسياب در كاهش اندازه ذرات محصول تا 50nm و اكتيو نمودن آنها در جهت تسهيل فرآيند SHS و فزايش خلوص محصولات نقش انكار ناپذيري دارد. نتايج حاصل از آناليز SEM نشانگر محصولي با ريز ساختار نسبتا يكنواخت، ريزدانه و متخلخل بود.

Today TiB2 has been considered as one of the most advanced materials in the manufacturing of the advanced industrial components. The SHS method as one of the most common and most economical method to synthesis above components is proposed which can be associated with the pre-milling operation. In this present investigation, elemental raw materials including titanium metal, boron and graphite powders were used to achieve TiB2 component which reinforced with titanium carbide particles. The above mixture was milled for 1 up to 6 h at the high energy ball mill and the milled powders were synthesized by the SHS process. Investigation of XRD patterns of milled powders showed a few amount of TiB2 and TiC were formed during the milling process at 6 h milling time. The milled powders were synthesized with longer milling time was also associated with greater success however the amount of unwanted and intermediate phases such as TiB and B4C were reached at least amount in the products. In addition, the above technique led to the ignition temperature for the reaction was reduced about 200oC. On the other hand, the results of broadening of XRD peaks showed increasing of milling time led to reducing the particle size to 50 nm and the activation of them in order to facilitate the SHS process and increasing the purity of the products is undeniable role. The results of SEM analysis showed the product with a relatively uniform microstructure and fine-grained and porous.