过共析Ti-Cr合金的机械合金化

Mechanical alloying of hypereutectoid Ti - Cr alloys

以钛、铬元素粉为原料,在行星式球磨机上采用φ20mm的淬火钢球,以200 r/min的球磨速度和15:1的球料比,研究了Ti-20％Cr(w(B))和Ti-30％cr(w(B))两种合金的机械合金化(MA)规律.研究结果表明:在球磨初期的2 h内钛的(011)主衍射峰强度迅速降低,(010)第二衍射峰强度提高并成为最强峰,同时铬的衍射峰强度提高;随着球磨时间的增加,钛和铬的x射线衍射峰均发生宽化、强度下降和衍射角左移并减小;当球磨时间为30～40 h时,钛逐步非晶化,但在本试验条件下铬没有发生非晶化;MA的前10 h是粉末晶粒细化、晶格应变和合金化进行的最迅速的时期,经该阶段球磨后铬的晶粒尺寸可以达到20 nm,进一步球磨有利于获得过饱和固溶的合金粉末;两种合金在超过100 h的MA过程中均未发现在固相合成Laves相TiCr2;确定30～40 h为制备纳米晶或非晶过饱固溶Ti-Cr合金粉末的合理球磨时间.

The mechanical alloying of both Ti - 20wt% Cr and Ti - 30wt% Cr alloys with elemental titanium and chromium powders as raw materials is investigated in a planetary milling machine with a milling-ball having: powder weight ratio 15: 1 at 200 r/min. The results show that the intensity of the first strongest (011) peak of titanium in the XRD pattern rapidly decreases during the first 2 hours milling, but that of the second strongest (010) peak increases, which then becomes the first strongest peak, as those of the peaks of chromium do at the same time. With increasing ball-milling time, the X - ray diffraction peaks of both titanium and chromium become broader and have a tendency to move to the left toward small angle and their intensities decrease. An amorphization of titanium gradually takes place as the milling time reaches 30 to 40 hours, but no amorphization of chromium is observed in the whole test. It is in the first 10 hours ball milling period that the rate of grain refining, crystal lattice deformation and alloying appears highest and successive milling is extremely important for the fabrication of supersaturation alloyed powders. No Laves phase has been found even with milling time up to over 100 hours for both test alloys, 30-40 hours milling is finally considered as rational for the fabrication of nano-and/or amorphous supersaturation Ti - Cr alloyed powders.