Dispersion Hardening and Super-Plastic Titanium Alloys Prepared by Mechanical alloying, and Their Deformation Modes

近三年来的研究结果对阐明机械合金化的力学化学势及其在材料工程中的应用局限具有重要意义。1)即使熔体法难以制备的合金体系，只要球磨能量足够高，也能完全制备固溶合金。2) MA的致命缺陷是钢质球磨机的污染。钛球磨机用于防止污染。但是MA的势能下降，从而与球的重量成正比。3)由于钛具有化学活性，5N、4N纯度载气Ar、N_2等需用加热至523K以上的海绵钛净化，以防止粉末表面氧化。Ar气体的脱氧促进了MA粉在球磨机上的粘着。用钛球磨机在144ks MA中，脱氧的N_2有溶解8mass%N作为氮化TiN的潜力。TiN在高压下解离成Ti-N固溶体。4)将Ti-9.5 v -2.5 mo - 3ai混合粉末用Ti球磨机机械合金化432ks后，合金体系变为β型固溶体粉末，料样具有超塑性。5)对几种MA粉末进行了热应力处理（1270K, 100MPa）的固结试验。由Ti-Mo， Ti-V-Mo-Al， Ti-N的MA粉末制成的HIP试样在冷却至300K，减压至O. lMPa时发生失效。MA和HIP处理的后效导致固结试样的延性显著降低。6) MA的工程应用取决于粉末固结的成功与否，而粉末保持了作为散装样品的延展性。

The following results obtained for the past three years are very important to clarify the mechanochemical potentials about mechanical alloying(MA)and the limits of the application to materials engineering.1)As long as the ball milling energy is high enough, solid solution alloy is completely performed even for the alloy system being difficult to prepare by melt method.2)The fatal defect of MA is contamination from the ball mill made of steel. The titanium ball mill is used to prevent the contamination. But the potential energy of MA drops so as to be proportional to the weight of the balls.3)As titanium is chemically active, the 5N and 4N purity carrier gases, Ar, N_2 etc., should be'purified with sponge titanium heated above 523K in order to prevent the surface oxidation of powder. The deoxidation of Ar gas promotes sticking of MA powder to the ball mill. The deoxidized N_2 has a potential of solving 8mass%N as nitride TiN in Ti matrix for 144ks MA with Ti ball mill. TiN is dissociated to Ti-N solid solution at high pressure.4)When the mixed powder of Ti-9.5V-2.5Mo-3AI is mechanically alloyed for 432ks with Ti ball mill, the alloy system becomes to beta solid solution powder expected to be super-plastic in bulk sample.5)The consolidation of some kinds of MA powder is tried by HIP treatment(1270K, 100MPa). Failures of HIP sample made of MA powder of Ti-Mo, Ti-V-Mo-Al, Ti-N take place during cooling to 300K and reducing pressure to O. lMPa. The after effect of MA and HIP treatments cause drastically decreasing the ductility of the consolidated samples.6)The engineering application of MA depends on the success of the consolidation of powders which remains ductility as the bulk sample.