(陜西理工大學(xué) 材料科學(xué)與工程學(xué)院，漢中 723001)
摘 要: 采用X射線衍射儀、示差掃描量熱儀、激光掃描共聚焦顯微鏡、TEM和拉伸實(shí)驗(yàn)研究了時(shí)效溫度(tag)對(300，400，500，600 ℃；1 h)時(shí)效態(tài)Ti-50.8Ni-0.1Nb形狀記憶合金相變、組織和形狀記憶行為的影響。結(jié)果表明：300~600 ℃時(shí)效態(tài)Ti-50.8Ni-0.1Nb合金的相組成為B2和B19′。隨tag升高，合金冷卻/加熱相變類型發(fā)生由A→R→M/M→R→A型向A→M/M→A型轉(zhuǎn)變(A—母相B2，CsCl結(jié)構(gòu)；R—R相，菱方結(jié)構(gòu)；M—馬氏體相B19′，單斜結(jié)構(gòu))，R相變溫度先升高后降低，M相變溫度先降低后升高再降低；R和M相變熱滯分別在3.8~12.0 ℃和8.7~131.7 ℃之間變化。隨tag升高，合金中Ti3Ni4析出相的形態(tài)發(fā)生由點(diǎn)狀→針狀→透鏡狀→片狀轉(zhuǎn)變。400、 500 ℃時(shí)效態(tài)合金的抗拉強(qiáng)度高于300、600 ℃時(shí)效態(tài)合金的，其伸長率則低于后者。300、400、600 ℃時(shí)效態(tài)合金呈超彈性，500 ℃時(shí)效態(tài)合金呈形狀記憶效應(yīng)。隨應(yīng)力-應(yīng)變循環(huán)次數(shù)增加，合金的應(yīng)力-應(yīng)變曲線平臺(tái)應(yīng)力下降并趨穩(wěn)，300、400 ℃時(shí)效態(tài)合金的超彈性穩(wěn)定性良好。
關(guān)鍵字: Ti-50.8Ni-0.1Nb合金；形狀記憶合金；時(shí)效溫度；相變；形狀記憶行為
（School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723001, China）
Abstract:The effect of aging temperature (tag) on the phase transformation, microstructure, and shape memory behaviors of Ti-50.8Ni-0.1Nb shape memory alloy aged at 300, 400, 500 and 600 ℃ for 1 h, respectively, were investigated by means of X-ray diffractometry, differential scanning calorimetry, laser scanning confocal microscope, TEM and tensile test. The results show that the phase compositions of Ti-50.8Ni-0.1Nb alloy aged at 300-600 ℃ are B2 and B19′. With increasing tag, the transformation types of the alloy change from A→R→M/M→R→A to A→M/M→A (A—parent phase B2, CsCl; R—R phase, rhombohedral; M—martensite B19′, monoclinic) upon cooling/heating; the R phase transition temperature increases first and then decreases, and the M transition temperature decreases first, then increases and then decreases; the R and M temperature hysteresis change in the range of 3.8-12.0 ℃ and 8.7-131.7 ℃, respectively. With increasing tag, the morphology of Ti3Ni4 precipitates in the alloy changes from granular → acicular → lenticular → flaky. The tensile strength of the alloy aged at 400 ℃ and 500 ℃ is higher than that of the alloy aged at 300 ℃ and 600 ℃, while the percentage elongation of the former is lower than that of the latter. The alloys aged at 300, 400, 600 ℃ show superelasticity, and the alloy annealed at 500 ℃ shows shape memory effect. With increasing stress-strain cycling number, the platform stress in the stress-strain curve of the alloy decreases. The stability of the superelasticity in the alloy aged at 300 ℃ and 400 ℃ is excellent.
Key words: Ti-50.8Ni-0.1Nb alloy; shape memory alloy; aging temperature; phase transformation; shape memory behavior
