【摘要】：TiNi合金因具有形狀記憶效應(yīng)及良好的力學(xué)性能而廣泛應(yīng)用于航空航天、民用工業(yè)領(lǐng)域;超高壓影響材料新相的形成,超高壓不同時(shí)效工藝對(duì)TiNi合金組織性能有著重要影響,采用X射線衍射技術(shù)、透射電子顯微鏡、差示掃描量熱、拉伸試驗(yàn)、硬度測(cè)試系統(tǒng)研究超高壓不同時(shí)效工藝對(duì)Ti-51(at%)Ni合金顯微組織形貌、馬氏體相變及力學(xué)性能的影響。試驗(yàn)結(jié)果表明,超高壓時(shí)效,隨著溫度的升高或時(shí)間的增長(zhǎng),尺寸逐漸增大,Ti3Ni4析出相逐漸由顆粒狀長(zhǎng)大為橢圓透鏡狀、橢圓薄片狀,最終長(zhǎng)大為粗片狀,隨著壓力增大,析出相尺寸減小;超高壓導(dǎo)致晶粒內(nèi)部形成高密度位錯(cuò),高壓時(shí)效晶界處與晶粒內(nèi)部析出相分布并無(wú)明顯差異;隨著時(shí)效溫度的升高,合金由兩步相變轉(zhuǎn)變?yōu)橐徊较嘧?隨著時(shí)效時(shí)間的增長(zhǎng),合金由兩步相變逐漸轉(zhuǎn)變?yōu)槿较嘧?隨著壓力的增大,合金由一步相變轉(zhuǎn)變?yōu)閮刹较嘧?進(jìn)一步轉(zhuǎn)變?yōu)槿较嘧?室溫下拉伸,高壓不同溫度時(shí)效抗拉強(qiáng)度在600℃達(dá)到最大為960MPa,延伸率最大為19.2%,硬度在500℃達(dá)到最大為382.4HV;高壓不同時(shí)間時(shí)效,抗拉強(qiáng)度在2h達(dá)到最大為1150MPa,延伸率最大為18%,硬度在5h達(dá)到最大為433.9HV;不同壓力時(shí)效,抗拉強(qiáng)度在5.5GPa達(dá)到最大為960MPa,延伸率在1GPa達(dá)到最大為22%,硬度在3GPa達(dá)到最大為404.7HV。試驗(yàn)分析表明,高壓使擴(kuò)散系數(shù)減小,高壓時(shí)效下Ti3Ni4析出相的尺寸小于常壓時(shí)效析出相的尺寸,隨著壓力的增大,Ti3Ni4析出相顯著細(xì)化;超高壓導(dǎo)致高密度位錯(cuò),為析出相形核提供動(dòng)力,使得析出相晶內(nèi)與晶界分布沒(méi)有明顯差別;Ti3Ni4析出相與基體呈共格或半共格關(guān)系,使局部應(yīng)力不均,導(dǎo)致R相變產(chǎn)生;Ti3Ni4析出相導(dǎo)致內(nèi)部成分不均勻分布,使得馬氏體相變溫度發(fā)生變化,導(dǎo)致三步相變產(chǎn)生;超高壓不同工藝時(shí)效TiNi合金,析出相細(xì)化及高密度位錯(cuò)的形成改善了力學(xué)性能。在綜合分析超高壓不同時(shí)效工藝對(duì)TiNi合金顯微組織結(jié)構(gòu)及馬氏體相變、力學(xué)性能的影響規(guī)律和機(jī)制的基礎(chǔ)上,確定了高壓時(shí)效與常壓時(shí)效不同的根本原因在于高壓使擴(kuò)散系數(shù)減小以及產(chǎn)生高密度位錯(cuò),導(dǎo)致Ti3Ni4析出相分布及大小不同,進(jìn)一步影響馬氏體相變及力學(xué)性能。
[Abstract]:TiNi alloy is widely used in aerospace and civil industry because of its shape memory effect and good mechanical properties. Ultra-high pressure affects the formation of new phase of TiNi alloy, and different aging processes have an important effect on microstructure and properties of TiNi alloy. X-ray diffraction technique, transmission electron microscope, differential scanning calorimetry, tensile test are used. The effects of different aging processes on the microstructure, martensite transformation and mechanical properties of Ti-51 (at%) Ni alloy were investigated by hardness measurement system. The experimental results show that with the increase of temperature or time, the size of Ti3Ni4 precipitates gradually increases, and the precipitates of Ti3Ni4 gradually grow from granular to elliptical lens, elliptical thin slice, and finally grow to coarse flake, and increase with the increase of pressure. The size of precipitated phase decreases; High density dislocation is formed in the grain due to ultra-high pressure, and there is no obvious difference between the precipitation phase distribution at the high pressure aging grain boundary and that in the grain. With the increase of aging temperature, the alloy changes from two-step transformation to one-step phase transformation, with aging time increasing, the alloy gradually changes from two-step phase to three-step phase transition, and with the increase of pressure, the alloy changes from one-step phase to two-step phase transition. Further transformation into three-step phase transition; At room temperature, the maximum aging tensile strength at 600 鈩，

本文編號(hào)：2379355