鈦及(ji)鈦合(he)金(jin)(jin)(jin)(jin)(jin)具有(you)高的(de)(de)(de)(de)抗(kang)拉強(qiang)度(du)和(he)抗(kang)疲勞強(qiang)度(du)、低的(de)(de)(de)(de)彈性(xing)模量、低密度(du)以及(ji)良(liang)好的(de)(de)(de)(de)抗(kang)腐蝕性(xing)能(neng)，被(bei)廣泛(fan)應(ying)用(yong)于航(hang)空航(hang)天、海洋工程(cheng)以及(ji)生(sheng)物(wu)醫(yi)學領域[1,2]。Ti80合(he)金(jin)(jin)(jin)(jin)(jin)是我國自行研(yan)發的(de)(de)(de)(de)875MPa級近α型鈦合(he)金(jin)(jin)(jin)(jin)(jin)，其(qi)名義成分(fen)(fen)為Ti-6Al-3Nb-2Zr-1Mo（質量分(fen)(fen)數,%），合(he)金(jin)(jin)(jin)(jin)(jin)元(yuan)素的(de)(de)(de)(de)添加使其(qi)比(bi)傳統船用(yong)TC4合(he)金(jin)(jin)(jin)(jin)(jin)具有(you)更優良(liang)的(de)(de)(de)(de)耐(nai)蝕性(xing)、強(qiang)韌(ren)性(xing)、可焊(han)性(xing)等突(tu)出優勢，被(bei)廣泛(fan)應(ying)用(yong)于船舶(bo)的(de)(de)(de)(de)受(shou)力結構(gou)、深(shen)海潛(qian)水器的(de)(de)(de)(de)外部抗(kang)壓的(de)(de)(de)(de)殼層及(ji)艦艇上(shang)焊(han)接部位等[3-8]。Ti80合(he)金(jin)(jin)(jin)(jin)(jin)的(de)(de)(de)(de)力學性(xing)能(neng)受(shou)微觀組織特征的(de)(de)(de)(de)影響很大(da)，例如α和(he)β相的(de)(de)(de)(de)體積分(fen)(fen)數和(he)形(xing)態、晶(jing)粒大(da)小和(he)晶(jing)粒取(qu)向、強(qiang)化沉(chen)淀物(wu)的(de)(de)(de)(de)分(fen)(fen)布[9,10]。其(qi)熱加工過(guo)程(cheng)中(zhong)的(de)(de)(de)(de)組織演(yan)變(bian)與(yu)合(he)金(jin)(jin)(jin)(jin)(jin)成分(fen)(fen)、加工參數（變(bian)形(xing)溫度(du)和(he)應(ying)變(bian)速(su)率）等密切相關[11-20]。

除(chu)此之外，鈦合(he)金的(de)熱加(jia)工過(guo)程中(zhong)存在(zai)等軸(zhou)(zhou)組織(zhi)(zhi)(zhi)(zhi)(zhi)、網(wang)籃組織(zhi)(zhi)(zhi)(zhi)(zhi)、層片組織(zhi)(zhi)(zhi)(zhi)(zhi)等諸多組織(zhi)(zhi)(zhi)(zhi)(zhi)形態。Song等[21]研究(jiu)(jiu)了TA5-A鈦合(he)金，結果表明(ming)在(zai)兩相(xiang)區進(jin)(jin)行(xing)熱加(jia)工，獲得晶粒細小等軸(zhou)(zhou)組織(zhi)(zhi)(zhi)(zhi)(zhi)，具有良好的(de)室溫塑(su)性(xing)(xing)[21]。Zhou教授等[22]的(de)研究(jiu)(jiu)表明(ming)，具有等軸(zhou)(zhou)組織(zhi)(zhi)(zhi)(zhi)(zhi)、網(wang)籃組織(zhi)(zhi)(zhi)(zhi)(zhi)以(yi)及β轉變基(ji)體的(de)混合(he)組織(zhi)(zhi)(zhi)(zhi)(zhi)表現出良好強(qiang)度和塑(su)性(xing)(xing)的(de)綜(zong)合(he)性(xing)(xing)能。因(yin)此，需要建立熱加(jia)工工藝-組織(zhi)(zhi)(zhi)(zhi)(zhi)特征與力(li)學性(xing)(xing)能的(de)關系(xi)，進(jin)(jin)而實(shi)現最佳(jia)的(de)綜(zong)合(he)力(li)學性(xing)(xing)能。

本(ben)研究(jiu)以(yi)Ti80合金為研究(jiu)對象(xiang)，考察(cha)不同(tong)變形溫度和應(ying)(ying)變速(su)率條件下Ti80合金的組(zu)(zu)(zu)織演(yan)化(hua)規律及應(ying)(ying)力-應(ying)(ying)變曲線變化(hua)規律，建立熱加工圖。采用450型異(yi)步(bu)熱軋(ya)試驗軋(ya)機進行(xing)Ti80合金不同(tong)軋(ya)制(zhi)溫度下板材制(zhi)備。考察(cha)Ti80合金熱軋(ya)板材的微觀(guan)組(zu)(zu)(zu)織演(yan)化(hua)規律以(yi)及力學性能，確(que)定不同(tong)微觀(guan)組(zu)(zu)(zu)織對力學性能的影(ying)響及其斷裂行(xing)為，為Ti80合金的最優組(zu)(zu)(zu)織調控提供理論指(zhi)導。

1、實驗

所用材料為Ti80合金（Ti-6Al-3Nb-2Zr-1Mo，質量分數,%,下同）。使用線切割將材料加工為Φ8mm×12mm的圓柱形試樣、50mm×50mm×100mm的塊狀試樣。熱壓縮試驗選擇在Gleeble-3800熱模擬試驗機上進行不同變形溫度（800~1050℃）的熱壓縮試驗；應變速率為0.01、0.1、1、5和10s^-1。熱(re)軋(ya)(ya)試驗(yan)(yan)在450型雙輥異步熱(re)軋(ya)(ya)試驗(yan)(yan)軋(ya)(ya)機上(shang)進行，分(fen)別在軋(ya)(ya)制溫(wen)度(du)950℃、初軋(ya)(ya)溫(wen)度(du)1060℃，終軋(ya)(ya)溫(wen)度(du)950℃、以(yi)及在軋(ya)(ya)制溫(wen)度(du)1060℃進行軋(ya)(ya)制，最(zui)終軋(ya)(ya)制變形量為80%。室溫(wen)拉伸試驗(yan)(yan)在型號為4206-006的(de)10t試驗(yan)(yan)機上(shang)進行。

2、結果與分析

2.1Ti80合金原始組織與(yu)相變點分析

圖(tu)1為(wei)(wei)Ti80合金原始組(zu)織(zhi)SEM照片(pian)(pian)。其組(zu)織(zhi)為(wei)(wei)等軸α相(xiang)和(he)β轉(zhuan)變組(zu)織(zhi)（層片(pian)(pian)狀(zhuang)次生相(xiang)αs以(yi)(yi)及(ji)(ji)層片(pian)(pian)狀(zhuang)β相(xiang)）所組(zu)成(cheng)的(de)以(yi)(yi)β轉(zhuan)變組(zu)織(zhi)為(wei)(wei)基(ji)(ji)體(ti)的(de)雙(shuang)態(tai)組(zu)織(zhi)。圖(tu)中灰色襯度(du)為(wei)(wei)α相(xiang)，亮(liang)白(bai)色襯度(du)為(wei)(wei)β相(xiang)。原始組(zu)織(zhi)中等軸的(de)α相(xiang)與(yu)β轉(zhuan)變基(ji)(ji)體(ti)分布均勻。等軸α相(xiang)晶(jing)粒(li)平(ping)均尺寸為(wei)(wei)10.7μm，占(zhan)比為(wei)(wei)53.9%，β相(xiang)占(zhan)比為(wei)(wei)23.9%，次生相(xiang)αs占(zhan)比為(wei)(wei)21.2%。從圖(tu)1中右側組(zu)織(zhi)照片(pian)(pian)可以(yi)(yi)清晰地觀察到層片(pian)(pian)狀(zhuang)的(de)β相(xiang)以(yi)(yi)及(ji)(ji)次生相(xiang)αs，以(yi)(yi)及(ji)(ji)層片(pian)(pian)狀(zhuang)的(de)β轉(zhuan)變基(ji)(ji)體(ti)。

圖2為(wei)Ti80合(he)金(jin)的(de)DSC曲線，向(xiang)上為(wei)吸熱(re)，向(xiang)下為(wei)放熱(re)，升溫速率為(wei)20℃/min。如箭頭所示為(wei)Ti80合(he)金(jin)的(de)β轉(zhuan)變結束點，最(zui)終確定(ding)該合(he)金(jin)的(de)相變點溫度為(wei)1027℃（±20℃）。表1為(wei)Ti80合(he)金(jin)添(tian)加合(he)金(jin)元(yuan)素(su)以及雜質元(yuan)素(su)的(de)實際含(han)量。

2.2Ti80合金熱變形行(xing)為及加(jia)工圖

圖(tu)3為不同(tong)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)溫度(du)(du)和(he)應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)下(xia)(xia)(xia)Ti80合金的(de)(de)(de)應(ying)(ying)力(li)-應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)曲(qu)線、加(jia)(jia)(jia)(jia)(jia)工硬化(hua)(hua)曲(qu)線和(he)峰值(zhi)應(ying)(ying)力(li)。如(ru)圖(tu)3所(suo)示，在應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)相(xiang)同(tong)的(de)(de)(de)條件下(xia)(xia)(xia)，溫度(du)(du)越高(gao)，其(qi)(qi)(qi)(qi)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)抗(kang)力(li)越小。在溫度(du)(du)較低時，材料(liao)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)時其(qi)(qi)(qi)(qi)流變(bian)(bian)(bian)(bian)(bian)應(ying)(ying)力(li)急劇增(zeng)(zeng)(zeng)高(gao)達到(dao)峰值(zhi)應(ying)(ying)力(li)后緩(huan)慢降低，其(qi)(qi)(qi)(qi)曲(qu)線具有(you)典(dian)型(xing)的(de)(de)(de)動(dong)(dong)態再結晶(jing)特征[23]。其(qi)(qi)(qi)(qi)原因(yin)是在變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)階段初期，位(wei)錯(cuo)密(mi)度(du)(du)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)速度(du)(du)快，需要較高(gao)的(de)(de)(de)能(neng)量來啟動(dong)(dong)位(wei)錯(cuo)，引起了(le)應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)硬化(hua)(hua)。而(er)位(wei)錯(cuo)的(de)(de)(de)交滑(hua)移和(he)攀(pan)(pan)移等(deng)引起的(de)(de)(de)軟化(hua)(hua)作用(yong)不足以補償位(wei)錯(cuo)密(mi)度(du)(du)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)帶來的(de)(de)(de)硬化(hua)(hua)。因(yin)此，流動(dong)(dong)應(ying)(ying)力(li)以較快的(de)(de)(de)速度(du)(du)增(zeng)(zeng)(zeng)大(da)，出現峰值(zhi)。隨(sui)著應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)的(de)(de)(de)繼續增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)，材料(liao)中(zhong)(zhong)積累了(le)較多的(de)(de)(de)畸變(bian)(bian)(bian)(bian)(bian)能(neng)開始(shi)發(fa)生動(dong)(dong)態再結晶(jing)。與此同(tong)時，隨(sui)著變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)量的(de)(de)(de)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)，材料(liao)中(zhong)(zhong)的(de)(de)(de)空位(wei)濃度(du)(du)也會(hui)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)，這些(xie)因(yin)素都會(hui)引起材料(liao)的(de)(de)(de)軟化(hua)(hua)，軟化(hua)(hua)作用(yong)大(da)于(yu)硬化(hua)(hua)作用(yong)在應(ying)(ying)力(li)-應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)曲(qu)線上表現為應(ying)(ying)力(li)緩(huan)慢下(xia)(xia)(xia)降。當(dang)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)溫度(du)(du)為950℃及以上時，材料(liao)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)時其(qi)(qi)(qi)(qi)流變(bian)(bian)(bian)(bian)(bian)應(ying)(ying)力(li)增(zeng)(zeng)(zeng)高(gao)到(dao)某一數值(zhi)后基本保持不變(bian)(bian)(bian)(bian)(bian)，具有(you)典(dian)型(xing)的(de)(de)(de)回復特征[23]，其(qi)(qi)(qi)(qi)原因(yin)主要與螺型(xing)位(wei)錯(cuo)的(de)(de)(de)交滑(hua)移和(he)與擴散有(you)關(guan)(guan)的(de)(de)(de)刃型(xing)位(wei)錯(cuo)的(de)(de)(de)攀(pan)(pan)移有(you)關(guan)(guan)。如(ru)圖(tu)3中(zhong)(zhong)顯示了(le)不同(tong)應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)以及變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)溫度(du)(du)下(xia)(xia)(xia)材料(liao)的(de)(de)(de)加(jia)(jia)(jia)(jia)(jia)工硬化(hua)(hua)率(lv)，觀察到(dao)加(jia)(jia)(jia)(jia)(jia)工硬化(hua)(hua)率(lv)隨(sui)應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)的(de)(de)(de)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)而(er)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)，隨(sui)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)溫度(du)(du)的(de)(de)(de)升高(gao)而(er)減小，表明(ming)材料(liao)的(de)(de)(de)加(jia)(jia)(jia)(jia)(jia)工硬化(hua)(hua)率(lv)對(dui)溫度(du)(du)以及應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)敏感。圖(tu)3f顯示了(le)不同(tong)條件下(xia)(xia)(xia)材料(liao)的(de)(de)(de)峰值(zhi)應(ying)(ying)力(li)。可以明(ming)顯看出，峰值(zhi)應(ying)(ying)力(li)隨(sui)應(ying)(ying)變(bian)(bian)(bian)(bian)(bian)速率(lv)的(de)(de)(de)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)而(er)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)，隨(sui)變(bian)(bian)(bian)(bian)(bian)形(xing)(xing)溫度(du)(du)的(de)(de)(de)增(zeng)(zeng)(zeng)加(jia)(jia)(jia)(jia)(jia)而(er)減小。

其(qi)峰值應(ying)(ying)(ying)(ying)力(li)所(suo)對應(ying)(ying)(ying)(ying)的(de)(de)(de)應(ying)(ying)(ying)(ying)變(bian)(bian)量(liang)也隨峰值應(ying)(ying)(ying)(ying)力(li)的(de)(de)(de)降低而(er)(er)減小，這可以反映動(dong)(dong)態再結(jie)晶(jing)(jing)的(de)(de)(de)臨界(jie)(jie)應(ying)(ying)(ying)(ying)變(bian)(bian)隨溫(wen)度(du)(du)(du)的(de)(de)(de)升(sheng)高而(er)(er)向(xiang)低應(ying)(ying)(ying)(ying)變(bian)(bian)移動(dong)(dong)，隨應(ying)(ying)(ying)(ying)變(bian)(bian)速率(lv)的(de)(de)(de)增(zeng)加(jia)而(er)(er)向(xiang)高應(ying)(ying)(ying)(ying)變(bian)(bian)移動(dong)(dong)[24]。變(bian)(bian)形(xing)(xing)速率(lv)越(yue)小，材(cai)料內部(bu)的(de)(de)(de)位錯網絡(luo)有充分的(de)(de)(de)時(shi)間解(jie)離、拆散(san)、轉移形(xing)(xing)成大(da)角度(du)(du)(du)晶(jing)(jing)界(jie)(jie)，進(jin)而(er)(er)形(xing)(xing)成再結(jie)晶(jing)(jing)晶(jing)(jing)核。當應(ying)(ying)(ying)(ying)變(bian)(bian)速率(lv)較大(da)時(shi)，只有通過加(jia)大(da)變(bian)(bian)形(xing)(xing)量(liang)才能促進(jin)位錯的(de)(de)(de)運動(dong)(dong)，實(shi)現再結(jie)晶(jing)(jing)晶(jing)(jing)核的(de)(de)(de)形(xing)(xing)成，再結(jie)晶(jing)(jing)臨界(jie)(jie)應(ying)(ying)(ying)(ying)變(bian)(bian)向(xiang)更高的(de)(de)(de)應(ying)(ying)(ying)(ying)變(bian)(bian)移動(dong)(dong)[23]。另外，在相變(bian)(bian)點附(fu)近存在較低的(de)(de)(de)峰值應(ying)(ying)(ying)(ying)力(li)，特別是在變(bian)(bian)形(xing)(xing)溫(wen)度(du)(du)(du)超過900℃時(shi)，材(cai)料的(de)(de)(de)峰值應(ying)(ying)(ying)(ying)力(li)存在大(da)幅度(du)(du)(du)降低的(de)(de)(de)情(qing)況。

在應變速率為0.01s^-1時，其峰值應力從900℃的51MPa降低到950℃的26MPa，在應變速率為10s^-1時，其峰值應力從900℃的(de)256MPa降(jiang)低到(dao)950℃的(de)126MPa，進一步(bu)表明變形溫度對Ti80合金的(de)變形抗力有很大(da)的(de)影響。

依據動態材料模型DMM建立了TI80合金的熱加工圖，圖4為Ti80合金在應變ε=0.2和ε=0.6的熱加工圖。應變為0.2~0.6時的熱加工圖的輪廓變化不大，并且2種應變的功率耗散值分布情況和大小基本一致。從圖中看其功率耗散系數η的變化范圍很大（8%~65%）；η最大值出現在變形溫度800和1000℃、應變速率0.01~0.1s^-1區域；η最小值出現在高應變速率800~970℃、應變速率0.1~1s^-1區(qu)(qu)(qu)(qu)(qu)域(yu)。穩(wen)定(ding)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)為(wei)加工(gong)圖(tu)中(zhong)(zhong)失穩(wen)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)以外(wai)的(de)(de)部分。在(zai)(zai)(zai)加工(gong)圖(tu)中(zhong)(zhong)，η值(zhi)(zhi)(zhi)較(jiao)高(gao)的(de)(de)區(qu)(qu)(qu)(qu)(qu)域(yu)一(yi)般對(dui)應(ying)動態(tai)再結晶、動態(tai)回復和超塑性變(bian)(bian)(bian)(bian)形(xing)等穩(wen)定(ding)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)，η值(zhi)(zhi)(zhi)越大，表明(ming)用于組織演變(bian)(bian)(bian)(bian)的(de)(de)功(gong)(gong)率(lv)耗散越多，材料的(de)(de)可加工(gong)性就越好，η值(zhi)(zhi)(zhi)較(jiao)高(gao)的(de)(de)區(qu)(qu)(qu)(qu)(qu)域(yu)往往對(dui)應(ying)著最(zui)佳(jia)的(de)(de)加工(gong)性能。但是(shi)，材料的(de)(de)可加工(gong)性能并不(bu)是(shi)嚴格的(de)(de)依(yi)賴于功(gong)(gong)率(lv)耗散系數(shu)，因(yin)為(wei)在(zai)(zai)(zai)加工(gong)失穩(wen)區(qu)(qu)(qu)(qu)(qu)功(gong)(gong)率(lv)耗散系數(shu)也可能會很高(gao)，如(ru)(ru)圖(tu)4a的(de)(de)區(qu)(qu)(qu)(qu)(qu)域(yu)Ⅳ和圖(tu)4b的(de)(de)區(qu)(qu)(qu)(qu)(qu)域(yu)Ⅴ。圖(tu)4a熱(re)加工(gong)圖(tu)穩(wen)定(ding)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)中(zhong)(zhong)顯示(shi)出2個(ge)峰(feng)值(zhi)(zhi)(zhi)η區(qu)(qu)(qu)(qu)(qu)域(yu)，1個(ge)在(zai)(zai)(zai)α+β兩相(xiang)(xiang)區(qu)(qu)(qu)(qu)(qu)，另(ling)1個(ge)跨越β相(xiang)(xiang)變(bian)(bian)(bian)(bian)點，具體位置如(ru)(ru)圖(tu)4a所(suo)示(shi)。圖(tu)4b熱(re)加工(gong)圖(tu)穩(wen)定(ding)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)中(zhong)(zhong)顯示(shi)出3個(ge)峰(feng)值(zhi)(zhi)(zhi)η區(qu)(qu)(qu)(qu)(qu)域(yu)，1個(ge)在(zai)(zai)(zai)α+β兩相(xiang)(xiang)區(qu)(qu)(qu)(qu)(qu)，1個(ge)跨越β相(xiang)(xiang)變(bian)(bian)(bian)(bian)點，最(zui)后1個(ge)在(zai)(zai)(zai)β單相(xiang)(xiang)區(qu)(qu)(qu)(qu)(qu)，具體如(ru)(ru)圖(tu)4b所(suo)示(shi)。其峰(feng)值(zhi)(zhi)(zhi)區(qu)(qu)(qu)(qu)(qu)域(yu)都在(zai)(zai)(zai)低的(de)(de)應(ying)變(bian)(bian)(bian)(bian)速率(lv)范圍(wei)出現0.55以上的(de)(de)η值(zhi)(zhi)(zhi)，在(zai)(zai)(zai)該區(qu)(qu)(qu)(qu)(qu)域(yu)適宜(yi)熱(re)加工(gong)。Ti80合金應(ying)選擇在(zai)(zai)(zai)溫度800~920℃、920~1050℃、應(ying)變(bian)(bian)(bian)(bian)速率(lv)0.01~0.1s-1范圍(wei)內(nei)變(bian)(bian)(bian)(bian)形(xing)，此時功(gong)(gong)率(lv)耗散值(zhi)(zhi)(zhi)大于0.55，為(wei)Ti80合金最(zui)佳(jia)的(de)(de)穩(wen)定(ding)變(bian)(bian)(bian)(bian)形(xing)區(qu)(qu)(qu)(qu)(qu)。

2.3Ti80合金熱變形過程(cheng)的微觀(guan)組織演化規律分析

圖5為(wei)Ti80合(he)金不(bu)同(tong)應變(bian)(bian)速率(lv)和(he)不(bu)同(tong)變(bian)(bian)形溫度下(xia)(xia)的(de)微觀組織。橫(heng)向為(wei)Ti80合(he)金不(bu)同(tong)應變(bian)(bian)速條(tiao)(tiao)件(jian)下(xia)(xia)的(de)微觀組織變(bian)(bian)化(hua)，縱向為(wei)Ti80合(he)金不(bu)同(tong)變(bian)(bian)形溫度條(tiao)(tiao)件(jian)下(xia)(xia)的(de)微觀組織變(bian)(bian)化(hua)。較(jiao)低的(de)變(bian)(bian)形溫度條(tiao)(tiao)件(jian)下(xia)(xia)或者(zhe)接近(jin)相(xiang)變(bian)(bian)點(dian)附(fu)近(jin)較(jiao)高(gao)(gao)的(de)應變(bian)(bian)速率(lv)條(tiao)(tiao)件(jian)下(xia)(xia)，等(deng)軸(zhou)α相(xiang)都可以穩定存在。變(bian)(bian)形溫度較(jiao)高(gao)(gao)時，微觀組織中的(de)等(deng)軸(zhou)α相(xiang)完全轉變(bian)(bian)為(wei)β相(xiang)。在較(jiao)低應變(bian)(bian)速率(lv)條(tiao)(tiao)件(jian)下(xia)(xia)，β相(xiang)晶(jing)粒粗大，晶(jing)界(jie)附(fu)近(jin)富集(ji)的(de)α較(jiao)少(shao)，高(gao)(gao)應變(bian)(bian)速率(lv)條(tiao)(tiao)件(jian)下(xia)(xia)，β晶(jing)粒尺寸明顯減小，晶(jing)粒內α集(ji)束增多。

變形溫度為800℃時，隨著應變速率的增加等軸α相的形態也發生明顯變化。應變速率為10s^-1時，等軸α相晶粒晶界明顯，并且晶粒多為蠕蟲狀。變形溫度為900℃、應變速率0.01s^-1時，等軸α相晶粒形態存在大塊狀、蠕蟲狀以及小顆粒狀晶粒尺寸差別大，其原因為應變速率低，變形時間長，等軸α相部分溶解，β轉變基體分數增大[25]。β轉變基體中部分次生αs聚集由層片狀轉變為塊狀以及球狀，基體中層片狀的β相體積分數減少[26]。隨著應變速率的升高，Ti80合金的組織中等軸α相體積分數先增加后減少，形態轉變為等軸狀，晶粒尺寸持續減小。β轉變基體中β相體積分數增加，應變速率越高，β相體積分數越多。變形溫度950℃、應變速率0.01s^-1時，由于應變速率低，變形過程持續時間長，等軸α相溶解形成β晶粒且其晶粒中存在大量的次生的αs相，晶界附近也富集大量的α相。根據有關學者的研究，對于鈦合金在兩相區保溫時間主要影響次生相αs體積分數及β轉變基體的形態以及體積分數[25]。隨著應變速率的升高，組織中等軸α相體積分數呈現先升高后降低的趨勢。由圖2的DSC曲線表明，在958℃時已經開始存在α相向β相的轉變，溫度越高轉變的體積分數越大。當溫度為1000℃，應變速率為0.01s^-1時，其溫度已經處于β相變點附近，變形時間較長，最終組織為粗大的β相組織。隨著應變速率的升高，β相晶粒尺寸不斷減小，在應變速率為1s^-1時，微觀組織中出現α相并以層片狀存在于β晶粒中。當應變速率增加到10s^-1時，其應變(bian)(bian)速(su)率(lv)快(kuai)，組織轉(zhuan)變(bian)(bian)不完全，微觀組織中(zhong)(zhong)存在較(jiao)少體(ti)積(ji)分數(shu)的(de)等(deng)軸α相晶(jing)(jing)(jing)粒(li)，β晶(jing)(jing)(jing)粒(li)內部為層(ceng)(ceng)片結構，次生(sheng)的(de)層(ceng)(ceng)片狀(zhuang)αs粗(cu)大(da)，層(ceng)(ceng)片間為β相，晶(jing)(jing)(jing)界附近富集大(da)量的(de)α相。當變(bian)(bian)形溫度升(sheng)高到1050℃時，隨著應變(bian)(bian)速(su)率(lv)的(de)增加，組織由粗(cu)大(da)的(de)β相晶(jing)(jing)(jing)粒(li)逐漸(jian)轉(zhuan)變(bian)(bian)為層(ceng)(ceng)片組織，其晶(jing)(jing)(jing)粒(li)為長(chang)條狀(zhuang)晶(jing)(jing)(jing)粒(li)中(zhong)(zhong)存在大(da)量縱橫交錯的(de)α集束。

圖6為(wei)Ti80合(he)金(jin)在(zai)(zai)應(ying)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)速率為(wei)0.1s-1條件下相(xiang)(xiang)(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)點(dian)附近的(de)(de)(de)(de)(de)(de)微觀(guan)(guan)組織形(xing)(xing)(xing)貌(mao)。其中(zhong)圖6a、6b、6c為(wei)光(guang)學顯(xian)微鏡照(zhao)片，圖6a1、6b1、6c1為(wei)掃描電鏡組織照(zhao)片。在(zai)(zai)800℃時(shi)，通(tong)過金(jin)相(xiang)(xiang)(xiang)(xiang)(xiang)照(zhao)片觀(guan)(guan)察可以看到其微觀(guan)(guan)組織為(wei)等(deng)軸(zhou)組織，由(you)等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)和β轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)基(ji)體(ti)組成(cheng)(cheng)。相(xiang)(xiang)(xiang)(xiang)(xiang)較于原始(shi)組織其α相(xiang)(xiang)(xiang)(xiang)(xiang)晶(jing)(jing)(jing)粒(li)大小(xiao)均勻(yun)(yun)，無(wu)明(ming)顯(xian)的(de)(de)(de)(de)(de)(de)方(fang)向性，β轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)基(ji)體(ti)中(zhong)存在(zai)(zai)均勻(yun)(yun)分(fen)(fen)(fen)布的(de)(de)(de)(de)(de)(de)層片狀(zhuang)(zhuang)(zhuang)(zhuang)的(de)(de)(de)(de)(de)(de)次生αs相(xiang)(xiang)(xiang)(xiang)(xiang)。在(zai)(zai)950℃時(shi)組織為(wei)雙態組織，其中(zhong)等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)形(xing)(xing)(xing)態發(fa)生變(bian)(bian)(bian)(bian)(bian)(bian)(bian)化(hua)(hua)(hua)，有不規(gui)則(ze)塊狀(zhuang)(zhuang)(zhuang)(zhuang)、橢(tuo)圓狀(zhuang)(zhuang)(zhuang)(zhuang)和蠕蟲狀(zhuang)(zhuang)(zhuang)(zhuang)。等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)積分(fen)(fen)(fen)數明(ming)顯(xian)減少，晶(jing)(jing)(jing)粒(li)尺寸不均勻(yun)(yun)。β轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)基(ji)體(ti)形(xing)(xing)(xing)態發(fa)生變(bian)(bian)(bian)(bian)(bian)(bian)(bian)化(hua)(hua)(hua)，β轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)基(ji)體(ti)內部(bu)出(chu)現部(bu)分(fen)(fen)(fen)αs相(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)形(xing)(xing)(xing)態由(you)層片狀(zhuang)(zhuang)(zhuang)(zhuang)球(qiu)化(hua)(hua)(hua)為(wei)小(xiao)顆粒(li)狀(zhuang)(zhuang)(zhuang)(zhuang)[27]。當(dang)溫(wen)度(du)升高到1050℃時(shi)，等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)為(wei)β相(xiang)(xiang)(xiang)(xiang)(xiang)，β晶(jing)(jing)(jing)粒(li)為(wei)等(deng)軸(zhou)狀(zhuang)(zhuang)(zhuang)(zhuang)且晶(jing)(jing)(jing)粒(li)大小(xiao)急劇增大，晶(jing)(jing)(jing)粒(li)內部(bu)存在(zai)(zai)沿晶(jing)(jing)(jing)界(jie)向晶(jing)(jing)(jing)內平行(xing)生長的(de)(de)(de)(de)(de)(de)α集束。變(bian)(bian)(bian)(bian)(bian)(bian)(bian)形(xing)(xing)(xing)溫(wen)度(du)對Ti80合(he)金(jin)的(de)(de)(de)(de)(de)(de)微觀(guan)(guan)組織演化(hua)(hua)(hua)有很大的(de)(de)(de)(de)(de)(de)影(ying)響，變(bian)(bian)(bian)(bian)(bian)(bian)(bian)形(xing)(xing)(xing)溫(wen)度(du)在(zai)(zai)950℃（相(xiang)(xiang)(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)點(dian)下）時(shi)，隨著溫(wen)度(du)的(de)(de)(de)(de)(de)(de)升高Ti80合(he)金(jin)α相(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)積分(fen)(fen)(fen)數增大，當(dang)溫(wen)度(du)升高到1050℃（相(xiang)(xiang)(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)點(dian)上）時(shi)，等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)完全(quan)消(xiao)失轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)為(wei)β相(xiang)(xiang)(xiang)(xiang)(xiang)。在(zai)(zai)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)形(xing)(xing)(xing)溫(wen)度(du)由(you)800℃逐漸增加到1050℃時(shi)，其微觀(guan)(guan)組織中(zhong)β轉(zhuan)(zhuan)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)基(ji)體(ti)形(xing)(xing)(xing)態也發(fa)生了明(ming)顯(xian)的(de)(de)(de)(de)(de)(de)變(bian)(bian)(bian)(bian)(bian)(bian)(bian)化(hua)(hua)(hua)，其β相(xiang)(xiang)(xiang)(xiang)(xiang)由(you)開始(shi)的(de)(de)(de)(de)(de)(de)層片狀(zhuang)(zhuang)(zhuang)(zhuang)到細層片狀(zhuang)(zhuang)(zhuang)(zhuang)直到等(deng)軸(zhou)α相(xiang)(xiang)(xiang)(xiang)(xiang)完全(quan)溶解消(xiao)失。次生的(de)(de)(de)(de)(de)(de)αs相(xiang)(xiang)(xiang)(xiang)(xiang)也由(you)一開始(shi)的(de)(de)(de)(de)(de)(de)層片狀(zhuang)(zhuang)(zhuang)(zhuang)到針狀(zhuang)(zhuang)(zhuang)(zhuang)最后為(wei)在(zai)(zai)β晶(jing)(jing)(jing)粒(li)中(zhong)形(xing)(xing)(xing)成(cheng)(cheng)α集束。

圖7為Ti80合金在變形溫度為900℃不同應變速率的微觀組織。當應變速率為10s^-1時，其組織為雙態組織，其中等軸的α相晶粒大小均勻。在部分α相晶粒中可以明顯看到有斷裂現象存在。應變速率降低到0.1s^-1時，材料中α相以及β相分布更加均勻，β轉變組織中的層片更加細小。應變速率為0.01s^-1時，等軸的α相晶粒尺寸略微長大。在900℃時，應變速率對等軸α相晶粒的大小以及均勻性影響較小，但是對β轉變基體的形態影響較大[25]。當應變速率為0.01s^-1時，β轉變基體中β相為塊狀，次生的α相(αs)呈細針狀分布其中。當應變速率增加到0.1s^-1時，β轉變基體仍為塊狀，αs的形態發生改變，其形態由細針狀轉變為小顆粒狀和板條狀均勻地分布在β轉變基體中。當應變速率達到10s^-1時，β轉(zhuan)變(bian)基(ji)體的形(xing)態轉(zhuan)變(bian)為層片狀，αs以及(ji)β相基(ji)本相間(jian)分布。

綜上所述，材料的加工工藝(yi)參數決定材料的微(wei)觀組織，變(bian)形(xing)溫(wen)度和變(bian)形(xing)速率的不(bu)同最終影響材料的微(wei)觀組織如α/β相(xiang)比例，等軸α相(xiang)的晶粒大小以及(ji)形(xing)態(tai)，β轉變(bian)基體(ti)中(zhong)β相(xiang)和αs的相(xiang)比例、分布(bu)以及(ji)形(xing)態(tai)等。

2.4Ti80合(he)金不同熱軋下(xia)的組織演化及(ji)力(li)學(xue)性能

根據(ju)上述獲(huo)得(de)(de)Ti80熱加工圖(tu)以及現(xian)有(you)(you)文獻(xian)，該合(he)(he)金(jin)的(de)(de)(de)(de)(de)微觀組(zu)(zu)(zu)(zu)織(zhi)隨(sui)著變(bian)(bian)(bian)形溫(wen)度變(bian)(bian)(bian)化經(jing)歷從α相轉(zhuan)變(bian)(bian)(bian)為β相、從等(deng)(deng)軸組(zu)(zu)(zu)(zu)織(zhi)轉(zhuan)變(bian)(bian)(bian)為層片組(zu)(zu)(zu)(zu)織(zhi)的(de)(de)(de)(de)(de)變(bian)(bian)(bian)化規律(lv)[10,21,22]。同(tong)時(shi)，文獻(xian)分析說明在等(deng)(deng)軸、網籃(lan)、β轉(zhuan)變(bian)(bian)(bian)基體同(tong)時(shi)存在的(de)(de)(de)(de)(de)情況下對材(cai)料的(de)(de)(de)(de)(de)力學性能(neng)具有(you)(you)不(bu)同(tong)的(de)(de)(de)(de)(de)影(ying)響。Zhou教授(shou)等(deng)(deng)[22]根據(ju)近β鍛造獲(huo)得(de)(de)三(san)態組(zu)(zu)(zu)(zu)織(zhi)屬(shu)于等(deng)(deng)軸、網籃(lan)、β轉(zhuan)變(bian)(bian)(bian)基體的(de)(de)(de)(de)(de)混合(he)(he)組(zu)(zu)(zu)(zu)織(zhi)，實現(xian)了(le)良好的(de)(de)(de)(de)(de)強度和塑(su)性綜(zong)合(he)(he)性能(neng)。因此，通過(guo)熱加工圖(tu)所(suo)確(que)定(ding)的(de)(de)(de)(de)(de)穩定(ding)變(bian)(bian)(bian)形區、熱模擬組(zu)(zu)(zu)(zu)織(zhi)演化過(guo)程以及β轉(zhuan)變(bian)(bian)(bian)點(dian)綜(zong)合(he)(he)考慮，為了(le)獲(huo)得(de)(de)表面質量良好的(de)(de)(de)(de)(de)板材(cai)同(tong)時(shi)控(kong)制(zhi)Ti80合(he)(he)金(jin)的(de)(de)(de)(de)(de)組(zu)(zu)(zu)(zu)織(zhi)演化，確(que)定(ding)本實驗圍繞相變(bian)(bian)(bian)點(dian)進行熱軋試驗的(de)(de)(de)(de)(de)不(bu)同(tong)變(bian)(bian)(bian)形溫(wen)度。將樣品加熱至1060和950℃，獲(huo)得(de)(de)表面質量良好的(de)(de)(de)(de)(de)板材(cai)同(tong)時(shi)控(kong)制(zhi)Ti80合(he)(he)金(jin)的(de)(de)(de)(de)(de)組(zu)(zu)(zu)(zu)織(zhi)演化。

圖(tu)8為(wei)Ti80合金(jin)(jin)不(bu)同軋(ya)(ya)制(zhi)(zhi)狀態(tai)板(ban)材的微觀(guan)組織(zhi)。圖(tu)8a為(wei)軋(ya)(ya)制(zhi)(zhi)溫(wen)度950℃的Ti80合金(jin)(jin)板(ban)材微觀(guan)組織(zhi)，顯示為(wei)雙態(tai)組織(zhi)，其(qi)(qi)晶(jing)(jing)粒(li)較小，組織(zhi)穩定，晶(jing)(jing)粒(li)大小以(yi)及(ji)(ji)分(fen)(fen)布均(jun)勻。另外，其(qi)(qi)等(deng)(deng)軸(zhou)(zhou)α相(xiang)數量(liang)(liang)明(ming)顯減(jian)少，β轉變(bian)組織(zhi)數量(liang)(liang)增(zeng)多，層片狀的β轉變(bian)組織(zhi)中αs明(ming)顯增(zeng)多。在(zai)(zai)(zai)圖(tu)8b中，當初(chu)軋(ya)(ya)溫(wen)度為(wei)1060℃，終(zhong)軋(ya)(ya)溫(wen)度950℃，其(qi)(qi)中在(zai)(zai)(zai)β單相(xiang)區(qu)進行的兩道次熱軋(ya)(ya)變(bian)形(xing)率(lv)分(fen)(fen)別為(wei)24%和28.9%，在(zai)(zai)(zai)兩相(xiang)區(qu)進行2道次熱軋(ya)(ya)，其(qi)(qi)變(bian)形(xing)率(lv)分(fen)(fen)別為(wei)33.3%和44.4%。由于在(zai)(zai)(zai)1060℃保溫(wen)得(de)到(dao)粗大的β晶(jing)(jing)粒(li)，軋(ya)(ya)制(zhi)(zhi)時(shi)β晶(jing)(jing)粒(li)首先沿軋(ya)(ya)制(zhi)(zhi)方向伸長(chang)，當變(bian)形(xing)量(liang)(liang)繼續增(zeng)加達到(dao)再(zai)結晶(jing)(jing)臨界應(ying)變(bian)時(shi),開始(shi)發生動(dong)態(tai)再(zai)結晶(jing)(jing)形(xing)成等(deng)(deng)軸(zhou)(zhou)晶(jing)(jing)粒(li)，隨后(hou)冷卻到(dao)兩相(xiang)區(qu)的過程(cheng)中發生層片狀α相(xiang)的析出，在(zai)(zai)(zai)兩相(xiang)區(qu)軋(ya)(ya)制(zhi)(zhi)時(shi)使晶(jing)(jing)粒(li)晶(jing)(jing)界破碎最終(zhong)形(xing)成網籃(lan)組織(zhi)[27,28]。組織(zhi)有大量(liang)(liang)交錯縱橫的α集(ji)束以(yi)及(ji)(ji)少量(liang)(liang)塊(kuai)狀α相(xiang)。圖(tu)8c為(wei)軋(ya)(ya)制(zhi)(zhi)溫(wen)度在(zai)(zai)(zai)1060℃的組織(zhi)特征(zheng)，其(qi)(qi)初(chu)始(shi)組織(zhi)為(wei)全層片組織(zhi)。因軋(ya)(ya)制(zhi)(zhi)后(hou)冷卻方式為(wei)空冷，冷速快，最后(hou)Ti80合金(jin)(jin)的微觀(guan)組織(zhi)為(wei)長(chang)晶(jing)(jing)粒(li)，晶(jing)(jing)粒(li)中存在(zai)(zai)(zai)大量(liang)(liang)交錯縱橫的α集(ji)束。

一(yi)般來說，鈦(tai)合(he)(he)(he)金等(deng)軸組織(zhi)(zhi)具有(you)良(liang)好(hao)的(de)(de)(de)(de)(de)(de)塑(su)性(xing)(xing)和抗(kang)疲(pi)勞強度，而網(wang)籃組織(zhi)(zhi)往(wang)往(wang)具有(you)高的(de)(de)(de)(de)(de)(de)斷裂韌性(xing)(xing)、優(you)異的(de)(de)(de)(de)(de)(de)抗(kang)疲(pi)勞裂紋(wen)擴展性(xing)(xing)能(neng)。通過初(chu)軋(ya)1060℃，終軋(ya)950℃的(de)(de)(de)(de)(de)(de)軋(ya)制(zhi)(zhi)工藝獲得的(de)(de)(de)(de)(de)(de)網(wang)籃+塊狀α相的(de)(de)(de)(de)(de)(de)混合(he)(he)(he)組織(zhi)(zhi)，綜合(he)(he)(he)了等(deng)軸組織(zhi)(zhi)和網(wang)籃組織(zhi)(zhi)的(de)(de)(de)(de)(de)(de)優(you)異性(xing)(xing)能(neng)，具有(you)高強度和較好(hao)塑(su)性(xing)(xing)的(de)(de)(de)(de)(de)(de)優(you)異綜合(he)(he)(he)力(li)學性(xing)(xing)能(neng)[22]。圖9為(wei)Ti80合(he)(he)(he)金不同熱(re)軋(ya)狀態下的(de)(de)(de)(de)(de)(de)拉(la)伸力(li)學性(xing)(xing)能(neng)。其(qi)中(zhong)試樣(yang)原始(shi)標距(ju)為(wei)50mm的(de)(de)(de)(de)(de)(de)標準棒狀拉(la)伸試樣(yang)。原始(shi)態的(de)(de)(de)(de)(de)(de)室(shi)溫(wen)抗(kang)拉(la)強度最(zui)高，達到944MPa，其(qi)伸長率為(wei)8.05%。在950℃時(shi)軋(ya)制(zhi)(zhi)時(shi)，其(qi)室(shi)溫(wen)抗(kang)拉(la)強度為(wei)736MPa，延(yan)伸率為(wei)12.88%。在1060℃軋(ya)制(zhi)(zhi)時(shi)，其(qi)室(shi)溫(wen)抗(kang)拉(la)強度為(wei)878MPa，延(yan)伸率為(wei)10.88%。而初(chu)軋(ya)溫(wen)度1060℃，終軋(ya)溫(wen)度950℃時(shi)具有(you)最(zui)優(you)的(de)(de)(de)(de)(de)(de)力(li)學性(xing)(xing)能(neng)，其(qi)室(shi)溫(wen)抗(kang)拉(la)強度為(wei)881.6MPa，延(yan)伸率為(wei)11.27%。

在(zai)950℃軋制得到(dao)(dao)的(de)(de)(de)組(zu)(zu)(zu)(zu)織(zhi)(zhi)為雙態組(zu)(zu)(zu)(zu)織(zhi)(zhi)，與(yu)原始組(zu)(zu)(zu)(zu)織(zhi)(zhi)相(xiang)(xiang)比，其(qi)(qi)組(zu)(zu)(zu)(zu)織(zhi)(zhi)中(zhong)(zhong)(zhong)初(chu)生(sheng)的(de)(de)(de)等軸α相(xiang)(xiang)晶粒尺寸減小(xiao)。β轉變(bian)(bian)基(ji)(ji)體(ti)體(ti)積分(fen)數增(zeng)(zeng)加，αs的(de)(de)(de)層(ceng)片更加粗大(da)。對于(yu)雙態組(zu)(zu)(zu)(zu)織(zhi)(zhi)，在(zai)拉(la)伸過(guo)(guo)程(cheng)(cheng)(cheng)中(zhong)(zhong)(zhong)，其(qi)(qi)滑(hua)移(yi)過(guo)(guo)程(cheng)(cheng)(cheng)一開(kai)始是在(zai)個別晶粒中(zhong)(zhong)(zhong)進(jin)行(xing)(xing)，隨著變(bian)(bian)形(xing)程(cheng)(cheng)(cheng)度(du)(du)的(de)(de)(de)增(zeng)(zeng)加，滑(hua)移(yi)將向越來越多的(de)(de)(de)α晶粒中(zhong)(zhong)(zhong)擴(kuo)展并向周圍(wei)的(de)(de)(de)β轉變(bian)(bian)組(zu)(zu)(zu)(zu)織(zhi)(zhi)延伸[22]。由于(yu)β轉變(bian)(bian)基(ji)(ji)體(ti)的(de)(de)(de)數量(liang)，一方(fang)(fang)(fang)(fang)面是層(ceng)片狀的(de)(de)(de)β轉變(bian)(bian)基(ji)(ji)體(ti)對裂紋的(de)(de)(de)阻礙作用(yong)，另一方(fang)(fang)(fang)(fang)面β相(xiang)(xiang)為體(ti)心立方(fang)(fang)(fang)(fang)結構具有(you)12個滑(hua)移(yi)系，滑(hua)移(yi)容易進(jin)行(xing)(xing),可(ke)以有(you)效地提高其(qi)(qi)塑(su)性(xing)。初(chu)軋溫度(du)(du)為1060℃，終軋溫度(du)(du)950℃軋制時，得到(dao)(dao)的(de)(de)(de)組(zu)(zu)(zu)(zu)織(zhi)(zhi)為網籃組(zu)(zu)(zu)(zu)織(zhi)(zhi)，在(zai)其(qi)(qi)微觀(guan)(guan)組(zu)(zu)(zu)(zu)織(zhi)(zhi)中(zhong)(zhong)(zhong)無明顯的(de)(de)(de)晶界，存在(zai)大(da)量(liang)交錯(cuo)縱橫的(de)(de)(de)α集(ji)束(shu)。拉(la)伸時，縱橫交錯(cuo)的(de)(de)(de)α集(ji)束(shu)對裂紋擴(kuo)展有(you)阻礙作用(yong)，組(zu)(zu)(zu)(zu)織(zhi)(zhi)中(zhong)(zhong)(zhong)含有(you)的(de)(de)(de)α相(xiang)(xiang)屬于(yu)密排六方(fang)(fang)(fang)(fang)結構，滑(hua)移(yi)系滑(hua)動困難，材料(liao)的(de)(de)(de)強度(du)(du)升高，塑(su)性(xing)下降[29]。在(zai)軋制溫度(du)(du)為1060℃時，Ti80合金的(de)(de)(de)微觀(guan)(guan)組(zu)(zu)(zu)(zu)織(zhi)(zhi)為全層(ceng)片組(zu)(zu)(zu)(zu)織(zhi)(zhi)。在(zai)其(qi)(qi)微觀(guan)(guan)組(zu)(zu)(zu)(zu)織(zhi)(zhi)中(zhong)(zhong)(zhong)可(ke)以觀(guan)(guan)察到(dao)(dao)明顯的(de)(de)(de)與(yu)軋制方(fang)(fang)(fang)(fang)向平(ping)行(xing)(xing)的(de)(de)(de)長晶粒，晶粒晶界富集(ji)α相(xiang)(xiang)，晶內大(da)量(liang)的(de)(de)(de)α集(ji)束(shu)，其(qi)(qi)α集(ji)束(shu)方(fang)(fang)(fang)(fang)向基(ji)(ji)本與(yu)拉(la)伸方(fang)(fang)(fang)(fang)向成一定的(de)(de)(de)角度(du)(du)（45°~60°），在(zai)拉(la)伸過(guo)(guo)程(cheng)(cheng)(cheng)滑(hua)移(yi)一開(kai)始就(jiu)能穿過(guo)(guo)相(xiang)(xiang)互(hu)平(ping)行(xing)(xing)的(de)(de)(de)α集(ji)束(shu)，并在(zai)晶界α相(xiang)(xiang)處塞(sai)積，引起微區變(bian)(bian)形(xing)不均勻，促進(jin)空(kong)洞的(de)(de)(de)形(xing)成和(he)發展，導致材料(liao)過(guo)(guo)早斷裂，造成塑(su)性(xing)下降[29]。

圖10a、10b、10c分別為不同軋(ya)制條件下Ti80合金(jin)的宏觀拉伸斷(duan)(duan)口照片。可(ke)見，斷(duan)(duan)口的纖維區以及剪切唇(chun)很明(ming)顯，斷(duan)(duan)口呈杯錐(zhui)狀(zhuang)，有明(ming)顯的頸縮現象。

為(wei)(wei)(wei)了進(jin)一(yi)步觀(guan)(guan)(guan)(guan)(guan)察(cha)斷口(kou)(kou)形(xing)(xing)貌(mao)，在放大倍數為(wei)(wei)(wei)2000倍的(de)(de)(de)(de)(de)掃描(miao)電鏡下觀(guan)(guan)(guan)(guan)(guan)察(cha)拉伸試樣，圖(tu)(tu)10a、10a1、10a2分(fen)(fen)別(bie)為(wei)(wei)(wei)在溫度950℃軋制(zhi)宏(hong)觀(guan)(guan)(guan)(guan)(guan)斷口(kou)(kou)形(xing)(xing)貌(mao)、中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)和(he)剪切(qie)(qie)唇微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)。中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)為(wei)(wei)(wei)完全的(de)(de)(de)(de)(de)等軸韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)，由(you)于(yu)晶粒(li)尺寸的(de)(de)(de)(de)(de)不同，韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)的(de)(de)(de)(de)(de)大小也不均勻。中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)還存在大量的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)孔以及微(wei)(wei)(wei)(wei)裂紋。和(he)中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)不同，剪切(qie)(qie)唇的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)由(you)網(wang)狀分(fen)(fen)布的(de)(de)(de)(de)(de)韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)組成，其韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)無論大小和(he)深度都要明(ming)顯次于(yu)中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)。圖(tu)(tu)10b、10b1、10b2分(fen)(fen)別(bie)為(wei)(wei)(wei)初軋溫度為(wei)(wei)(wei)1060℃，終軋溫度為(wei)(wei)(wei)950℃的(de)(de)(de)(de)(de)宏(hong)觀(guan)(guan)(guan)(guan)(guan)斷口(kou)(kou)形(xing)(xing)貌(mao)、中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)和(he)剪切(qie)(qie)唇微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)。頸(jing)(jing)縮(suo)(suo)程度有(you)所下降，中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)可以觀(guan)(guan)(guan)(guan)(guan)察(cha)到大量韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)的(de)(de)(de)(de)(de)存在，同樣存在大量的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)孔，該狀態下的(de)(de)(de)(de)(de)斷裂機制(zhi)為(wei)(wei)(wei)韌(ren)(ren)(ren)(ren)性斷裂[30]。圖(tu)(tu)10c為(wei)(wei)(wei)1060℃軋制(zhi)的(de)(de)(de)(de)(de)宏(hong)觀(guan)(guan)(guan)(guan)(guan)斷口(kou)(kou)，頸(jing)(jing)縮(suo)(suo)程度不明(ming)顯，中(zhong)心(xin)纖(xian)(xian)(xian)維區(qu)(qu)更加粗糙，其剪切(qie)(qie)唇的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)大部分(fen)(fen)為(wei)(wei)(wei)網(wang)狀韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)，在宏(hong)觀(guan)(guan)(guan)(guan)(guan)上表(biao)現為(wei)(wei)(wei)頸(jing)(jing)縮(suo)(suo)小，延(yan)伸率低(di)。3種軋制(zhi)狀態，在宏(hong)觀(guan)(guan)(guan)(guan)(guan)形(xing)(xing)貌(mao)上，其頸(jing)(jing)縮(suo)(suo)從上往下依次減小，其中(zhong)圖(tu)(tu)10a微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)組織(zhi)(zhi)為(wei)(wei)(wei)雙(shuang)態組織(zhi)(zhi)，其頸(jing)(jing)縮(suo)(suo)最(zui)(zui)(zui)大，韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)大而深，延(yan)伸率最(zui)(zui)(zui)佳。圖(tu)(tu)10c的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)組織(zhi)(zhi)為(wei)(wei)(wei)層(ceng)片組織(zhi)(zhi)頸(jing)(jing)縮(suo)(suo)最(zui)(zui)(zui)小，韌(ren)(ren)(ren)(ren)窩(wo)(wo)(wo)小而淺，延(yan)伸率最(zui)(zui)(zui)差。圖(tu)(tu)10b的(de)(de)(de)(de)(de)微(wei)(wei)(wei)(wei)觀(guan)(guan)(guan)(guan)(guan)組織(zhi)(zhi)為(wei)(wei)(wei)網(wang)籃組織(zhi)(zhi)，強度高且延(yan)伸率較高，有(you)良好的(de)(de)(de)(de)(de)綜合力學性能。

3、結論

1)Ti80合金峰值應力隨著變形溫度升高以及應變速率的降低而降低，為典型的溫度以及應變速率敏感型合金。變形初期，隨應變速率的升高，Ti80合金的加工硬化率也不斷升高。根據加工圖分析，Ti80合金的熱加工區間應該選擇在溫度800~920℃、920～1050℃、應變速率0.01~0.1s^-1范圍內變(bian)形，此(ci)時功率耗散值(zhi)大于0.55，為Ti80合金較佳的穩定(ding)變(bian)形區。

2)在900℃之前，Ti80合金熱變形過程隨著變形溫度的升高，等軸的α相體積分數增大，β轉變組織中次生αs形態為小顆粒狀分布在β轉變基體中。相變點以上時，隨著應變速率的升高，β晶粒尺寸會減小，應變速率超過1s^-1時，會有(you)大量α集(ji)束生(sheng)成。

3)結合熱(re)加(jia)工(gong)圖以(yi)及不(bu)同(tong)軋制溫(wen)度的試驗，Ti80合金初軋溫(wen)度為(wei)1060℃，終軋溫(wen)度為(wei)950℃時(shi)獲得(de)最優的力學性能，其組織(zhi)為(wei)網籃組織(zhi)+部分(fen)塊(kuai)狀α相的混合組織(zhi)，室溫(wen)抗拉強度能達(da)到881.6MPa，延伸率為(wei)11.27%。

4)Ti80合金在(zai)950℃軋制時表現出良(liang)好塑(su)性(xing)(xing)，斷口(kou)頸(jing)縮明顯，中(zhong)心(xin)纖維區(qu)的(de)等軸(zhou)韌(ren)(ren)(ren)窩(wo)(wo)明顯，剪(jian)切(qie)唇區(qu)域韌(ren)(ren)(ren)窩(wo)(wo)大而(er)深(shen)，為(wei)典(dian)型的(de)韌(ren)(ren)(ren)性(xing)(xing)斷裂。初(chu)軋溫度(du)為(wei)1060℃，終軋溫度(du)為(wei)950℃時，中(zhong)心(xin)纖維區(qu)韌(ren)(ren)(ren)窩(wo)(wo)有所減小，剪(jian)切(qie)唇區(qu)域為(wei)網(wang)狀韌(ren)(ren)(ren)窩(wo)(wo)，韌(ren)(ren)(ren)窩(wo)(wo)較小，塑(su)性(xing)(xing)有所降低。當軋制溫度(du)為(wei)1060℃時，中(zhong)心(xin)纖維區(qu)以及剪(jian)切(qie)唇區(qu)域的(de)韌(ren)(ren)(ren)窩(wo)(wo)都進一步縮小，特別是剪(jian)切(qie)唇的(de)網(wang)狀韌(ren)(ren)(ren)窩(wo)(wo)小而(er)淺。

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