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多(duo)向鍛造工藝對AZ80鎂合金顯微組(zu)織和力學性能(neng)的影響

文章來源：sjzwx 更新時間：2013-12-28 09:35:36

 多向鍛造工藝對AZ80鎂合金顯微組織和力學性能的影響*摘要通過多向鍛造工藝制備出了組織均勻、晶粒尺寸為1-2um的AZ80鎂合金鍛坯.經7個道次鍛壓，材料硬度、屈服強度和抗拉強度達到最大，分別為87.3HB,258.78MPa和345.04MPa，是鍛前試樣硬度的1.43倍、強度的2倍;伸長率在6個道次達到最大，為7.85%，是鍛前的2.45倍.多向鍛造工藝下，材料內部易形成交錯變形帶，有利于組織細化.形變誘導晶粒細化是主要的晶粒細化機制.晶粒細化過程存在一臨界應變員，當實際應變量‘超過臨界應變最、時，材料基本為動態再結晶細晶組織，進一步細化變得困難.鑄態試樣室溫拉伸斷口為準解理斷裂加少量剪切斷裂，鍛后試樣斷口出現大最細小韌窩.隨應變最的增加，韌窩數目增多，分布趨向均勻，材料延性增大.關鍵詞AZ80鎂合金，多向鍛造，晶粒細化，顯微組織，力學性能晶粒細化是提高Mg及鎂合金綜合性能的重要手段之一通過細化晶粒不僅可以提高材料的強度，還可以改善其塑性和韌性.此外，由于晶界協調變形在鎂合金的塑性變形過程中起著相當重要的作用，而通過晶粒細化可有效提高其晶界協調變形能力.因此，晶粒細化在鎂合金塑性加工中具有非常重要的地位近年來大塑性變形(severeplasticdeformation)方法作為細化晶粒，獲得高性能材料的有效途徑一直廣受關注.其中代表性的方法有等徑角擠(ECAE)、累積疊扎(ARB)、多道次嫩擠、高壓扭轉變形(HPT)和多向鍛造(MPF)等(deng).這些工(gong)(gong)藝方法不僅(jin)能使材(cai)(cai)(cai)料(liao)獲44高(gao)(gao)強度(du)(du)，提(ti)高(gao)(gao)其韌性(xing)(xing)(xing)(xing)和(he)塑(su)性(xing)(xing)(xing)(xing)，甚至還可(ke)使材(cai)(cai)(cai)料(liao)獲得(de)(de)超(chao)塑(su)性(xing)(xing)(xing)(xing)[[2,3].文獻(xian)[4,5」研(yan)究(jiu)表(biao)(biao)明，經ECAE后的(de)(de)(de)(de)鎂(mei)合(he)金(jin)具(ju)有(you)(you)(you)極細(xi)(xi)(xi)的(de)(de)(de)(de)晶(jing)粒(li)(li)(li)(li)結(jie)構并(bing)(bing)表(biao)(biao)現出(chu)與(yu)眾不同的(de)(de)(de)(de)力(li)(li)學(xue)(xue)行(xing)為，如高(gao)(gao)的(de)(de)(de)(de)介朋仗應(ying)(ying)(ying)(ying)力(li)(li)、反常的(de)(de)(de)(de)Hall-Petch關系、大(da)(da)幅(fu)度(du)(du)提(ti)高(gao)(gao)的(de)(de)(de)(de)塑(su)性(xing)(xing)(xing)(xing)以(yi)及低溫超(chao)塑(su)性(xing)(xing)(xing)(xing)和(he)高(gao)(gao)應(ying)(ying)(ying)(ying)變(bian)(bian)(bian)(bian)速率超(chao)塑(su)性(xing)(xing)(xing)(xing)等(deng)特(te)(te)征，其變(bian)(bian)(bian)(bian)形機理(li)也發(fa)生了改變(bian)(bian)(bian)(bian)，一些高(gao)(gao)溫變(bian)(bian)(bian)(bian)形機理(li)，如非(fei)纂(zuan)面滑移(yi)、晶(jing)界滑移(yi)、動態(tai)回(hui)復等(deng)在(zai)室溫下亦叮發(fa)生同.但(dan)該工(gong)(gong)藝目(mu)前還處于(yu)(yu)實驗(yan)室的(de)(de)(de)(de)研(yan)究(jiu)階段，距(ju)離工(gong)(gong)業應(ying)(ying)(ying)(ying)用(yong)還有(you)(you)(you)較大(da)(da)的(de)(de)(de)(de)距(ju)離.反復多(duo)(duo)向(xiang)(xiang)鍛(duan)造(zao)強應(ying)(ying)(ying)(ying)變(bian)(bian)(bian)(bian)工(gong)(gong)藝簡單、成(cheng)本低、使用(yong)現有(you)(you)(you)的(de)(de)(de)(de)工(gong)(gong)業裝備(bei)可(ke)制(zhi)備(bei)大(da)(da)塊致密材(cai)(cai)(cai)料(liao)并(bing)(bing)使材(cai)(cai)(cai)料(liao)性(xing)(xing)(xing)(xing)能得(de)(de)到改善等(deng)優點，有(you)(you)(you)望直接應(ying)(ying)(ying)(ying)用(yong)于(yu)(yu)工(gong)(gong)業化(hua)生產(chan).Belyakov等(deng)[7-9)對多(duo)(duo)晶(jing)純銅和(he)不銹(xiu)鋼在(zai)多(duo)(duo)向(xiang)(xiang)鍛(duan)造(zao)工(gong)(gong)藝下組(zu)(zu)織(zhi)演變(bian)(bian)(bian)(bian)規律進(jin)行(xing)了研(yan)究(jiu)，形變(bian)(bian)(bian)(bian)中外加載荷方向(xiang)(xiang)的(de)(de)(de)(de)變(bian)(bian)(bian)(bian)化(hua)(此為多(duo)(duo)向(xiang)(xiang)鍛(duan)造(zao)工(gong)(gong)藝最顯(xian)著特(te)(te)點)有(you)(you)(you)助于(yu)(yu)形成(cheng)相互交錯(cuo)(cuo)高(gao)(gao)密度(du)(du)位錯(cuo)(cuo)墻，材(cai)(cai)(cai)料(liao)在(zai)低、中等(deng)應(ying)(ying)(ying)(ying)變(bian)(bian)(bian)(bian)卜產(chan)生大(da)(da)量具(ju)有(you)(you)(you)高(gao)(gao)密度(du)(du)位錯(cuo)(cuo)亞(ya)品(pin).隨著應(ying)(ying)(ying)(ying)變(bian)(bian)(bian)(bian)的(de)(de)(de)(de)水積，這些亞(ya)晶(jing)逐漸等(deng)軸化(hua)且位向(xiang)(xiang)差增大(da)(da)，最終形成(cheng)超(chao)細(xi)(xi)(xi)組(zu)(zu)織(zhi).Sitdikov等(deng)!’。一’3!對鑄態(tai)祖品(pin)7475鋁合(he)金(jin)進(jin)行(xing)多(duo)(duo)向(xiang)(xiang)鍛(duan)造(zao)實驗(yan)，發(fa)現變(bian)(bian)(bian)(bian)形過(guo)程(cheng)中品(pin)粒(li)(li)(li)(li)內(nei)部(bu)易形成(cheng)取向(xiang)(xiang)各(ge)異、相互交錯(cuo)(cuo)的(de)(de)(de)(de)變(bian)(bian)(bian)(bian)形帶和(he)微剪切帶，從而(er)引起晶(jing)粒(li)(li)(li)(li)連(lian)續破碎，H[I粒(li)(li)(li)(li)細(xi)(xi)(xi)化(hua)機制(zhi)與(yu)連(lian)續性(xing)(xing)(xing)(xing)動態(tai)再(zai)(zai)(zai)結(jie)晶(jing)相似.文獻(xian)[14-17)對多(duo)(duo)向(xiang)(xiang)反復鍛(duan)造(zao)對7075鋁合(he)金(jin)組(zu)(zu)織(zhi)和(he)性(xing)(xing)(xing)(xing)能的(de)(de)(de)(de)影響(xiang)研(yan)究(jiu)表(biao)(biao)明，材(cai)(cai)(cai)料(liao)鍛(duan)造(zao)過(guo)程(cheng)中發(fa)生完全動態(tai)再(zai)(zai)(zai)結(jie)品(pin)，形成(cheng)平均尺寸小(xiao)于(yu)(yu)25m的(de)(de)(de)(de)細(xi)(xi)(xi)小(xiao)等(deng)軸再(zai)(zai)(zai)結(jie)品(pin)品(pin)粒(li)(li)(li)(li)結(jie)構.鍛(duan)件力(li)(li)學(xue)(xue)性(xing)(xing)(xing)(xing)能得(de)(de)到很大(da)(da)的(de)(de)(de)(de)提(ti)高(gao)(gao).與(yu)高(gao)(gao)層錯(cuo)(cuo)能金(jin)屬相比，鎂(mei)合(he)金(jin)在(zai)熱變(bian)(bian)(bian)(bian)形過(guo)程(cheng)中易發(fa)生動態(tai)再(zai)(zai)(zai)結(jie)晶(jing)(DRX)，由變(bian)(bian)(bian)(bian)形中強應(ying)(ying)(ying)(ying)變(bian)(bian)(bian)(bian)誘發(fa)動態(tai)再(zai)(zai)(zai)結(jie)品(pin)導(dao)致晶(jing)拉細(xi)(xi)(xi)化(hua)的(de)(de)(de)(de)程(cheng)度(du)(du)極高(gao)(gao)118.191.但(dan)目(mu)前有(you)(you)(you)關多(duo)(duo)向(xiang)(xiang)鍛(duan)造(zao)工(gong)(gong)藝對鎂(mei)合(he)金(jin)組(zu)(zu)織(zhi)和(he)性(xing)(xing)(xing)(xing)能的(de)(de)(de)(de)影響(xiang)鮮有(you)(you)(you)報道!20]本文對AZ80鎂(mei)合(he)金(jin)使用(yong)多(duo)(duo)向(xiang)(xiang)反復熱鍛(duan)，品(pin)粒(li)(li)(li)(li)細(xi)(xi)(xi)化(hua)效果好，同時材(cai)(cai)(cai)料(liao)的(de)(de)(de)(de)綜(zong)合(he)力(li)(li)學(xue)(xue)性(xing)(xing)(xing)(xing)能得(de)(de)到較大(da)(da)提(ti)1你