湖北民族学院物化实验报告——二元合金相图.doc

二元合金相图一、目的要求1.用热分析法测绘Pb-Sn二元金属相图。2.了解热分析法的测量技术。二、预习要求1.掌握热分析法测量绘制相图的基本原理。2.熟悉实验仪器的性能及使用方法，了解影响实验测定的各种因素。3.理解步冷曲线的物理意义，掌握如何由实验数据绘制相图的方法。三、基本原理相图是多相(二相或二相相以上)体系处于相平衡状态时体系的某物理性质(如温度)对体系的某一自变量(如组成)作图所得的图形，图中能反映出相平衡情况(相的数目及性质等)，故称为相图。二元或多元体系的相图常以组成为自变量，其物理性质则大多取温度。由于相图能反映出多相平衡体系在不同自变量条什下的相平衡情况，因此，研究多相体系的性质，以及多相体系相平衡情况的演变(例如冶金工业冶炼钢铁或其他合金的过程，石油工业分离产品的过程等)，都要用到相图。图4.1是一种类型的二元简单低共熔物相图。图中A、B表示二个组分的名称，纵轴是物理量温度T，横轴是组分B的百分含量B。在acb线的上方，体系只有一个相(液相)存在；在ecf线以下，体系有两个相(两个固相晶体A、晶体B)存在；在ace所包为的面积中，一个固相(晶体A)和一个液相(A在B中的饱和熔化物)共存；在bcf所包围的面积中，也是一个固相(晶体B)和一个液相(B在A中的饱和熔化物)共存；图中c点是ace与bef两个相区的交点，有三相（晶体A、晶体B、饱和熔化物）共存。测绘相图就是要将相图中这些分隔相区的线画出来。常用的实验方法是热分析法。热分析法所观察的物理性质是被研究体系的温度。将体系加热熔融成一均匀液相，然后让体系缓慢冷却，并每隔一定时间(例如半分钟或一分钟)读体系温度一次，以所得历次温度值对时间作图，得一曲线，通常称为步冷曲线或冷却曲线，图4.2是二元金属体系的一种常见类型的步冷曲线。冷却过程中，若体系发生相变，就伴随着一定热效应，团此步冷曲线的斜率将发生变化而出现转折点，所以这些转折点温度就相当于被测体系在相图中分隔线上的点。若图4.2是图4.1中组成为P的体系的步冷曲线，则点2、3就分别相当于相图中的点G、H。因此，取一系列组成不同的体系，作出它们的步冷曲线，找出各转折点，即能画出二元体系的最简单的相图(对复杂的相图，还必须有其他方法配合，才能画出)。温度温度时间0100B%ABPaecbf12345GH图4.1 A-B体系相图 图4.2 步冷曲线从相图定义可知，用热分析法测绘相图的要点如下： 被测体系必须时时处于或非常接近于相平衡状态。因此，体系冷却时，冷却速度必须足够慢，以保证上述条件近于实现。若体系中的几个相都是固相，这条件通常很难实现(因固相与固相间转化时的相变热较小)，此时测绘相图，常用其它方法(如差热分析法)。 测定时被测体系的组成值必须与原来配制样品时的组成值一致。如果测定过程中样品各处不均匀，或样品发生氧化变质，这一要求就不能实现。 测得的温度值必须能真正反映体系在所测时间时的温度值。因此，测温仪器的热容必须足够小，它与被测体系的热传导必须足够良好，测温探头必须深入到被测体系的足够深度处。 本实验测定铅、锡二元金属体系的相图，用SWKY数字控温仪，通过KWL-08可控升降温电炉来控制体系的加热和冷却速度。四、仪器和药品1.仪器SWKY型数字控温仪一台；KWL-08型可控升降温电炉一台；样品管一只。2.药品铅(CP)；锡(CP)。五、实验步骤1.如图4.3实验装置所示连接实验仪器。冷风机电压表加热器电压表内控外控冷风量调节加热量调节开关电炉SWKY数字控温仪温度传感器图4.3 步冷曲线测量实验装置示意图2.测定被研究体系的步冷曲线 配制样品用感量为0.1克的台称分别配制含锡量为20、40、61.9、80%的铅锡混合物各100克，另外称纯铅100克，纯锡80克，分别放在6个硬质破璃样品管中。 依次测锡、铅以及含锡61.9、80、40、20等样品的步冷曲线。将样品管放在加热电炉中，让样品熔化(在样品上方覆盖一层石墨粉，以防止样品氧化)，加热方法见KWL-08可控升降温电炉使用方法和SWKY数字控温仪操作步骤。样品的温度不宜升得太高，一般在样品全部熔化后，再升高30左右即可(如升得太高，样品易氧化变质，而且将增加冷却时间；如太低，则不能明显地测得转折点)。将KWL-08可控升降温电炉的冷风量调节逆时针旋转到底（最小），加热量调节顺时针旋转到底（最大），“内控”、“外控”开关置于“外控”，电源“开”“关”置于“开”。采用SWKY数字控温仪控温时，由于玻璃试样料管内温度较炉膛内温度的滞后性，故当设置完成进行加热时，必须将温度传感器置于炉膛内。系统需降温时，再将温度传感器置于玻璃试样料管内（注意：当温度离设置温度30左右时，将加热量调节逆时针旋转减少加热电压，降低加热速度）。样品全部熔化后，电源“开”“关”置于“关”，让其缓慢冷却，每隔30秒钟或一分钟记录一次温度，直到步冷曲线的水平部分以下为止。六、实验注意事项1.实验中要注意控制升温熔化和降温冷却的速度。2.每次实验要保证样品完全熔化，熔化完以后还要使温度升高30左右。3.冷却时间要充分，直到温度下降到步冷曲线水平部分以下为止。4.实验中保证样品不被影响物污染。七、数据处理实验数据记录：含锡40%时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）30317.41230213.32430167.73630113.1483084.860313.91260211.32460165.13660112.2486084.390310.11290209.42490162.73690111.3489083.7120306.61320207.62520160.43720110.4492083.21503031350205.82550158.43750109.6495082.7180299.613802042580156.53780108.7498082.1210296.11410202.22610154.63810107.9501081.6240292.81440200.42640152.63840107504081.1270289.41470198.62670150.93870106.2507080.6300285.91500196.92700149.43900105.4510080.1330282.81530195.22730148.23930104.6513079.6360279.61560193.427601473960103.8516079.1390276.41590191.72790145.83990103519078.6420273.216201902820144.64020102.3522078.2450270.11650188.22850143.24050101.5525077.7480267.11680186.62880141.94080100.8528077.2510264.11710184.92910140.54110100.1531076.7540261.31740183.32940139.1414099.3534076.3570258.51770181.62970137.8417098.6537075.9600255.818001803000136.4420097.8540075.4630253.31830178.83030135.1423097.2543075660250.91860178.83060133.8426096.5546074.5690248.61890179.53090132.5429095.8549074.1720246.419201803120131.3432095.5552073.7750244.31950180.23150130.1435094.5555073.2780242.21980180.33180128.9438093.8558072.8810240.12010180.23210127.7441093.2561072.38402382040180.13240126.5444092.55640728702362070179.93270125.4447091.9567071.5900234.12100179.83300124.3450091.3570071.19302322130179.7333012.31453090.7573070.8960230.12160179.53360122.1456090.1576070.3990228.22190179.13390121459089.5579069.91020226.32220178.83420120462088.8-1050224.42250178.33450118.9465088.3-1080222.52280177.63480117.9468087.7-1110220.62310176.83510116.9471087.1-1140218.62340175.43540115.9474086.5-1170216.82370173.33570115477085.9-12002152400170.53600114480085.4-含锡20%时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）30320.71230214.82430149.63630107.1483080.560317.31260212.42460148.13660106.2486079.990313.51290210.12490146.63690105.4489079.4120309.71320207.72520145.33720104.6492078.9150305.91350205.42550144.13750103.8495078.5180302.11380203.22580143.13780103.1498078.1210298.41410200.92610142.13810102.2501077.5240294.61440198.82640141.13840101.4504077.1270291.11470196.72670140.13870100.7507076.5300287.61500194.62700139.1390099.9510075.9330284.11530192.62730137.9393099.2513075.5360281.21560190.62760136.9396098.4516075.1390278.71590188.72790135.7399097.7519074.6420276.51620186.82820134.6402097.1522074.2450274.41650184.92850133.4405096.3525073.7480272.41680183.12880132.2408095.6528073.3510270.51710181.22910131.1411094.9531072.8540268.51740179.42940129.9414094.2534072.4570266.61770177.62970128.8417093.6537071.9600264.81800175.93000127.7420092.9540071.5630263.11830174.23030126.6423092.2543071.1660261.21860176.63060125.5426091.6546070.7690259.31890170.93090124.4429090.9549070.2720257.21920169.33120123.3432090.3552069.8750255.11950167.73150122.2435089.7-780252.81980170.73180121.2438089.1-810250.42010174.23210120.2441088.4-840248.12040173.73240119.2444087.8-870245.52070171.93270118.1447087.2-900242.92100169.83300117.1450086.6-930240.32130167.63330116.1453086.1-960237.72160165.53360115.2456085.5-990235.22190163.43390114.2459084.9-1020232.52220161.53420113.3462084.3-1050229.92250159.63450112.4465083.7-1080227.42280157.73480111.4468083.2-1110224.82310156.13510110.6471082.6-1140222.22340154.33540109.7474082.1-1170219.72370152.73570108.8477081.6-1200217.22400151.13600107.9480081.1-含锡61.9%时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）30293.71230202.82430177.83630111.5483082.660292.61260200.52460176.83660110.6486082.190290.91290198.82490175.13690109.6489081.5120289.213201972520172.63720108.8492081150286.91350195.42550169.53750107.7495080.4180284.61380193.72580166.63780106.9498079.9210282.314101922610163.93810106501079.5240279.91440190.52640161.33840105.2504078.9270277.61470188.926701593870104.3507078.4300274.91500187.42700156.53900103.5510077.9330272.51530185.92730154.23930102.6513077.4360269.91560184.927601523960101.9516076.9390267.11590184.62790149.93990101519076.4420264.31620184.62820147.94020100.3522075.9450261.71650184.32850146.1405099.5525075.5480259.51680183.82880144.3408098.7528075510256.41710183.12910142.6411098531074.5540253.81740182.32940140.8414097.3534074.2570251.21770181.72970139.3417096.5537073.6600248.81800181.43000137.7420095.8540073.2630246.91830181.23030136.1423095.1543071.7660245.51860181.23060134.5426094.4546072.3690241.71890181.13090133.1429093.7549071.972024019201813120131.6432093552071.4750237.31950180.93150130.2435092.4555071780234.31980180.83180128.8438091.7558070.6810231.82010180.83210127.4441091561070.2840229.12040180.63240126.2444090.4564069.8870226.92070180.53270124.9447089.8-900224.72100180.43300123.6450089.1-930222.72130180.23330122.5453088.5-960220.32160180.13360121.2456087.9-990218.42190179.93390120.1459087.2-1020216.32220179.83420118.9462086.6-1050214.52250179.73450117.9465086.1-1080212.62280179.63480116.7468085.4-1110210.12310179.53510115.7471084.9-1140208.22340179.43540114.6474084.3-1170206.12370179.13570113.4477083.7-1200204.42400178.63600112.5480083.2-含锡80%时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）时间/S温度（）30319.21230206.42430178.83630115.8483086.160315.41260204.624601783660114.8486085.690311.81290202.72490176.53690113.8489084.9120308.21320200.925201743720112.9492084.4150304.71350199.12550171.53750112495083.8180301.41380197.32580168.73780111.1498083.32102911410195.826101663810110.2501082.8240287.71440198.32640163.63840109.2504082.2270284.41470201.22670161.33870108.4507081.7300281.41500202.12700159.13900107.5510081.2330278.31530201.92730157.13930106.7513080.7360275.21560202.127601553960105.9516080.2390272.21590200.32790153.13990105519079.7420269.31620199.32820151.34020104.3522079.2450266.41650198.42850149.54050103.5525078.6480263.61680197.32880147.84080102.7528078.2510260.71710196.42910146.14110102531077.7540258.11740195.32940144.54140101.1534077.2570255.41770194.32970142.94170100.4537076.8600252.71800193.43000141.2420099.7540076.3630250.21830192.43030139.8423098.9543075.8660247.61860191.43060138.4426098.3546075.4690245.11890190.43090137429097.5549074.9720242.71920189.33120135.5432096.8552074.5750240.11950188.53150134.1435096.2555074780237.91980187.43180132.8438095.5558073.6810235.52010186.33210131.5441094.8561073.1840233.22040185.33240130.3444094.1564072.68702312070