Current Research Status of Micro-Scale Solidification Models of Binary Alloys

According to determine the non-equilibrium solidification path and local liquid solute concentration in the macro transport model during solidification process of binary alloys, the two kinds of micro-scale solidification models are discussed detailedly, viz. solidification kinetics model and miceosegregation model. The current research status of deterministic solidification kinetics model and semi-analytical microsegregation model are reviewed comprehensively, respectively. The main influencing factors of the two models have also been discussed, viz. undercooling and nucleation rate & back-diffusion and coarsening. Further more, the practical value in the coupled numerical simulation of alloy solidification and the future developmental directions of the micro-scale solidification models are elaborated.     

Prediction of the Leakage of Aluminium Alloy Casting and It''s Prevention

Two aspects of the study on the leakage of aluminium are introduced after the leakage mechanism of aluminium alloy casting is described. Three mathematical models, criteria function models, continuing equations-Darcy's law models, hydrogen diffusion-controlled pore growth models, are studied. Some measures of predicting leakage of casting in practice are summarized, such as the treatment of aluminium liquid and the adoption of new technics, Many different models of pore formation and growth have been proposed, however, each of these models has limitation and is not precision enough. Measures in practice have certain significance to the study of predicting leakage of casting, however, to obtain these measures cost a lot of time, manpower and material resource. In order to predict pore formation and growth of aluminium casting more precision, these mathematical models and practical measures should be integrated felicitously in different condition.     

A RESEARCH OF THE INFLUNCE OF RARE-EARTH ELEMENT ON THE THERMAL FATIGUE BEHAVIOR OF CAST IRON

It is known that cylinder heads, exhaust manifoids, ingot molds, etc. are often failed resulting from thermal fatigue. For this reason, the influence of RE on the thermal fatigue behavior of cast iron was studied by measn of a thermal fatigue test unit with completely constrained strain developed by ourselves. The test results shown that RE can improve the thermal fatigue resistance of cast iron greatly when residual RE contents surpass a critical value. This value is 0.04-0.045% for light Rare-Earth, and 0.045-0.05%; for heavy Rare-Earth. Further more, the relationship between RE and the thermophysical and mechanical properties of cast iron which have influence on thermal fatigue resisteance was also discussed.     

7055铝合金单级时效微观结构演变的透射电镜研究

采用透射电子显微镜对固溶单级时效处理7055铝合金中的沉淀相进行了研究.在较短的时效时间里,可以观察到GP区在[111]面上形成,随着时效时间增加,GP区逐渐长大.η＇亚稳相在120℃时效4 h的时候被发现,它与基体的取向关系是[0 0 0 1]η＇//[1 (1) 1]Al及(1 0 (1) 1)η＇//(1 1 0)Al.在时效达到24 h时,η相便析出,它们与基体存在[(1) 1 0 0]η//[1 1 0]Al及(0 0 0 1)η//(1 1 1)Al的取向关系.由于η＇亚稳相和η相颗粒的密度相比于区而言较小,所以GP区对提高该时效合金的强度和硬度起至关重要的作用.     

DSC法和XRD法测定Ni74Si10B16非晶合金退火样结晶度的比较(Ⅱ)

分别采用差示扫描量热分析(DSC)法和X-射线衍射分析(XRD)法测量了Ni74Si10B16非晶合金550℃等温退火21min，22min，23min与25min后的结晶度XC，并对其测量结果进行了讨论．确认通过DSC方法测量的非晶合金退火样结晶度，在一定程度上能较好地反映非晶合金晶化的程度，并且其测量精度与简便性优于XRD方法．而对于部分晶化非晶合金晶化相相含量的测量和分析表明：DSC法只能测量析出单相合金的相含量，对于析出多相合金的情况则不如XRD法有效．     

Forecasting of the Sr Modification Effects on Al-11.7%Si Alloy

The freezing curve of the Sr modificated Al-11.7%Si eutectic alloy is obtained by experiment,and the solid phase grow speed curve is calculated.The results show parameter that the maximum of solid phase grow speed is an effective parameter for describing Al-Si alloy modification,and the accurate forecasting on modification result can be realized by computer test. [WT5HZ]     

镁合金焦磷酸盐镀铜工艺的研究

镁合金上电镀耐蚀金属一般要经过电镀铜的过渡层以提高后镀金属的均镀性能和结合力.焦磷酸盐电镀铜是一种环保型电镀工艺,通过电镀锌后再电镀铜能获得结合力和致密性较高的镀层.镀锌液以硫酸锌为主盐,焦磷酸钾为配合剂,柠檬酸铵作辅助配合剂兼导电盐,电流密度2~3A.dm-2,温度在40℃时得到的锌镀层耐蚀性能较好,镀铜电流密度在0.5~2A.dm-2之间得出的镀层耐蚀性能较好.用研究的焦磷酸盐镀铜工艺代替氰化镀铜工艺作为过渡铜镀层的无氰镀工艺.     

Design and Development on Magnesium Alloys Database Based on Web

Based on web, an integrated magnesium alloys database system has been constructed, by adopting three-tier architecture and using advanced technologies such as ASP. In this database system, the user only owning a global browser can conveniently use this database system, which is a powerful tool to cut down the cost and time for developing new magnesium alloys.     

几种非晶态合金的交流磁性研究

本文研究了四种非晶态合金的磁性参数随频率ｆ及磁感应强度Ｂ的变化规律，得出非晶态合金的磁化过程符合晶态金属磁畴理论的技术磁化规律；在中强场内交流损耗符合晶态金属磁损耗分离关系，找出了Ｐ／ｆ与频率ｆ关系曲线包含两条直线规律，求得直线转折所对应的频率约为２０ｋＨｚ；不同铁磁性非晶态合金在最大磁导率μｍａｘ值相差较大的情况下，磁损耗分离满足相同的规律。