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A study of cooling rates during metallic glass formation in a hammer and anvil apparatus

 

作者: D. M. Kroeger,   W. A. Coghlan,   D. S. Easton,   C. C. Koch,   J. O. Scarbrough,  

 

期刊: Journal of Applied Physics  (AIP Available online 1982)
卷期: Volume 53, issue 3  

页码: 1445-1453

 

ISSN:0021-8979

 

年代: 1982

 

DOI:10.1063/1.330639

 

出版商: AIP

 

数据来源: AIP

 

摘要:

A model is presented of the simultaneous spreading and cooling of the liquid drop in a hammer and anvil apparatus for rapid quenching of liquid metals. The viscosity of the melt is permitted to vary with temperature, and to avoid mathematical complications which would be associated with spatial variation of the viscosity, Newtonian cooling is assumed. From an expression for the force required to spread the specimen, coupled equations for the mechanical energy balance for the system and the heat transfer from the sample to the hearth and hammer were obtained, and solved numerically. The sample reaches its final thickness when the force required to deform it becomes greater than the force exerted on it by the decelerating hammer. The model was fit to measurements of sample thickness versus hammer speed, using the interface heat transfer coefficient,h, as an adjustable parameter. The values ofhso obtained vary somewhat with the melt alloy/substrate metal combination. From predicted cooling curves, the effects of hammer speed, sample size, and initial melt temperature on the cooling rate and the efficiency of glass formation can be assessed. Addition of sample superheat shifts the cooling curve relative to the expected position of the time‐temperature‐transformation curve for formation of crystalline material from the melt, and thus is an effective means of increasing the probability of glass formation in this type of apparatus.

 

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