Thermal analysis

Merits of thermal analysis

No need of test pieces

A conventional method of melt quality evaluation was to make test pieces needing a considerable amount of labor and time. Melt thermal analysis has completely eliminated such extra work.

Quick analysis

Analysis results and suggestions for processing are given within five to seven minutes after sample pouring.

No individual bias

Full automatic analysis after pouring ,and hence, no individual bias.

Thermal analysis by ALT-I

A cooling curve and characteristic points

Data is obtained of the above characteristic points.

  • @ primary crystal undercooling temperature
  • A eutectic undercooling temperature
  • B primary crystal temperature
  • C eutectic temperature
  • D eutectic solidification time
  • E solidification time along liquidus

Drawing cooling curve

Temperature change from the start to the end of solidification of an aluminum alloy is converted to digital data and a cooling curve is drawn.
* Characteristic points are indicated in the cooling curve shown.

Evaluation from a cooling curve

From the primary and eutectic temperature and solidification time, various properties are evaluated: secondary dendrite arm spacing (DAS), Si%, eutectic Si refinement, alloy purity, and crystal size.
* For the characteristic points and their significance, refer to the section on “Principle of cooling curve and thermal analysis”.

Measurement of solidification rate

Dendrite arm spacing (DAS) can be evaluated from solidification rate.

Measurement of refinement

Effect of refiner is evaluated.

Measurement of Si%

Si% can be monitored.

Relationship between ALT-I and melt quality

Relation ship between thermal analysis and microstructure

Relationship between melt quality and microstructure

The photos below show structure refinement by Sr addition as compared with the original one in the left.

original melt
(without treatment)
melt after treatment
without@treatment treatment
Relationship between melt treatment and structure

Melt treatment and changed structure are reflected on the cooling curve where positions of primary temperature and eutectic temperature are changed from the original melt. Eutectic temperature is lowered in relation to the structural change.

original melt
(without treatment)
melt after treatment
Relationship between thermal analysis and structural image

The relationship between structure formation and cooling curve is evident from the above facts.

Relationship between Al-Si phase diagram and cooling curve

Shown below is a cooling curve of an alloy at an assumed concentration in the Al-Si phase diagram. Primary undercooling temperature and eutectic undercooling temperature in the cooling curve can be used in calculating Si% in relation to the phase diagram. Often in measuring a real melt primary, undercooling temperature and eutectic undercooling temperature appear as in this example.

Reducing scar and cost by the high precision thermal analysis system.

ALT-I has a high resolution of thermal analysis assisted by the use of the specific "Al cup".
The new thermal analysis accurately determines the characteristics of your melt.

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