Precision casting processing technology is more and more widely used in life, with more and more, among them, the cooling process is an important part of the process, and some want to experience the alloy solid phase transformation, phase transformation, become more metallic, for example, carbon delta relative to precision castings γ phase volume decreases to change, when γ the attack of eutectic phase transformation, the volume increases.

However, if the operating temperature of all parts of the casting is the same, there may be no microstructure stresses during the solid-phase transition, but only microenvironmental stresses. When the phase transition temperature is significantly higher than the critical temperature of the elastoplastic change, the alloy is in a plastic development state during the phase transition. Even if there is temperature control in all parts of the casting, the phase change stress will not be very large, and the enterprise will gradually decrease or even disappear.

If the pouring temperature is lower than the critical phase change temperature, and the temperature difference of the pouring site is low, and there is no time phase transition part, the microscopic phase transition stress will be caused due to different phase transition timings. The phase transition can be a residual stress or a stress of a temporary stress.

When casting a thin-walled structure in an epilepsy patient's solid phase transition, the thick-walled part is still in a plastic development condition, if the phase transformation volume of the new stage is greater than the volume of the old phase, the phase transformation of the parenchyma expands, and the thick-walled part of the plastic stretches of the enterprise, the result of the internal attack of the casting is only a small tensile stress, which can expand over time and gradually begin to disappear. In this social situation, if the quality of the casting continues to cool rapidly, the thick-walled parts will mainly undergo phase transformation and volume increase, because the thin-walled parts are already in an elastic working state, the thin-walled parts will be stretched by the inner elastic layer, forming tensile stress. Under such economic conditions, the residual phase transition temperature stress is opposite to the residual thermal stress sign and can be counteracted by interaction.

When the thin-walled part of the casting is released as a solid-phase transition, the thick-walled part is in an elastic state. When the relative capacity of the new phase is greater than that of the old phase, the thick-walled part is elastically stretched to form tensile stress, and the thin-walled part is elastically compressed to form temporary compressive stress. At this time, the phase change stress symbol is the same as the thermal stress symbol, that is, the stress is superimposed, and when the casting continues to cool to the thick-walled part, the specific volume increases and expands, so that the stress of the previous section disappears.

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