The Study Of Metal Material On Low Temperature Properties

Metal material applications on engineering become more widespread. Due to thetemperature low in the winter (especially in the Northeast)，that would result in somemechanical properties of metallic materials changed, then it would affect the safety andservice performance of metal materials. Firstly, three metal material45#, ZL201aluminum,40Cr on different temperatures (20℃,-20℃,-60℃) was studied that of tensile properties,elongation and reduction of area by universal testing machine. Then, the hardness andtoughness properties of three materials in different temperatures were explored by hardnesstester and impact tester. The morphology and characteristics of three materials in differenttemperatures were decided by optical microscopy and scanning electron microscopy.Studies have shown that1. As the temperature decreases, the tensile strength and yield strength of the threematerials have increased, but the45#and40Cr were more than ZL201aluminum alloy.2. As the temperature decreases, the reduction of area and elongation of the threematerials were reduced, indicating that when the temperature was lower, the plastic materialof three materials would be smaller.3. As the temperature decreases, the hardness of the three materials increased, but thechange did not happen in toughness. When the temperature was in-60℃, the toughness of45#decreased by30%,40Cr was12.7%. However ZL201aluminum did almost no change.So45#and40Cr metal material would be brittle in low temperature, however ZL201aluminum alloy material was not occur.4. We found that in20℃three materials generated ductile fracture, in-20℃, the45#generated brittle fracture, in-60℃40Cr also generated brittle fracture. However, ZL201aluminum always generated ductile fracture in all temperature, and this all by metallographyand electron microscopy.5. Although the40Cr appeared the phenomenon of low temperature brittleness, but itsductile-brittle transition temperature is lower than45#. So in low temperatures,45#was more easily broken than40Cr. This was the alloy contains some manganese, complex,titanium, vanadium and other alloying elements which was with carbon weak carbide, socarbon steel alloy has higher hardness, wear resistance, strength and toughness.