Effect Of Recasting On The Mechanical Properties Of The Non-precious Ceramic Alloy

Objective: To study the effect of recasting on the flexural properties of the non-precious ceramic alloy.Methods:⑴The non-precious ceramic alloys being cast for 1~4 times were achieved by casting the non-precious alloy cast in pressure casting condition for 1 time, 2 times, 3 times and 4 times respectively. By casting the alloys that hadn't been cast (new alloys) and that had been cast for 1~4 times separately, we get the castings of the flexural specimen, tensile specimen and microhardness specimen.⑵By using a universal tool grinder, the castings of flexural specimen were grind into flexural specimens with the same width and thickness. Then all of the flexural specimens endured a three-point bending load according to the ISO specification 7438 until ruptured, and the flexural strength and flexural modulus of each specimen was measured. (3) After the castings of tensile specimen were all earmarked, a static tensile test was used to evaluate their tensile strength, 0.2% yield strength and elongation, refer to the ISO specification 9693. (4) The castings of hardness specimen were grounded, enchased in resin and polished metallographically at first, and then a microhardness tester was used to measure their Vickers hardness.Results: (1) There is no significant decrease on the flexural strength and flexural modulus of the non-precious ceramic alloys that had been cast for 2~5 times, when comparing to that of the alloys being cast for just 1 time (P>0.05). Instead, the flexural strength of the alloys being cast for 3 or 5 times was significantly higher than that of the alloys being cast for 1 time (P<0.05), and the flexural modulus of the alloys being cast for 3 or 4 times was significantly higher than that of the alloys being cast for 1 time (P<0.05). (2) No significant decrease was found on the tensile strength, 0.2% yield strength and elongation of the non-precious ceramic alloys that had been cast for 2~5 times, when comparing to that of the alloys being cast for just 1 time (P>0.05). On the contrary, a significant increase was noticed on the elongation of the alloys being cast for 3 or 5 times (P<0.05). (3) On the Vickers hardness, there was no significant difference between the alloys being cast for 2~5 times and that being cast for 1 time (P>0.05).Conclusion: The non-precious ceramic alloy can be cast for 5 times at least, without causing its decrease of the flexural strength, flexural modulus, tensile strength, 0.2% yield strength, elongation and microhardness.