Why does this work? [C++; void pointer]

I thought I did something stupid - at least I thought it was. My question is: why does this work?

template<typename T>
class yarray
{
public:
    yarray() {
        pContainer = new T[1]; //initialize as array with size 1
        unCount = 0U; //counter
    }
    ~yarray() {
        delete[] pContainer; //cleanup
        pContainer = nullptr;
    }

    void push_back(T data)
    {
        ((T*)pContainer)[unCount] = data; //set (shouldn't it throw an exception when unCount > 0?
        unCount++; //increment
    }

    T operator[](const unsigned int & index)
    {
        if (index <= unCount)
            return ((T*)pContainer)[index];

        return T();
    }

private:
    void * pContainer;
    unsigned int unCount;
};

int main()
{
    yarray<int> klo;

    klo.push_back(342);
    klo.push_back(5563);

    for (auto i = 0; i < 2; ++i)
        std::cout << klo[i] << std::endl;
}

The code works perfectly in C++14 (Visual Studio). Shouldn't it throw an exception after the second push_back?

Update question: What if you don't initialize pContainer with new, but with pContainer = &T() instead? Doesn't that affect somehow the memory or even endanger other programs? When I use a class that prints out when it was constructed/destructed, all objects that were created will be destroyed right after the construction. Why can I use them even after destruction?